FSA Project Code: 
 
FS235003 (P01009) 
Cefas ref: 
 
C3027 


FSA Project Title: 
 
Investigation into the prevalence, distribution and levels of norovirus titre in oyster harvesting areas in the UK  

| Start Date:    |
|----------------|
| th             |
| September 2008 |


| End Date:    |
|--------------|
| st           |
| August 2011  |



Project Leader's Name: 
 
Dr James Lowther 


Institution: 
 
CEFAS Weymouth Laboratory The Nothe Barrack Road Weymouth DT4 8UB  



Date of submission: 

 
11th August 2011 


## Executive Summary

In this two year study, monthly samples of Pacific (*Crassostrea gigas*) or native oysters (*Ostrea edulis*) from 39 production areas around the UK were tested for norovirus genogroups I (GI) and II (GII) using a quantitative real-time RT-PCR 
method. All samples were also tested for *E. coli* using the regulatory reference method.  All sites sampled were designated and classified under EU Regulation 854/2004 and thus available for commercial production. Classifications ranged from class A to class C.  Sites included in the study were selected using a risk matrix score to ensure a representative selection of likely faecal contamination levels. Norovirus was detected in 76.2% (643/844 of samples), with similar prevalences in the two species of oysters tested (76.1% (468/615) for *C. gigas* and 76.4% (175/229) 
for *O. edulis*). There was a marked seasonality with a positivity rate of 90.0% (379/421) for samples taken between October and March compared with 62.4% (264/423) for samples taken between April and September. Quantification of positive samples revealed that the majority (52.1%; 335/643) were below the limit of quantification (100 detectable genome copies/g digestive tissues) for both genogroups. However a number of samples (1.4% of all positives; 9/463) contained levels in excess of 10,000 copies/g. As with prevalence, average quantities varied markedly between seasons, with highest levels detected between December and March. The scores for norovirus GI and GII in individual samples were significantly correlated with each other, however results for norovirus GII tended on average to be higher than those for GI. All 39 sites tested provided at least one norovirus positive result, although prevalence varied from 21% (5/24 samples) to 100% (20/20 samples). Norovirus levels varied markedly between sites with some sites scoring consistently over 1,000 copies/g during the winter while others rarely or never exceeded 100 copies/g. This study also examined relationships between norovirus contamination and potential risk indicators. A statistically significant correlation between norovirus levels and harvesting area classification was observed. Furthermore a statistically significant and predictive correlation was found between *E. coli* and norovirus levels when data was analysed by site rather than by sample. This finding provides support for the use of *E. coli* as an indicator organism for classification purposes. Strong correlations between norovirus contamination and environmental temperatures were also found on both a nationwide average and in the majority of cases a site-by-site basis. A statistically significant correlation was also observed between the site-specific risk scores initially assigned and the norovirus contamination levels observed in the study. We were able to further improve the predictive power of the risk matrix based on a combination of the *E. coli* contamination profile for the site and the seawater temperature at the time of sampling. This approach could assist risk management in relation to, for example, highlighting the need for virus monitoring or enhanced operator control measures. In summary the data generated in this study provides a systematic analysis of norovirus contamination in classified oyster production areas in the UK. The data will help to inform FSA policy on the reduction of viral contamination of bivalve molluscs and to instruct a coherent EU negotiating position. 

## Acknowledgements

This project was funded by the Food Standards Agency, UK. We would like to thank all participating oyster producers and local authority sampling officers for their cooperation and contributions, without which this project would not have been possible. 

In addition the Shellfish Association of Great Britain provided valuable assistance in recruiting participants.  
 
1 
Contents Executive summary Acknowledgements Contents List of Figures List of Tables 1.0  Introduction 2.0  
Aims and Objectives 

2 3.0  
Methods 


2 


3.1 
Sample collection 
2 


3.2  
Detection and quantification of GI and GII norovirus
2 


4 
3.3  
Detection and quantification of Escherichia coli 3.4  
Statistical analysis 
5 


4.0  
Comparison of native and Pacific oysters as a test matrix 
5 
 
 
4.1  
Introduction 
5 4.2  
Experimental approach 
5 
 
 
4.3  
Results  
6 
 
 
4.4  
Conclusion 
6 5.0 
Selection of oyster sites for surveillance 
7 
 
 
5.1 
Risk Assessment 
7 5.2 
Site selection 
8 6.0 
Surveillance results 
10 
 
 
6.1 
Prevalence of norovirus in tested samples 
10 6.2 
Levels of norovirus in tested samples 
11 6.3 
Comparison of project year 1 and year 2 
13 
 
 
| 6.4                                                        | Comparison of different sites                     | 13        |
|------------------------------------------------------------|---------------------------------------------------|-----------|
|                                                            |                                                   |           |
| 6.5                                                        | Comparison of different regions                   | 14        |
|                                                            |                                                   |           |
| 6.6                                                        | Comparison of different oyster species            | 15        |
|                                                            |                                                   |           |
| 6.7                                                        | Comparison                                        | of        |
|                                                            |                                                   |           |
|                                                            |                                                   |           |
| 16                                                         |                                                   |           |
| classifications                                            |                                                   |           |
|                                                            |                                                   |           |
| 6.8                                                        | Correlation of norovirus with                     |           |
| E. coli                                                    |                                                   |           |
|                                                            |                                                   |           |
| 6.9                                                        | Correlation of norovirus in oysters with clinical | 18        |
|                                                            |                                                   |           |
|                                                            |                                                   |           |
| laboratory reports                                         |                                                   |           |
|                                                            |                                                   |           |
| 6.10  Correlation                                          | of                                                | norovirus |
|                                                            |                                                   |           |
|                                                            |                                                   |           |
| 20                                                         |                                                   |           |
|                                                            |                                                   |           |
| 21                                                         |                                                   |           |
| environmental temperature data                             |                                                   |           |
|                                                            |                                                   |           |
| 6.11  Correlation of norovirus in oysters with risk scores |                                                   |           |
|                                                            |                                                   |           |
| 6.12  Further development of a risk scoring matrix         |                                                   |           |
|                                                            |                                                   |           |
| 7.0                                                        | Discussion                                        | 23        |
|                                                            |                                                   |           |
| 8.0                                                        | References                                        | 26        |
|                                                            |                                                   |           |
| 30                                                         |                                                   |           |
|                                                            |                                                   |           |
| Appendices                                                 |                                                   |           |
|                                                            |                                                   |           |
| 30                                                         |                                                   |           |
|                                                            |                                                   |           |
| 31                                                         |                                                   |           |
|                                                            |                                                   |           |
| Appendix 1 Oyster species comparison results               |                                                   |           |
|                                                            |                                                   |           |
| Appendix 2 Surveillance sample results                     |                                                   |           |
|                                                            |                                                   |           |
| Appendix 3 Statistical analysis                            | 62                                                |           |
|                                                            |                                                   |           |
|                                                            |                                                   |           |
|                                                            |                                                   |           |

## List Of Figures Figure 1: Recovery Of Norovirus Genogroup Ii From Aliquots Of

6 
native (*O. edulis*) and Pacific (*C. gigas*) oysters 
contaminated with faecal suspension. 
10 
 
Figure 2: 
Month-by-month percentages of samples positive for norovirus. Figure 3: 
Monthly geometric mean norovirus levels. 
12 
 
12 Figure 4: 
Monthly proportion of samples giving total norovirus 
results in different quantity brackets (copies/g). Figure 5: 
Month-by-month 
results 
for 
representative 
low, 
14 
medium and high norovirus sites. 
14 Figure 6: 
Monthly geometric mean norovirus levels for different UK regions. 
15 Figure 7: 
Within-site geometric means of individual sample norovirus scores grouped by UK region. 
15 Figure 8: 
Within-site geometric means of individual sample norovirus scores grouped by species. 
16 Figure 9: 
Within-site geometric means of individual sample norovirus scores grouped by classification. 
17 
 
17 
 
Figure 10:  Norovirus vs. *E. coli* for individual samples. 
 
Figure 11:  Norovirus vs. *E. coli*; comparison of within-site 
geometric means of individual sample scores (all months). 
18 
 
Figure 12:  Norovirus vs. *E. coli*; comparison of within-site 
geometric means of individual sample scores (October- March). Figure 13:  Comparison of monthly geometric mean norovirus 
19 
levels in oysters with lab reports received by the HPA. Figure 14:  Comparison of monthly geometric mean norovirus 
19 
levels in oysters with national average temperatures. Figure 15: Norovirus vs. seawater temperature; comparison of 
20 
individual sample norovirus scores with seawater temperatures at the time of sampling. 
 
| Figure 16: Norovirus vs. risk scores; comparison of within-site    | 21                                                        |
|--------------------------------------------------------------------|-----------------------------------------------------------|
| geometric means of individual sample norovirus                     |                                                           |
| scores with risk scores (England and Wales).                       |                                                           |
|                                                                    |                                                           |
|                                                                    |                                                           |
|                                                                    |                                                           |
| 22                                                                 |                                                           |
|                                                                    |                                                           |
|                                                                    |                                                           |
| Figure 17: Norovirus vs. sampling risk scores.                     |                                                           |
|                                                                    |                                                           |
| Figure 18: Proportion of samples giving total norovirus results in | 22                                                        |
| different quantity brackets (copies/g) for different               |                                                           |
| sampling risk scores.                                              |                                                           |
|                                                                    |                                                           |
|                                                                    |                                                           |
|                                                                    |                                                           |
| List of Tables                                                     |                                                           |
|                                                                    |                                                           |
| Table 1:                                                           | Risk based scoring system (risk matrix)                   |
|                                                                    |                                                           |
| 8                                                                  |                                                           |
|                                                                    |                                                           |
| Table 2:                                                           | Population cut-off for risk assessment of oyster sites in |
| Scotland                                                           |                                                           |
|                                                                    |                                                           |
|                                                                    |                                                           |
| 9                                                                  |                                                           |
|                                                                    |                                                           |
| Table 3:                                                           | Sites included in surveillance                            |
|                                                                    |                                                           |
| 10                                                                 |                                                           |
|                                                                    |                                                           |
| Table 4:                                                           | Two-by-two contingency table of samples testing           |
| positive and not detected for norovirus GI and GII                 |                                                           |
|                                                                    |                                                           |
| 11                                                                 |                                                           |
|                                                                    |                                                           |
| Table 5:                                                           | Two-by-two contingency table of positive and not          |
| detected samples taken during summer and winter                    |                                                           |
|                                                                    |                                                           |
| 11                                                                 |                                                           |
|                                                                    |                                                           |
| Table 6:                                                           | Number of samples giving norovirus results in different   |
| quantity brackets                                                  |                                                           |
|                                                                    |                                                           |
| 13                                                                 |                                                           |
|                                                                    |                                                           |
| Table 7:                                                           | Two-by-two contingency table of positive and not          |
| detected samples taken during project years 1 and 2                |                                                           |
|                                                                    |                                                           |
| 23                                                                 |                                                           |
|                                                                    |                                                           |
| Table 8:                                                           | Two-by-two contingency table of norovirus scores <100     |
| or >100 copies/g from samples with sampling risk                   |                                                           |
| scores <3.0 or >3.0                                                |                                                           |
|                                                                    |                                                           |
|                                                                    |                                                           |

## 1.0 Introduction

Contamination of bivalve shellfish with norovirus from human faecal sources is recognised as a major human health risk (Lees, 2000). Risk assessment and management currently relies on the use of *Escherichia coli* as an indicator of faecal 
(sewage) contamination in shellfish (Anon, 2004). However, this approach has been repeatedly demonstrated to inadequately contain the risk from human enteric viruses (Ang, 1998; Chalmers & McMillan, 1995; Gill *et al*., 1983). Over the last decade considerable progress has been made towards development of sensitive detection methods for norovirus in molluscan shellfish and there are numerous publications describing various approaches to virus testing (Höhne and Schreier, 2004; Jothikumar *et al*., 2005; Le Guyader *et al*., 2009; Loisy *et al*., 2005). All available methods are based on detection of virus genome using molecular techniques (PCR), as successful cultivation of norovirus by conventional virological techniques has been reported only rarely and is not feasible for application to foodstuffs. At present no internationally accepted reference method exists, however the European Committee on Normalisation (CEN) has an active working group, chaired by Cefas, addressing the development of a standard method for detection of norovirus and HAV in foodstuffs (including bivalve shellfish). A draft method is nearing completion (Lees and CEN WG6 TAG4, 2010) and this will be succeeded by an international method validation exercise. The timetable for publication of the CEN Technical Specification is 2012. EU legislative text foreshadows the adoption of virus controls when the methods are sufficiently developed and available for use (Anon, 2004; Anon, 2005). Thus it is possible that following publication of a CEN standard viral controls may be adopted into Community feed and food hygiene legislation. In preparation for possible legislative viral standards across the EU it has become essential to gain information about the practical application of the methods and potential impact on UK shellfisheries. Previously published and informal studies examining norovirus in UK oysters have revealed the presence of viral RNA in a significant proportion of samples, as well as indicating a clear seasonal pattern of contamination with higher prevalence and levels detected during the winter months from October to March (Lowther *et al*., 
2008; Lowther *et al*., 2010).  These studies have however all targeted specific production areas due to for example historical links to outbreaks of gastroenteritis, and the sampling plans were developed on an *ad hoc* basis according to the particular needs of the project. This project aimed to address these issues through application of a systematic sampling plan to oysters collected from a representative selection of UK oyster production sites and by testing these oysters for norovirus genogroups I and II using the most up-to-date quantitative methods based on the developing CEN standard. In this way the study seeks to generate systematic quantitative data on the occurrence, prevalence and levels of norovirus in UK production areas. The outputs of this project may help to inform FSA discussions with respect to reducing viral contamination of bivalve molluscs. 


## 2.0 Aims And Objectives

The aim of this project was to determine the rates of prevalence and typical levels of norovirus in oysters from a representative selection of sites from around the UK. The project also aimed to assess any seasonal variations and any relationships of norovirus levels with *E. coli* and other risk factors (such as population, environmental temperature, etc.). 3.0 
Methods 

## 3.1 Sample Collection

Samples were collected by the relevant local authority sampling officers in parallel to the collection of samples for the statutory classification monitoring programme. Sampling officers were asked to collect one sample per month of thirty oysters from each selected site from May 2009 to April 2011 inclusive. These were dispatched to the laboratory under temperature controlled conditions. Where practicable, water temperatures at the sampling site were taken using an approved method (http://www.cefas.defra.gov.uk/media/436986/samplingprotocolforlocalauthorities%5 b1%5d.pdf) at the time of sampling. 3.2 
Detection and quantification of GI and GII norovirus 3.2.1 Preparation of oyster homogenate Ten oysters from each sample under test were cleaned, opened and removed from their shells.  The peripheral flesh and organs of the animals were then cut away from the digestive gland and discarded. The glands of the oysters were pooled together then chopped finely with a razor-blade. A 2g portion of the chopped glands was added to a 50ml centrifuge tube for immediate testing and the remainder was retained frozen at -20ºC. A 10µl volume of Mengo virus strain vMC0 (to act as a process control) and 2ml of 100 μg/ml proteinase K solution (30U/mg; Promega) were then added to the chopped glands in the 50ml tube. The tube was then incubated at 37°C with shaking at 320 rpm for a duration of 1 hour, and subsequently incubated at 60°C for a duration of 15 min. The tube was centrifuged at 3000 x g for 5 min, then the soluble portion (homogenate) poured into a clean tube. Finally the volume of the homogenate was measured using a pipette, then it was retained at 4ºC for RNA purification and RT-PCR. 3.2.2 Purification of viral RNA 
Viral RNA extraction was carried out using NucliSens magnetic extraction technology (BioMerieux). For each sample a 500l aliquot of sample homogenate was added to 2ml NucliSens lysis buffer in a 15ml centrifuge tube. In addition for each batch of samples tested negative control and positive extraction control samples consisting of 500l water only and norovirus positive oyster homogenate (derived from bioaccumulated animals) respectively were also prepared and tested in parallel. Samples and controls were vortexed briefly then incubated at room temperature for 10 min before 50l magnetic silica was added to each tube and the samples incubated at room temperature for a further 10 min. The tubes were centrifuged at 1500 x g for 2 min and the supernatants removed by aspiration. The pelleted silica beads were resuspended in 400µl wash buffer 1 then transferred to individually labelled 1.5ml tubes on the MiniMag extraction station. The magnet of the MiniMag was raised to collect the silica beads on the walls of the tubes, then the beads washed for 30 secs using the wash function of the MiniMag. The supernatants were removed by aspiration, then the magnet lowered and the silica beads resuspended with 400µl of wash buffer 1, washed and the supernatant aspirated as before. The resuspension/wash/aspiration cycle was then repeated using 500µl wash buffer 2 then 500µl wash buffer 3 (wash for 15 secs only). The pelleted silica beads were then resuspended with 100µl of elution buffer. The tubes were capped and transferred to the thermoshaker at 60°C and shaken at 1400 rpm for 5 min, to allow elution of DNA and RNA from the silica beads. After elution the tubes were transferred to a portable magnet to collect the silica beads on the walls of the tubes, then the supernatant (sample nucleic acid (NA) extract) was transferred to a clean 0.5ml tube and stored at -20°C until required for reverse transcription. 3.2.3 One-step RT-PCR 
For GI QNIF4 (da Silva *et al.,* 2007), and NV1LCR primers (Svraka *et al.,* 2007), and TM9 probe (Höhne and Schreier, 2006) were used. For GII, QNIF2 (Loisy et al., 2005), and COG2R primers (Kageyama *et al.,* 2003), and QNIFS probe (Loisy et al., 2005) were used. For each sample or extraction control and both norovirus genogroups three aliquots of 5μl NA extract were added to adjacent wells of a 96- well optical reaction plate and made up to 25μl with (GI or GII) TaqMan reaction mix (final concentration of 1x each Ultrasense reaction mix, Rox reference dye and RNA Ultrasense enzyme mix (Invitrogen), 500 nM forward primer, 900 nM reverse primer, and 250 nM probe). Positive (dilution series prepared from a known concentration of plasmid carrying a copy of the target sequence) and negative (three aliquots of 5μl water only) PCR control materials were also tested. The plate was placed in a Stratagene Mx3005P real-time PCR machine with the following amplification program; 55°C for 60 min, then 95°C for 5 min, followed by 45 cycles of 95°C for 15 secs, 60°C for 1 min and 65C for 1 min. For analysis, threshold values were set at 0.20 fluorescence units, then threshold cycle (Ct) values were determined using the Mx3005P system software. Unexpected results in any positive or negative extraction or RT-PCR control triggered retesting of any affected samples. 

3.2.4 Quantification of norovirus using dsDNA standard curve analysis Norovirus titres were calculated based upon the principles of the forthcoming CEN standard method for quantification of viruses from CEN/TC275/WG6/TAG4. On each TaqMan run a log dilution series of dsDNA control corresponding to a range of approx 1 to 10,000 template copies/µl (quantified using spectrophotometry at 260nm) was included. The Ct values from this dilution series were then used to produce a standard curve. For each TaqMan replicate for the samples under test a quantity in copies/l was determined using the corresponding standard curve. Not detected replicates were ascribed a quantity of zero. The average quantities from the three replicates in each norovirus genogroup-specific TaqMan assay were calculated to give an overall quantity in detectable copies/µl NA extract for that sample and genogroup. This was multiplied by 100 to give detectable copies/test portion of homogenate (500µl), further multiplied by a factor based on the proportion of the complete homogenate tested, and finally divided by 2 to give a quantity in detectable genome copies/g digestive gland. This value does not take account of any losses during processing or RT-PCR inhibition and should be regarded as a minimum. 

Uncertainty of measurement of this method has been estimated at ±0.17 log10 
copies/g. 

 
3.2.5 Calculation of RT-PCR efficiency For each sample and each norovirus genogroup one aliquot of 5μl NA extract was added to a 96-well optical reaction plate and made up to 25μl with (GI or GII) TaqMan reaction mix (final concentrations as described above). A 1µl volume containing a high concentration of GI or GII RNA sequences (produced by *in vitro* 
transcription from the dsDNA control) was then added to each aliquot of sample NA extract in addition to a 5µl aliquot of water in a separate well. The plate was placed in a Stratagene Mx3005P real-time PCR machine and amplified using the program described above. The percentage RT-PCR efficiency for each sample and each gengroup was determined by comparing the Ct values for the sample NA extract plus control NA extract with that for the water plus control NA extract. Any sample with an RT-PCR efficiency of <25% was subjected to retesting, in the first instance by re-extracting the viral RNA from stored homogenate, then by testing stored digestive glands. Results for any sample providing three RT-PCR efficiency results of <25% were considered invalid and are recorded as "no result" in Appendix 3. 3.2.6 Calculation of extraction efficiency For each sample two aliquots of 5μl NA extract were added to adjacent wells of a 96- well optical reaction plate and made up to 25μl with Mengo virus-specific TaqMan reaction mix (final concentrations as described above). A dilution series prepared from the Mengo virus process control material was also tested. The plate was placed in a Stratagene Mx3005P real-time PCR machine and amplified using the program described above. The percentage extraction efficiency for each sample was determined by comparing the Ct values for the sample NA extract with those for the Mengo virus dilution series. Any sample with an extraction efficiency of <1% was subjected to retesting, in the first instance by re-extracting the viral RNA from stored homogenate, then by testing stored digestive glands. Results for any sample providing three extraction efficiency results of <1% were considered invalid and are recorded in Appendix 3 as "no result". 

3.2.7 Expression of results Samples where all three RT-PCR reactions for a given genogroup were negative are described as "not detected; <40 copies/g" in Appendix 3 (40 copies/g is the practical limit of detection of the method). Samples where the calculated quantity (as described above) was >500 copies/g are described as "positive; x copies/g" where x is the calculated quantity. Samples where the calculated quantity was between 100 and 500 copies/g are described as "positive; x copies/g" unless there were significant differences between results in individual RT-PCR reactions, in which case they are described as "positive; 100-500 copies/g". Samples where the calculated quantity was <100 copies/g (100 copies/g is the practical limit of quantification of the method) are described as "positive; <100 copies/g). 

 
3.3 
Detection and quantification of Escherichia coli 
 
3.3.1 Preparation of oyster homogenate Ten oysters from each sample under test were cleaned, opened and removed from their shells. The flesh was added to a blender with 2 volumes (per weight) of a 0.1% (w/v) solution of peptone (Oxoid) then homogenized using 4 bursts of 15 seconds at high speed. The homogenate was then retained at 4ºC for up to 24 hrs prior to enumeration.  
 
3.3.2 Enumeration of E. coli Oyster homogenates were assayed for *E. coli* using a standard most probable number method derived from ISO TS 16649-3. The homogenate was initially diluted using 0.1% (w/v) peptone to a concentration of 10% (v/v) ("neat"). A serial log10 
dilution series from neat to 10-2 was then prepared. Diluted homogenate was inoculated into five tubes containing mineral-modified glutamate broth (Oxoid) for each of the three dilutions and the tubes were then incubated at 37C for 18-24 hrs. Confirmation of acid producing tubes was carried out by subculture onto a chromogenic agar containing 5-bromo-4-chloro-3-indolyl--D glucoronide (LabM) and subsequent incubation at 44C for at further 18-24 hrs. Blue-green colonies indicative of the action of -glucoronidase activity were considered to be *E. coli* positive. The most probable number (MPN) was derived by reference to MPN tables contained within ISO 7218. The theoretical limit of detection of the assay was 20 MPN/100g shellfish and intravalvular fluid. 

3.4  
Statistical analysis All statistical analysis was carried out using Minitab 16 software. For the purposes of analysis samples giving not detected results for a particular norovirus genogroup were scored 20 copies/g for that genogroup (half the limit of detection (LOD) of 40 copies/g).  Samples giving positive results below the limit of quantification (LOQ; 100 copies/g) were scored 50 copies/g. For the purposes of figures and analyses where total counts of norovirus (GI and GII summed) were used, samples giving positive results <LOQ for both genogroup scored 100 copies/g; such results were included in the <100 copies/g bracket where such brackets were used. For *E. coli* samples giving results <20 MPN/100g were scored 10 MPN/100g. 4.0 
Comparison of native and Pacific oysters as a test matrix 

## 4.1 Introduction

Prior to this project the laboratory had previous experience of testing large numbers of samples of Pacific oysters (*Crassostrea gigas*) for norovirus using the detection methods described but had tested comparatively small numbers of samples of native oysters (*Ostrea edulis*). For this reason, prior to selection of sites for surveillance it was necessary to determine the suitability of the test method for use with both species of oysters. 4.2 
Experimental approach For both oyster species, a number of animals were opened and the digestive glands excised as described in section 3.1.1. Separately for each species, glands were pooled together until >10g was present, chopped finely with a razor-blade, and apportioned in 2g aliquots into five tubes. Each aliquot was artificially contaminated with an identical volume of norovirus GII positive faecal suspension, then subjected to Proteinase K treatment, RNA purification in duplicate and quantitative RT-PCR for GII as described in section 3.1. This procedure was repeated a total of three times using different contamination levels designed to result in approximate concentrations of 500,000, 50,000 and 5,000 copies/g respectively ("high", "medium" and "low"). 


## 4.3 Results

Quantities in copies/g were calculated for all extractions (see Appendix 1). Results for duplicate extractions from the same homogenate were then averaged (Figure 1). 

Two-way analysis of variance of the log10 transformed averaged data revealed that as expected contamination level had a significant impact on calculated quantities (p<0.001), however there was no significant difference between species (p=0.232), and there was also no significant interaction between species and contamination level (p=0.233; see Appendix 3 for statistical analysis). 4.4 
Conclusion Based on the data generated there was no evidence that the performance of the selected detection method varies significantly between the two oyster species of commercial significance in the UK. Both species were therefore included in the surveillance part of this project. 


## 5.0 Selection Of Oyster Sites For Surveillance 5.1 Risk Assessment

 
5.1.1  Introduction In this study risk scores were used to rank sites in order to provide a more scientific basis for sampling site selection. They should not be over-interpreted since the actual scores are susceptible to the weightings applied for each factor and for many risks the correct public health weighting cannot readily be established. In addition risk scores derived for England and Wales, and for Scotland, cannot be directly compared since it was necessary to use different population geographic factors (see below). Risk assessment was not carried out for sites in Northern Ireland due to the small number of potential candidate sites. 

 
5.1.2 England and Wales All active representative monitoring points (RMPs) with 75% or more sampling compliance in official control monitoring in the previous sampling year were selected for risk assessment (total 121 sites from 38 production areas). Each site was assigned a risk score based on a risk matrix as detailed in Table 1. 

 
Table 1: Risk based scoring system (risk matrix) 
 
Factor Low (score 1) 
Medium (score 3) 
High (score 5) 

| A/B/C, B/C or C       | 1                           | Classification status 2006    | A or unclassified    | A/B, B, B-LT or    |
|-----------------------|-----------------------------|-------------------------------|----------------------|--------------------|
| provisional           |                             |                               |                      |                    |
| classification        |                             |                               |                      |                    |
| 2                     | Classification status 2007  | As above                      | As above             |                    |
|                       |                             |                               |                      |                    |
| As above              |                             |                               |                      |                    |
|                       |                             |                               |                      |                    |
| 3                     | Classification status 2008  | As above                      |                      |                    |
|                       |                             |                               |                      |                    |
| As above              |                             |                               |                      |                    |
|                       |                             |                               |                      |                    |
| As above              |                             |                               |                      |                    |
|                       |                             |                               |                      |                    |
| 4                     | Changes                     | in                            | classification       | One in three years |
| status                |                             |                               |                      |                    |
| None (or change       |                             |                               |                      |                    |
| from not classified   |                             |                               |                      |                    |
| or provisional)       |                             |                               |                      |                    |
| Each                  | "very                       | high"                         |                      |                    |
| 5                     |                             |                               |                      |                    |
| Unusual               |                             |                               |                      |                    |
| E. coli               |                             |                               |                      |                    |
| results (per          |                             |                               |                      |                    |
| 100g) 2006            |                             |                               |                      |                    |
| 1                     |                             |                               |                      |                    |
|                       | result                      | relative                      | to                   |                    |
| Each "high" result    |                             |                               |                      |                    |
| relative to annual    |                             |                               |                      |                    |
| classification        |                             |                               |                      |                    |
| scores 3              |                             |                               |                      |                    |
| 2                     |                             |                               |                      |                    |
|                       |                             |                               |                      |                    |
| Class A 230-1,000     |                             |                               |                      |                    |
| Class                 | B                           | 4,600-                        |                      |                    |
| All results normal    |                             |                               |                      |                    |
| relative to annual    |                             |                               |                      |                    |
| classification        |                             |                               |                      |                    |
| scores 1              |                             |                               |                      |                    |
| Class A <230          |                             |                               |                      |                    |
| Class B <4,600        |                             |                               |                      |                    |
| Class C <10,000       |                             |                               |                      |                    |
| annual classification |                             |                               |                      |                    |
| scores 5              |                             |                               |                      |                    |
| Class A >1,000        |                             |                               |                      |                    |
| Class B >18,000       |                             |                               |                      |                    |
| 3                     |                             |                               |                      |                    |
|                       |                             |                               |                      |                    |
| Class C >18,000       | 18,000                      |                               |                      |                    |
| Class                 | C                           | 10,000-                       |                      |                    |
| 18,000                |                             |                               |                      |                    |
| As above              | As above                    |                               |                      |                    |
|                       |                             |                               |                      |                    |
| As above              |                             |                               |                      |                    |
|                       |                             |                               |                      |                    |
| 6                     |                             |                               |                      |                    |
| Unusual               |                             |                               |                      |                    |
| E. coli               |                             |                               |                      |                    |
| results (per          |                             |                               |                      |                    |
| 100g) 2007            |                             |                               |                      |                    |
|                       |                             |                               |                      |                    |
| As above              |                             |                               |                      |                    |
|                       |                             |                               |                      |                    |
| As above              |                             |                               |                      |                    |
|                       |                             |                               |                      |                    |
| As above              |                             |                               |                      |                    |
|                       |                             |                               |                      |                    |
| 7                     |                             |                               |                      |                    |
| Unusual               |                             |                               |                      |                    |
| E. coli               |                             |                               |                      |                    |
| results (per          |                             |                               |                      |                    |
| 100g) 2008            |                             |                               |                      |                    |
|                       |                             |                               |                      |                    |
| 8                     | Population in adjacent area |                               |                      |                    |
| 4                     |                             |                               |                      |                    |
| <200,000              | 200,000-399,999            |                               |                      |                    |
| 400,000               |                             |                               |                      |                    |
|                       |                             |                               |                      |                    |
| 9                     | Confirmed outbreaks         |                               |                      |                    |
| 5                     |                             |                               |                      |                    |
|                       | None                        | -                             | One or more in three |                    |
| years                 |                             |                               |                      |                    |
| 10                    | Unconfirmed outbreaks       |                               |                      |                    |
| 6                     |                             |                               |                      |                    |
|                       | None                        | Between one and               |                      |                    |
| three in three years  |                             |                               |                      |                    |
| More than three in    |                             |                               |                      |                    |
| three years           |                             |                               |                      |                    |

1 Split classifications considered at an equivalent annual classification, e.g. results for an A/B area judged against class B 
criteria. 

2 Where no results were taken site scored 3 for the year in question. 

5.1.3 Scotland 
Generation of risk data was carried out as part of FSAS SPIN 069 as previously described (Price-Hayward, 2010). All active production areas were selected for risk assessment (total 41 areas). Each area was assigned a risk score based on a risk matrix as detailed in Table 1, with the exception of different population cut-offs 
(Table 2) to take account of differences in population pressures. Table 2: Population cut-off for risk assessment of oyster sites in Scotland 
 
Factor 
Low (score 1) 
Medium (score 3) 
High (score 5) 
8 
Population in adjacent area1 
<600 
600-1,200 
1,200 
 

## 1Including All Census Areas Of Which At Least Part Lies Within 2Km Of The Sampling Point. 5.2 Site Selection 5.2.1 England And Wales A Total Of 31 Sites (20 Pacific And 11 Native Oysters, Table 3) Were Selected Using The Following Criteria.

1) sites with a broad range of risk scores 2) sites from a broad range of geographical locations 3) sites from a wide range of production areas; oyster production in England and 
Wales is concentrated on the South and East coasts so these regions are well represented 
 
5.2.2 Northern Ireland Two sites (both Pacific oysters) were selected in direct consultation with FSA Northern Ireland. 5.2.3 Scotland A total of 6 sites (all Pacific oysters) were selected using the same criteria as outlined above.  

|           |                                  |         | Site    | Risk           |
|-----------|----------------------------------|---------|---------|----------------|
| number    | Region                           | Species | score   | Classification |
| 1         |                                  |         |         |                |
|           |                                  |         |         |                |
| 1         | England - East Coast             |         |         |                |
| 2         |                                  |         |         |                |
|           |                                  |         |         |                |
| C. gigas  |                                  |         |         |                |
| 24        | B                                |         |         |                |
| 2         | England - East Coast             |         |         |                |
| C. gigas  |                                  |         |         |                |
| 23        | B                                |         |         |                |
| 3         | England - East Coast             |         |         |                |
| O. edulis |                                  |         |         |                |
| 16        | B                                |         |         |                |
| 4         | England - East Coast             |         |         |                |
| C. gigas  |                                  |         |         |                |
| 18        | B                                |         |         |                |
| 5         | England - East Coast             |         |         |                |
| C. gigas  |                                  |         |         |                |
| 25        | B                                |         |         |                |
| 6         | England - East Coast             |         |         |                |
| O. edulis |                                  |         |         |                |
| 20        | B                                |         |         |                |
| 7         | England - East Coast             |         |         |                |
| C. gigas  |                                  |         |         |                |
| 22        | B                                |         |         |                |
| 8         | England - East Coast             |         |         |                |
| C. gigas  |                                  |         |         |                |
| 18        | B                                |         |         |                |
| 9         | England - East Coast             |         |         |                |
| O. edulis |                                  |         |         |                |
| 22        | B                                |         |         |                |
| 10        | England - East Coast             |         |         |                |
| O. edulis |                                  |         |         |                |
| 12        | A                                |         |         |                |
| 11        | England - East Coast             |         |         |                |
| C. gigas  |                                  |         |         |                |
| 30        | C                                |         |         |                |
| 12        | England - East Coast             |         |         |                |
| C. gigas  |                                  |         |         |                |
| 20        | B                                |         |         |                |
| 13        | England - South Coast            |         |         |                |
| 3         |                                  |         |         |                |
|           |                                  |         |         |                |
| C. gigas  |                                  |         |         |                |
| 38        | B                                |         |         |                |
| 14        | England - South Coast            |         |         |                |
| O. edulis |                                  |         |         |                |
| 25        | C                                |         |         |                |
| 15        | England - South Coast            |         |         |                |
| C. gigas  |                                  |         |         |                |
| 22        | B                                |         |         |                |
| 16        | England - South Coast            |         |         |                |
| O. edulis |                                  |         |         |                |
| 20        | B                                |         |         |                |
| 17        | England - South Coast            |         |         |                |
| O. edulis |                                  |         |         |                |
| 27        | B                                |         |         |                |
| 18        | England - South Coast            |         |         |                |
| C. gigas  |                                  |         |         |                |
| 17        | B                                |         |         |                |
| 19        | England - South Coast            |         |         |                |
| C. gigas  |                                  |         |         |                |
| 14        | B                                |         |         |                |
| 20        | England - South Coast            |         |         |                |
| C. gigas  |                                  |         |         |                |
| 22        | B                                |         |         |                |
| 21        | England - South Coast            |         |         |                |
| C. gigas  |                                  |         |         |                |
| 14        | B                                |         |         |                |
| 22        | England - South Coast            |         |         |                |
| C. gigas  |                                  |         |         |                |
| 20        | B                                |         |         |                |
| 23        | England - South Coast            |         |         |                |
| O. edulis |                                  |         |         |                |
| 22        | B                                |         |         |                |
| 24        | England - South Coast            |         |         |                |
| O. edulis |                                  |         |         |                |
| 32        | B                                |         |         |                |
| 25        | England - South Coast            |         |         |                |
| O. edulis |                                  |         |         |                |
| 54        | B                                |         |         |                |
| 26        | England - West Coast, Wales & NI |         |         |                |
| 4,5       |                                  |         |         |                |
|           |                                  |         |         |                |
| C. gigas  |                                  |         |         |                |
| 12        | B                                |         |         |                |
| 27        | England - West Coast, Wales & NI |         |         |                |
| C. gigas  |                                  |         |         |                |
| 14        | B                                |         |         |                |
| 28        | England - West Coast, Wales & NI |         |         |                |
| C. gigas  |                                  |         |         |                |
| 20        | B                                |         |         |                |
| 29        | England - West Coast, Wales & NI |         |         |                |
| C. gigas  |                                  |         |         |                |
| n/a       | B                                |         |         |                |
| 30        | England - West Coast, Wales & NI |         |         |                |
| C. gigas  |                                  |         |         |                |
| 21        | B                                |         |         |                |
| 31        | England - West Coast, Wales & NI |         |         |                |
| C. gigas  |                                  |         |         |                |
| n/a       | A                                |         |         |                |
| 32        | England - West Coast, Wales & NI |         |         |                |
| O. edulis |                                  |         |         |                |
| 20        | B                                |         |         |                |
| 33        | England - West Coast, Wales & NI |         |         |                |
| C. gigas  |                                  |         |         |                |
| 18        | B                                |         |         |                |
| 34        | Scotland                         |         |         |                |
| C. gigas  |                                  |         |         |                |
| 32        | A                                |         |         |                |
| 35        | Scotland                         |         |         |                |
| C. gigas  |                                  |         |         |                |
| 36        | B                                |         |         |                |
| 36        | Scotland                         |         |         |                |
| C. gigas  |                                  |         |         |                |
| 16        | A                                |         |         |                |
| 37        | Scotland                         |         |         |                |
| C. gigas  |                                  |         |         |                |
| 50        | B                                |         |         |                |
| 38        | Scotland                         |         |         |                |
| C. gigas  |                                  |         |         |                |
| 20        | A                                |         |         |                |
| 39        | Scotland                         |         |         |                |
| C. gigas  |                                  |         |         |                |
| 26        | A                                |         |         |                |

1 For sites with seasonal classification, or where classification changed during the sampling period, the classification covering the majority of samples taken is shown. 

2 Coast of England from Eastern border with Scotland to North Foreland. 

3 Coast of England from North Foreland to Land"s End. 4 Coast of England and Wales from Land"s End to Western border with Scotland, plus coast of Northern Ireland. 5 Two sites without risk scores included to provide appropriate geographical coverage. 

## 6.0 Surveillance Results 6.1 Prevalence Of Norovirus In Tested Samples

Full results for each site are included in Appendix 2. Of 857 samples tested 844 
(98.5%) provided valid results (i.e. with acceptable extraction and amplification efficiencies) for norovirus GI and GII. Of these 844, 643 samples (76.2% [95% CI; 73.1-79.0%]) tested positive for norovirus; 402 (47.6% [95% CI; 44.2-51.1%]) were positive for both genogroups, 176 (20.9% [95% CI; 18.2-23.8%]) were positive for GI only and 65 (7.7% [95% CI; 6.0-9.8%]) were positive for GII only. Analysis of the twoby-two contingency table of positive and not detected results for GI and GII (Table 4) using Fisher"s exact test showed a highly significant difference between prevalence for the two genogroups (13.2% more GI positives; p<0.0001). Norovirus prevalence varied from month-to-month (Figure 2) ranging from a maximum of 100% positive (38/38 samples; 95% CI; 88.6-100%) in February 2010 to a minimum of 45.7% samples positive (16/35; 95% CI; 29.2-63.1%) in September 2010. Analysis of the two-by-two contingency table of positive and not detected samples from the summer months (April-September) and the winter months (October-March; Table 5) using Fisher"s exact test showed a highly significant difference between prevalence in the two seasons (27.6% higher in the winter; p<0.0001). 

|                                                                                    | Result               |
|------------------------------------------------------------------------------------|----------------------|
| 1                                                                                  |                      |
|                                                                                    |                      |
|                                                                                    | Positive             |
| 266 (31.5%)                                                                        |                      |
| Norovirus GI                                                                       |                      |
| 578 (68.5%)                                                                        |                      |
| [95% CI; 65.2-71.6%]                                                               | [95% CI; 28.4-34.8%] |
| 377 (44.7%)                                                                        |                      |
| Norovirus GII                                                                      |                      |
| 467 (55.3%)                                                                        |                      |
| [95% CI; 51.9-58.7%])                                                              | [95% CI; 41.3-48.1%] |
| 1                                                                                  |                      |
| Percentage of samples testing positive or not detected in period shown in brackets |                      |


|                                                                                    | Norovirus result     |
|------------------------------------------------------------------------------------|----------------------|
| 1                                                                                  |                      |
|                                                                                    |                      |
|                                                                                    | Positive             |
| 159 (37.6%)                                                                        |                      |
| Summer (April-September)                                                           |                      |
| 264 (62.4%)                                                                        |                      |
| [95% CI; 57.6-67.0%]                                                               | [95% CI; 33.0-42.4%] |
| 42 (10.0%)                                                                         |                      |
| Winter (October-March)                                                             |                      |
| 379 (90.0%)                                                                        |                      |
| [95% CI; 86.7-92.6%]                                                               | [95% CI; 7.4-13.3%]  |
| 1                                                                                  |                      |
| Percentage of samples testing positive or not detected in period shown in brackets |                      |

## 6.2 Levels Of Norovirus In Tested Samples

Levels of norovirus in tested samples varied widely. For norovirus GI the maximum recorded quantity was 16,507 copies/g and for GII it was 18,024 copies/g. However a large proportion of positive results (65.1% for GI [376/578 samples; 95% CI; 61- 68.9%] and 42.8% for GII [200/467; 95% CI; 38.3-47.5%]) were below the limit of quantification of the method (100 copies/g). The numbers and percentages of samples giving GI, GII and total norovirus results in different quantity brackets is shown in Table 6. 

|              | Number of samples in norovirus quantity brackets (copies/g)   |
|--------------|---------------------------------------------------------------|
| 1            |                                                               |
|              |                                                               |
| 1,000-10,000 |                                                               |
| Not detected |                                                               |
| <100         |                                                               |
| copies/g     |                                                               |
| 100-999      |                                                               |
| copies/g     | copies/g                                                      |
| >10,000      |                                                               |
| copies/g     |                                                               |
| 266 (31.5%)  | 376 (44.5%)                                                   |
| GI           | [95% CI;                                                      |
| 3 (0.4%)     |                                                               |
| [95% CI;     |                                                               |
| 28.4-34.8%]  | 41.2-48.0%]                                                   |
| 377 (44.7%)  | 200 (23.7%)                                                   |
| GII          | [95% CI;                                                      |
| 6 (0.7%)     |                                                               |
| [95% CI;     |                                                               |
| 41.3-48.1%]  | 20.9-26.8%]                                                   |
| 201 (23.8%)  | 335 (39.7%)                                                   |
| Sum          | [95% CI;                                                      |
| 9 (1.1%)     |                                                               |
| [95% CI;     |                                                               |
| 21.0-26.9%]  | 36.4-43.1%]                                                   |

1 Percentage of samples in given bracket shown in parentheses As with prevalence (see section 6.1), norovirus levels varied seasonally (Figure 3) with annual peaks occurring between December and March and lowest levels recorded between May and August. Levels of norovirus GII were on average higher than those for GI. Analysis of GI and GII levels for the same samples (samples testing positive for one or both genogroups only) using the Wilcoxon signed ranks test indicated that within samples GII levels were significantly higher than GI (p=0.000). In order to confirm that this result was not unduly affected by the arbitrary scores given to <LOD and <LOQ results, sensitivity analysis was carried out by repeating the Wilcoxon test after rescoring <LOD and <LOQ results as 40 and 100 copies/g respectively as well as after rescoring <LOD and <LOQ results as 0 and 1 copy/g respectively. In both cases differences between the two genogroups were still found to be significant (p=0.000). The Spearman"s rank correlation coefficient between norovirus GI and GII scores for individual samples (r=0.622) indicated that these two variables were significantly correlated (p=0.000).  
For each month of the project, the percentage of samples with total norovirus (GI plus GII summed) in different quantity brackets is shown in Figure 4. This figure illustrates the potential burden of different theoretical safety cut-offs for total norovirus on UK production areas at different times of year. 

## 6.3 Comparison Of Project Year 1 And Year 2

Overall prevalence, average levels and seasonal trends were broadly similar between the two years of the project (May 2009-April 2010 and May 2010-April 2011; Figures 2, 3 and 4). A greater proportion of samples tested positive in year 1 
(Table 7), however this difference was not significant when analysed using Fisher"s exact test (p=0.090). On the other hand average levels were higher in year 2 (geomean 175 copies/g (95% CI; 151-203 copies/g) for year 2 compared with 144 copies/g (95% CI; 126-164 copies/g) for year 1. Analysis of levels from year 1 and 2 using the Kruskal-Wallis test showed no significant difference between the genogroups however (p=0.513). 

|                              | Norovirus result   |
|------------------------------|--------------------|
| 1                            |                    |
|                              |                    |
|                              | Positive           |
| 337 (78.7%)                  | 91 (21.3%)         |
| Year 1 (May 2009-April 2010) |                    |
| [95% CI;                     | [95% CI;           |
| 74.5-82.5%]                  | 17.5-25.5%]        |
| 306 (73.6%)                  | 110 (26.4%)        |
| Year 2 (May 2010-April 2011) |                    |
| [95% CI;                     | [95% CI;           |
| 69-77.7%]                    | 22.3-31%]          |

1 Percentage of samples testing positive or not detected in period shown in brackets 

## 6.4 Comparison Of Different Sites

All 39 sites sampled during the project returned at least one positive result. Site-bysite prevalence varied from a minimum of 20.8% norovirus positive (5/24 samples [95% CI; 7.9-42.7%]) up to 100% positive (20/20 samples [95% CI; 80-100%]). Average norovirus levels varied very widely between sites, with the within-site geometric mean norovirus scores (GI and GII summed, samples not detected for both genogroups score 40) ranging from 50 (95% CI; 40-68 copies/g) - 2243 copies/g (95% CI; 883-5701 copies/g). To illustrate typical contamination patterns monthly results for three sites with comparatively low norovirus, three with medium norovirus and three with high norovirus are shown in Figure 5. 

Site 10 Site 20 Site 37 Site 31 Site 2 Site 5 Site 11 

## 6.5 Comparison Of Different Regions

The winter seasonality in the data set as a whole was also apparent when the different regions of the UK were examined separately, although average contamination levels varied (Figure 6). Average levels for sites in Scotland in particular seemed lower than for other regions. Within-site geometric mean norovirus scores grouped by region are shown in Figure 7. Median values for these sets ranged from 82 copies/g (Scotland [95% CI; 50-169 copies/g]) to 226 copies/g (England - East Coast [95% CI; 73-537 copies/g]) and comparison of the sets using the Kruskal-Wallis test revealed a significant difference in average norovirus contamination for tested sites for the four regions of the UK (p=0.029). Post hoc analysis using pairwise comparisons indicated that there were significant differences in average norovirus contamination between tested sites in Scotland and both England - East Coast and England - South Coast, but no differences between any of the other pairs. 

 

## 6.6 Comparison Of Different Oyster Species

The 39 sites analysed included 28 for Pacific oysters (*C. gigas*) and 11 for native oysters (*O. edulis*). The prevalence of norovirus in the two species was highly similar with 468 out of 615 *C. gigas* and 175 out of 229 *O. edulis* samples testing positive (76.1% [95% CI; 72.5-79.4%] and 76.4% [95% CI; 70.3-81.7%] respectively). Withinsite geometric mean norovirus scores grouped by species are shown in Figure 8. Comparison of the two sets using the Kruskal-Wallis test revealed no significant difference in median norovirus contamination for tested sites for the two species (p=0.901; *C. gigas* median = 165 copies/g [95% CI; 102-197 copies/g], O. edulis median = 174 copies/g [95% CI; 59-328 copies/g]). 

 

## 6.7 Comparison Of Shellfish Harvesting Area Classifications

The 39 sites analysed included 6 sites classified A for the majority of the sampling period, 31 sites classified B and 2 sites classified C. Within-site geometric mean norovirus scores grouped by classification are shown in Figure 9. Median values for these three sets increased with classification (82 copies/g [95% CI; 52-175 copies/g], 180 copies/g [95% CI; 116-209 copies/g] and 1,208 copies/g [range 174-2243 copies/g; too few measurements to calculate CI] for class A, B and C respectively) and comparison of the three sets using the Kruskal-Wallis test revealed a significant difference in average norovirus contamination for tested sites for the three classifications (p=0.018). Post hoc analysis using pairwise comparisons indicated that there were significant differences in average norovirus contamination between A and B and A and C classification sites, but not between B and C classification sites 
(although the analysis was confounded by the small number of C classification sites in the study). 


## 6.8 Correlation Of Norovirus With *E. Coli*

All 857 samples received were tested for *E. coli* (see section 3.3.2). One sample produced an invalid result (non-interpretable MPN tube combination on successive tests) however valid results were obtained for all other samples (n=856). In total 514 out of 856 samples (60.0% [95% CI; 56.7-63.3%]) contained levels which would be compliant with the end product standard (≤230 MPN/100g); the highest level recorded was 16,000 MPN/100g (found in 3 samples). Norovirus scores for individual samples plotted against the corresponding *E. coli* result are shown in Figure 10.  
As can be seen from Figure 10 a large number of samples returned low levels for norovirus and high levels for *E. coli*, or vice versa with little visual evidence of any correlation. Supporting this, the Spearman"s rank correlation coefficient between norovirus and *E. coli* scores on an individual sample basis was relatively low (r=0.195). However the existence of a significant interdependence of the two variables was strongly supported statistically (p=0.000). The rate of norovirus positivity for samples ≤230 MPN/100g was 73.9% (376/509 samples giving valid norovirus results; 95% CI; 69.8-77.6%); above this level it was 79.6% (266/334; 95% CI; 74.8-83.7%). 

Within-site geometric mean values for norovirus and *E. coli* are shown in Figure 11. 

The Spearman"s rank correlation coefficient was higher than for individual sample results (r=0.453), and indicated that these two variables were significantly correlated (p=0.004). When results from the winter months (October-March) were considered the strength of the relationship between norovirus and *E. coli* geometric mean values increased markedly (r = 0.676, p=0.000; Figure 12).  

## 6.9 Correlation Of Norovirus In Oysters With Clinical Laboratory Reports

Monthly geometric mean norovirus levels (both genogroups summed) for the samples tested in this study are shown in Figure 13 alongside monthly total numbers of laboratory reports of norovirus infections received by the Health Protection Agency from England and Wales and reported on their website, see e.g. http://www.hpa.org.uk/Topics/InfectiousDiseases/InfectionsAZ/Norovirus For the period of the study the two variables shared a common winter seasonality and the Spearman"s rank correlation coefficient between them (r=0.761) indicated that they were significantly correlated (p=0.000). However in contrast to the peak for norovirus in oyster samples, more lab reports were received by the HPA in the winter of 2009/10 than in the following winter (2010/11) although lab reports tend to be related to outbreaks associated with healthcare institutions and may not reflect the overall levels of norovirus in the community. 

 

## 6.10 Correlation Of Norovirus In Oysters With Environmental Temperature

Monthly geometric mean norovirus levels (both genogroups summed) for the samples tested in this study are shown in Figure 14 alongside monthly UK national average air temperatures (plotted with a reversed y axis to aid visualisation) as reported by the Met Office e.g. http://www.metoffice.gov.uk/climate/uk/actualmonthly For the period of the study the two variables shared a very strong, inverse, common seasonality (highest norovirus during periods of lowest air temperature) and the Spearman"s rank correlation coefficient between them (r=-0.877) indicated that they were significantly dependent (p=0.000). The maximum monthly geometric mean for norovirus in oysters (January 2011) followed shortly after the lowest monthly average air temperature of -1⁰C in December 2010. Seawater temperatures at the time of sampling were available for all or most samples for 36 out of 39 sites (for some sites seawater temperatures for a proportion of samples were missing due to particular issues, tides, problems with equipment etc. at the time of sampling). In order to investigate whether there was a common (although possibly variable) within-site correlation between temperature and norovirus Spearman"s rank analysis was carried out on data from each site. In 27 out of 36 sites there was a significant negative correlation between water temperature and norovirus levels (correlation coefficients of r=-0.460 to r=-0.879, see Appendix 3). For illustrative purposes Figure 15 shows norovirus scores plotted against seawater temperatures for samples from two sites where there was a particularly strong relationship. Of those sites where no statistically significant correlation was apparent the majority had low overall norovirus contamination levels (5 out of 9 with a within-site geometric mean norovirus score less than 100 copies/g). 

## 6.11 Correlation Of Norovirus In Oysters With Risk Scores

Figure 16 shows within-site geometric mean norovirus scores for sites in England and Wales plotted against the risk scores for these sites (as calculated in section 5.1.1 and detailed in Table 3; risk scores for sites in Scotland used a different matrix and are therefore not included in this analysis). The Spearman"s rank correlation coefficient between the two variables (r=0.546) indicated that they were significantly correlated (p=0.001), illustrating the value of the risk-based site selection method used.   

## 6.12 Further Development Of A Risk Scoring Matrix

The elaboration of a predictive matrix for norovirus risk could be a useful risk management tool. A correlation was found between the risk scoring matrix developed for site selection and norovirus geometric mean scores (see Figure 16). Further analysis attempted to improve the predictive potential of this approach using the data obtained in this study to develop the model. The existence of a significant within-site relationship between *E. coli* and norovirus scores, particularly during the winter, has been shown in section 6.8 (see Figure 12). In addition a correlation between seawater temperatures and norovirus scores for the majority of sites was found (section 6.10), while the seasonal variation in norovirus risk was clearly apparent (sections 6.1 and 6.2). We therefore elaborated an improved risk scoring system based on these factors as follows:- 
Factor a = within site geometric mean of *E. coli* scores from samples taken October-March (proxy for the overall norovirus risk of the site). Factor b = 20 - (seawater temperature at the time of sampling); a minimum baseline value of 1 was used for this factor such that seawater temperatures ≥19⁰C all score 1. Factor c = seasonal multiplier dependent on month of sampling as follows:- 

|      |     | May-August                       |     |      |     |   0.75  |
|------|-----|----------------------------------|-----|------|-----|---------|
|      |     | March, April, September, October |     | 1.00 |     |         |
|      |     | November-February                |     |      |     |    1.25 |

Risk score = (log10(product of factors a and b)) multiplied by factor c. 

Following this approach risk scores were calculated for all samples where seawater temperature data existed. These are plotted against norovirus scores in Figure 17. The Spearman"s rank correlation coefficient between the two variables (r=0.645) indicated that they were significantly correlated (p=0.000). 

The distribution of norovirus results in different quantity brackets according to sampling risk score is shown in Figure 18. Defining a norovirus score of >100 copies/g as a gold standard positive and a sampling risk score of >3.0 as a test outcome positive, this risk scoring system applied to the data in this study would have had an overall accuracy of 76.1% (95% CI; 72.7-79.2%), a sensitivity of 88.8% (95% CI; 84.1-92.2%), a specificity of 68.7% (95% CI; 64.1-72.9%), a positive predictive value of 62.2% (95% CI; 57.0-67.2%) and a negative predictive value of 91.3% (95% 
CI; 87.6-94.0%) (see Table 8).  

|            |               | Norovirus result    |
|------------|---------------|---------------------|
|            | <100 copies/g | >100 copies/g       |
| <3.0       |               |                     |
| 305        | 29            |                     |
| Sampling   |               |                     |
| risk score |               |                     |
| >3.0       |               |                     |
| 139        | 229           |                     |
|            |               |                     |
|            |               |                     |

## 7.0 Discussion

This study comprises the first systematic survey of the occurrence of norovirus in oyster production areas in the UK. The overall prevalence of samples testing positive for one or both norovirus genogroups was 76.2% (643/844). This was very similar for both oyster species tested in the study. GI norovirus was detected more frequently than GII (in 68.5% (578/844) and 55.3% (467/844) of samples respectively). This is in contrast to clinical samples where the overwhelming majority of norovirus outbreaks are caused by GII strains (Kroneman *et al*., 2008). However a greater frequency of norovirus GI in foodborne infections has previously been reported (Verhoef *et al*., 2010). Although relatively high prevalences (20-59%) have been recorded in several previous studies targeting oysters and other bivalve spp. (Costantini *et al*., 2006, Elamri *et al.*, 2006, Hansman *et al*., 2008, Loisy *et al*., 2005, Lowther *et al.*, 2008, Lowther *et al*., 2010) to the best of our knowledge the overall prevalence reported here is higher than that recorded in any other similar study. This may be due, at least in part, to progressive improvements in the sensitivity of the test method over recent years. It is also possible that the UK coastal environment is under greater population pressure and hence subject to more severe faecal contamination than other comparable countries. It is notable that within the different UK regions, norovirus levels appeared lowest in Scotland, where population pressures would be expected to be lowest.  
The significant proportion of positive samples highlights the importance of quantification for assessing the burden of norovirus contamination. Of samples testing positive, in the majority of cases (52.1%; 335/643) neither genogroup contained levels in excess of the limit of quantitation (LOQ) of the assay (100 copies/g). On the other hand for a small number of samples results of >10,000 copies/g were recorded. However, it should be noted that it is not currently possible to determine the absolute human health risks posed by different levels of norovirus. There is growing evidence of a dose response for norovirus in human volunteer studies (Teunis *et al*., 2008) and also evidence from a restaurant oyster consumption study of a correlation between norovirus levels in the batch consumed and likelihood of illness (Lowther *et al*., 2010). Several agencies (e.g. the European Food Safety Authority) are currently considering possible norovirus threshold levels for risk management. It was noted that different possible threshold levels have widely different impacts. For example a threshold level (GI and GII combined) of 100 copies/g would have resulted in a sample failure rate of >60% during the winter (October to March) for both years of the study. In contrast a threshold level of 1,000 copies/g would have resulted in a sample failure rate of <30%. The data presented in this study should prove valuable in determining the impacts of the use of such threshold levels for the UK. It should however be noted that oysters 
 
placed on the market in the UK generally receive additional commercial processing through depuration (self-purification) in tanks. Further processing is a legal requirement for class B and C oyster production areas and is also frequently applied to class A oysters. Although depuration is generally considered to be relatively ineffective for safeguarding against viral contamination (Doré *et al.*, 1995, Schwab et al., 1998, Muniain-Mujika *et al*., 2002) its contribution in reducing norovirus levels has not been systematically assessed, and this area may therefore warrant further investigation. Likewise a study of norovirus levels in oysters placed on the market following commercial processing would help establish the levels of exposure of the UK consumer. In common with previous studies in Northern Europe (Formiga-Cruz *et al*., 2002, LeGuyader *et al*., 2000, Lowther *et al.*, 2008) a very marked seasonality was observed, with highest prevalences and levels during the winter periods. Previously possible contributors to this seasonal pattern of occurrence have been suggested to include; the greater persistence of viral particles under typical Northern European winter environmental conditions of low solar irradiation, low temperature and higher turbidity (Allwood *et al*., 2005, Cannon *et al*., 2006); more effective viral clearance in oysters during summer months due to the higher rate of shellfish metabolism in warmer seawaters (Doré *et al*., 1998, Hernroth *et al*., 2007); and the higher prevalence of noroviruses in the human population, and thus seeded into the marine environment, during the winter (Blanton *et al*., 2006, Lopman *et al*., 2003, Mounts et al., 2000). Possibly all are contributory factors, however in this large systematic study the relationship of norovirus to environmental temperature data was found to be stronger than that with numbers of infections reported to national surveillance. Specifically, higher levels of norovirus were found in oysters in the second winter of the study period corresponding to the record low winter temperature but contrasting with a relatively low rate (compared with the first winter period) of lab reports of infections. However this may be due to limits in the surveillance systems currently in place to monitor human norovirus infections; lab reports tend to be related to outbreaks associated with healthcare institutions and may not reflect the overall levels of norovirus in the community. 

The findings related to seasonality are consistent with the winter seasonality of norovirus illness incidents following shellfish consumption in epidemiological data both for the UK and for other countries (Doré *et al*., 2000). During the early months of 2010 an exceptionally large number of incidents of gastroenteritis linked to oysters were reported from restaurants, hotels and similar establishments in the UK. In total for the period July 2009-June 2010, details of 53 clusters of norovirus-type illness associated with consumption of oysters were received by the Cefas Liaison for Outbreaks Associated with Bivalve Molluscs, compared with an average of 10.9 clusters per season (July-June) in 1999-2009 and a previous maximum of 26 clusters in 2005-2006 (personal communication). There were also high numbers of clusters reported in the same period from several other European countries (Westrell et al., 2010); this was linked to unusually severe weather conditions in northern Europe, for example the winter period of 2009-2010 (December to February) was officially the coldest in the United Kingdom since 1978-1979 (Met Office press release 1st March, 2010; 
http://www.metoffice.gov.uk/news/releases/archive/2010/coldest-uk-winter). 

 
On the other hand despite more extreme low temperatures in the following winter (December 2010 was the coldest on record in the UK; Met Office press release 5th January, 2011; http://www.metoffice.gov.uk/news/releases/archive/2011/cold-dec), and the corresponding high levels of norovirus in oysters found in this study, a relatively small number of illness clusters linked to oyster consumption were recorded (11 clusters from July 2010-June 2011; Cefas Liaison for Outbreaks Associated with Bivalve Molluscs, personal communication). It is possible that, following the unusually high number of clusters in the winter of 2009/10, some producers in the UK took steps to lower the risk of illness outbreaks, including voluntary restrictions on harvesting during the winter, and the use of extended depuration times, resulting in a lower number of illness incidents linked to oysters. In the past many outbreaks of norovirus have been linked to consumption of shellfish that were compliant with bacteriological faecal pollution criteria (Ang, 1998; Chalmers & McMillan, 1995; Gill *et al*., 1983). However analysis of the relationships between norovirus contamination, and either *E. coli* levels or classification status in this study offers support for the use of *E. coli* as an indicator organism for faecal pollution monitoring and risk management purposes. Although on an individual sample basis *E. coli* was poorly predictive of norovirus risk, on a site-specific basis average *E. coli* levels were found to correlate with average norovirus scores, particularly when data from the winter only was used. Significant differences were also found in norovirus levels in class A, B and C sites supporting the site specific classification approach. It should however be noted that class B is a very wide category accommodating *E. coli* levels of between 230 and 46,000 (in 10% of samples) MPN/100g shellfish. Based on the data presented in this study there is clearly scope to further refine the classification categories to improve the correlation with norovirus risk, for example by combining seasonal or temperature-based criteria with *E. coli*-based classification. A risk matrix incorporating various weighted factors (population density, *E. coli* scores, outbreak history etc.) was developed to aid site selection and ensure representative sampling in this study. It is informative that a positive correlation was found between the assigned risk score for each site and the average norovirus levels subsequently determined. Further analysis attempted to refine this risk ranking approach to improve the predictive value for norovirus contamination modelled using the data generated in this study. We have elaborated a risk scoring system based on a combination of the *E. coli* contamination profile of the site, the site seawater temperature, and the month of sampling. This system performed relatively well for the data generated in this study with, for example, a negative predictive value of 91.3%, although the positive predictive value of 62.2% indicates that it could be further improved. It would be interesting to validate this approach in a selection of areas not monitored during this study. A simple risk scoring matrix based on the principal factors identified here has the potential to focus enhanced risk management measures, such as virus monitoring or enhanced depuration practices, where they are most needed. In summary this is the first systematic study of norovirus contamination levels in UK oyster production areas and should help inform both the FSA and the producer sector with regard to this risk. It should also assist the FSA with consideration of the impact of possible norovirus threshold risk management levels. 


## 8.0 References

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Int. J. Environ. Res. Public Health. 2:442-446. Ang, L. H. 1998. An outbreak of viral gastroenteritis associated with eating raw oysters. *Commun. Dis. Pub. Health.* 1:38-40. Anon. 2004. Corrigendum to Regulation (EC) No 854/2004 of the European Parliament and of the Council of 29 April 2004 laying down specific rules for the organisation of official controls on products of animal origin intended for human consumption. *Official Journal of the European Union* L226 of 25 June 2004.  83-127. Anon. 2005. Commission Regulation (EC) No 2073/2005 of the European Parliament and of the Council of 15th November 2005 on microbiological criteria for foodstuffs. Official Journal of the European Union, L338, 1–26. Blanton L. H., S. M. Adams, R. S. Beard, G. Wei, S. N. Bulens, M. A. Widdowson, R. I. Glass, and S. S. Monroe. 2006. Molecular and epidemiologic trends of caliciviruses associated with outbreaks of acute gastroenteritis in the United States, 2000-2004. J. Infect. Dis. 193:413-421. Cannon, J. L., E. Papafragkou, G. W. Park, J. Osborne, L. A. Jaykus, and J. Vinje. 2006. Surrogates for the study of norovirus stability and inactivation in the environment: 
A 
comparison of murine norovirus and feline calicivirus. 

J. Food Prot. 69:2761-2765. Chalmers, J. W. T., and J. H. McMillan. 1995. An outbreak of viral gastroenteritis associated with adequately prepared oysters. *Epidemiol. Infect.* 115:163-167. Costantini V., F. Loisy, L. Joens, F. S. Le Guyader, and L. J. Saif. 2006. Human and animal enteric caliciviruses in oysters from different coastal regions of the United States. *Appl. Environ. Microbiol.* 72:1800-1809. da Silva A. K., J. C. Le Saux, S. Parnaudeau, M. Pommepuy, M. Elimelech, and F. S. Le Guyader. 2007. Evaluation of removal of noroviruses during wastewater treatment, using real-time reverse transcription-PCR: different behaviors of genogroups I and II. *Appl. Environ. Microbiol.* 73:7891-7897. Doré, W. J., and D. N. Lees. 1995. Behavior of *Escherichia coli* and male-specific bacteriophage in environmentally contaminated bivalve molluscs before and after depuration. *Appl. Environ. Microbiol.*, 61:2830-2834. Doré, W. J., K. Henshilwood, and D. N. Lees. 1998. The development of management strategies for control of virological quality in oysters. Water Sci. Technol. 38:29-35. Doré, W. J., K. Henshilwood, and D. N. Lees. 2000. Evaluation of F-specific RNA bacteriophage as a candidate human enteric virus indicator for bivalve molluscan shellfish. *Appl. Environ. Microbiol.* 66: 1280-1285. 

 
Elamri D. E., M. Aouni, S. Parnaudeau, and F. S. Le Guyader. 2006. Detection of human enteric viruses in shellfish collected in Tunisia. *Lett. Appl. Microbiol.* 43:399- 404. Formiga-Cruz, M., G. Tofino-Quesada, S. Bofill-Mas, D. N. Lees, K. Henshilwood, A. 

Allard, A. Conden-Hansson, B. Hernroth, A. Vantarakis, A. Tsibouxi, M. Papapetropoulou, M. Furones, and R. Girones. 2002. Distribution of human virus contamination in shellfish from different growing areas in Greece, Spain, Sweden, and the United Kingdom. *Appl. Environ. Microbiol.* 68:5990-5998. Gill, O. N., W. D. Cubitt, D. A. McSwiggan, B. M. Watney, and C. L. R. Bartlett. 1983. Epidemic of gastro-enteritis caused by oysters contaminated with small round structured viruses. *Br. Med. J.* 287:1532-1534. 

Hansman G. S., T. Oka, T. G. Li, O. Nishio, M. Noda, and N. Takeda. 2008. Detection of human enteric viruses in Japanese clams. *J. Food Prot.* 71:1689-1695. Hernroth, B., and A. Allard. 2007. The persistence of infectious adenovirus (type 35) in mussels 
(Mytilus edulis) 
and oysters 
(Ostrea edulis). 

Int. J. Food Microbiol. 113:296-302. Höhne, M., and E. Schreier. 2004. Detection and characterization of norovirus outbreaks in Germany: application of a one-tube RT-PCR using a fluorogenic realtime detection system. *J. Med. Virol.* 72:312-319. Jothikumar, N., J. A. Lowther, K. Henshilwood, D. N. Lees, V. R. Hill, and J. Vinjé. 2005. Rapid and sensitive detection of noroviruses using TaqMan-based one-step RT-PCR assays and application to clinical and naturally contaminated shellfish samples. *Appl. Environ. Microbiol.* 71:1870-1875. Kageyama T., S. Kojima, M. Shinohara, K. Uchida, S. Fukushi, F. B. Hoshino, N. Takeda, and K. Katayama. 2003. Broadly reactive and highly sensitive assay for Norwalk-like viruses based on real-time quantitative reverse transcription-PCR. J. 

Clin. Microbiol. 41:1548-1557. Kroneman A., L. Verhoef, J. Harris, H. Vennema., E. Duizer., Y. van Duynhoven, J. Gray., M. Iturriza., B. Böttiger, G. Falkenhorst, C. Johnsen, C. H. von Bonsdorff, L. Maunula., M. Kuusi, P. Pothier, A. Gallay, E. Schreier, M. Höhne, J. Koch, G. Szücs, G. Reuter, K. Krisztalovics, M. Lynch, P. McKeown, B. Foley, S. Coughlan, F. M. Ruggeri, I. Di Bartolo, K. Vainio, E. Isakbaeva, M. Poljsak-Prijatelj, A. H. Grom, J. Z. Mijovski, A. Bosch, J. Buesa, A. S. Fauquier, G. Hernandéz-Pezzi, K. O. Hedlund, and M. Koopmans. 2008. Analysis of integrated virological and epidemiological reports of norovirus outbreaks collected within the Foodborne Viruses in Europe network from 1 July 2001 to 30 June 2006. *J. Clin. Microbiol*. 46:2959-2965. Lees, D. N. 2000. Viruses and bivalve shellfish. *Int. J. Food Microbiol*. 59:81-116. Lees D. N. and CEN WG6 TAG4. 2010. International Standardisation of a Method for Detection of Human Pathogenic Viruses in Molluscan Shellfish. Food Environmental Virol., 2:146-155. 

Le Guyader, F., L. Haugarreau, L. Miossec, E. Dubois, and M. Pommepuy. 2000. Three-year study to assess human enteric viruses in shellfish. Appl. Environ. Microbiol. 66:3241-3248. Le Guyader F. S., S. Parnaudeau., J. Schaeffer, A. Bosch, F. Loisy, M. Pommepuy and R. L. Atmar. 2009. Detection and quantification of noroviruses in shellfish. Appl. Environ. Microbiol. 75:618-624. Loisy, F., R. L. Atmar, P. Guillon, P. Le Cann, M. Pommepuy, and F. S. Le Guyader. 2005. Real-time RT-PCR for norovirus screening in shellfish. *J. Virological Methods.* 123:1-7. Lopman B. A., M. H. Reacher, Y. Van Duijnhoven, F. X. Hanon, D. Brown, and M. 

Koopmans. 2003. Viral gastroenteritis outbreaks in Europe, 1995-2000. Emerg. Infect. Dis. 9:90-96. Lowther J. A., K. Henshilwood, and D. N. Lees. 2008. Determination of norovirus contamination in oysters from two commercial harvesting areas over an extended period, using semiquantitative real-time reverse transcription PCR. J. Food Prot. 71:1427-1433. Lowther J. A., J. M. Avant, K. Gizynski, R. E. Rangdale, and D. N. Lees. 2010. Comparison between quantitative real-time reverse transcription PCR results for norovirus in oysters and self-reported gastroenteric illness in restaurant customers. J. Food Prot. 73:305-311. Mounts A. W., T. Ando, M. Koopmans, J. S. Bresee, J. Noel, and R. I. Glass. 2000. Cold weather seasonality of gastroenteritis associated with Norwalk-like viruses. J. Infect. Dis. 181:S284-S287. Muniain-Mujika I., R. Girones, G. Tofiño-Quesada, M. Calvo, and F. Lucena. 2002. Depuration dynamics of viruses in shellfish. *Int. J. Food Microbiol.* 77:125-133. Price-Hayward, M. M. 2010.  An overview of sanitary surveys undertaken in Scotland. In: Lassus,PK. *et al* (eds.) Proceedings of the 7th International Conference on Molluscan Shellfish Safety, Nantes, France, June 14th-19th, 2009, pp 294-298. Schwab K. J., F. H. Neill, M. K. Estes, T. G. Metcalf, and R. L. Atmar. 1998. Distribution of Norwalk virus within shellfish following bioaccumulation and subsequent depuration by detection using RT-PCR. *J. Food Prot.* 61:1674-1680. Svraka S., E. Duizer, H. Vennema, E. de Bruin, B. van der Veer, B. Dorresteijn, and M. Koopmans. 2007. Etiological role of viruses in outbreaks of acute gastroenteritis in The Netherlands from 1994 through 2005. *J. Clin. Microbiol*. 45:1389-1394. Teunis P. F., C. L. Moe, P. Liu, S. E. Miller, L. Lindesmith, R. S. Baric, J. Le Pendu, and R. L. Calderon. 2008. Norwalk virus: how infectious is it? *J. Med. Virol.* 80:1468- 1476. Verhoef L., H. Vennema, W. van Pelt, D. Lees, H. Boshuizen, K. Henshilwood and M. Koopmans, 2010. Use of norovirus genotype profiles to differentiate origins of foodborne outbreaks. *Emerg. Infect. Dis.* 16:617-624. 

Westrell T., V. Dusch, S. Ethelberg, J. Harris, M. Hjertqvist, N. Jourdan-da Silva, A. Koller, A. Lenglet, M. Lisby, and L. Vold. 2010.  Norovirus outbreaks linked to oyster consumption in the United Kingdom, Norway, France, Sweden and Denmark, 2010. Eurosurveillance, 15(12). 


## Appendix 1: Oyster Species Comparison Results

|           |          | GII quantity (copies/g)    |
|-----------|----------|----------------------------|
|           |          |                            |
| O. edulis | C. gigas |                            |
|           | aliquot  | extraction 1               |
| 1         | 93454    | 333641                     |
| 2         | 181164   | 240309                     |
| High      |          |                            |
| 3         | 142665   | 185666                     |
| 4         | 138860   | 92330                      |
| 5         | 135668   | 207534                     |
| 1         | 26099    | 74961                      |
| 2         | 72738    | 168943                     |
| Medium    |          |                            |
| 3         | 32311    | 69099                      |
| 4         | 30796    | 72071                      |
| 5         | 68940    | 181471                     |
| 1         | 8508     | 6101                       |
| 2         | 16282    | 9318                       |
| Low       |          |                            |
| 3         | 24900    | 8082                       |
| 4         | 11994    | 7732                       |
| 5         | 10967    | 4913                       |

 

## Appendix 2: Surveillance Sample Results

Site 1 
  
  
  
  
  
  
  
  
Water 
Month 
temperature 
E. coli 
Norovirus GI 
Norovirus GII 
MAY 09 
12.5 
<20 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
JUN 09 
15.8 
50 
not detected 
<40 
copies/g 
positive 
<100 
copies/g 
JUL 09 
19 
<20 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
AUG 09 
20 
50 
not detected 
<40 
copies/g 
positive 
<100 
copies/g 
SEP 09 
17 
<20 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
OCT 09 
  
<20 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
NOV 09 
7.8 
490 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
DEC 09 
7.5 
330 
positive 
209 
copies/g 
positive 
100-500 
copies/g 
JAN 10 
1.6 
220 
positive 
119 
copies/g 
positive 
609 
copies/g 
FEB 10 
1.5 
50 
positive 
739 
copies/g 
positive 
1914 
copies/g 
MAR 10 
4 
790 
positive 
<100 
copies/g 
positive 
1882 
copies/g 
APR 10 
9.2 
<20 
not detected 
<40 
copies/g 
positive 
100-500 
copies/g 
MAY 10 
9.8 
130 
not detected 
<40 
copies/g 
positive 
<100 
copies/g 
JUN 10 
13.5 
20 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
JUL 10 
19.3 
<20 
not detected 
<40 
copies/g 
positive 
<100 
copies/g 
AUG 10 
18 
<20 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
SEP 10 
13.5 
<20 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
OCT 10 
10 
130 
positive 
11741 
copies/g 
positive 
<100 
copies/g 
NOV 10 
5.5 
50 
positive 
<100 
copies/g 
positive 
346 
copies/g 
DEC 10 
1 
170 
positive 
100-500 
copies/g 
positive 
658 
copies/g 
JAN 11 
2 
330 
positive 
260 
copies/g 
positive 
774 
copies/g 
FEB 11 
5.5 
700 
positive 
<100 
copies/g 
positive 
1745 
copies/g 
MAR 11 
3.5 
<20 
positive 
683 
copies/g 
positive 
1794 
copies/g 
APR 11 
12 
<20 
positive 
<100 
copies/g 
positive 
340 
copies/g 
  
  
  
  
  
  
  
  
  
 
 
Site 2 
  
  
  
  
  
  
  
  
Water 
Month 
temperature 
E. coli 
Norovirus GI 
Norovirus GII 
JUN 09 
16 
20 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
JUL 09 
20.9 
20 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
AUG 09 
21.5 
50 
positive 
<100 
copies/g 
positive 
211 
copies/g 
SEP 09 
16.5 
80 
positive 
<100 
copies/g 
positive 
170 
copies/g 
OCT 09 
13.5 
50 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
DEC 09 
7.5 
1700 
positive 
334 
copies/g 
positive 
100-500 
copies/g 
JAN 10 
4.2 
1700 
positive 
<100 
copies/g 
positive 
2554 
copies/g 
FEB 10 
2.8 
490 
positive 
371 
copies/g 
positive 
5743 
copies/g 
MAR 10 
6.4 
700 
positive 
<100 
copies/g 
positive 
4536 
copies/g 
APR 10 
9.9 
330 
positive 
<100 
copies/g 
positive 
656 
copies/g 
MAY 10 
10.6 
70 
positive 
<100 
copies/g 
positive 
100-500 
copies/g 
JUL 10 
16.5 
230 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
AUG 10 
18.8 
330 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
SEP 10 
15.4 
260 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
OCT 10 
9.6 
170 
positive 
574 
copies/g 
positive 
928 
copies/g 
DEC 10 
  
<20 
positive 
1920 
copies/g 
positive 
803 
copies/g 
JAN 11 
3.2 
490 
positive 
1116 
copies/g 
positive 
1990 
copies/g 
MAR 11 
11.5 
1100 
positive 
13193 
copies/g 
positive 
5138 
copies/g 
  
  
  
  
  
  
  
  
  
Site 3 
  
  
  
  
  
  
  
  
Water 
Month 
temperature 
E. coli 
Norovirus GI 
Norovirus GII 
MAY 09 
14.5 
<20 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
JUN 09 
18 
<20 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
JUL 09 
18.5 
20 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
SEP 09 
16.5 
20 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
OCT 09 
  
3500 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
NOV 09 
10.8 
50 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
DEC 09 
8 
130 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
JAN 10 
3.2 
20 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
FEB 10 
2.2 
1700 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
MAR 10 
4.8 
50 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
APR 10 
9.3 
20 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
MAY 10 
4 
<20 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
JUN 10 
18 
50 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
JUL 10 
17 
80 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
SEP 10 
10.8 
<20 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
OCT 10 
6.8 
<20 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
NOV 10 
6 
80 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
DEC 10 
1.5 
460 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
JAN 11 
3 
1700 
positive 
186 
copies/g 
not detected 
<40 
copies/g 
FEB 11 
6 
<20 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
MAR 11 
8.5 
330 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
APR 11 
14 
20 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
  
  
  
  
  
  
  
  
  


Site 4 
  
  
  
  
  
  
  
  
Water 
Month 
temperature 
E. coli 
Norovirus GI 
Norovirus GII 
MAY 09 
11.3 
20 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
JUN 09 
14.3 
<20 
not detected 
<40 
copies/g 
positive 
<100 
copies/g 
JUL 09 
18.8 
110 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
AUG 09 
20.2 
50 
not detected 
<40 
copies/g 
positive 
<100 
copies/g 
SEP 09 
14.8 
<20 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
OCT 09 
13.5 
50 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
NOV 09 
8 
<20 
positive 
<100 
copies/g 
positive 
100-500 
copies/g 
DEC 09 
7.8 
490 
positive 
203 
copies/g 
positive 
623 
copies/g 
JAN 10 
0.8 
490 
positive 
213 
copies/g 
positive 
1240 
copies/g 
FEB 10 
2 
70 
positive 
782 
copies/g 
positive 
3277 
copies/g 
MAR 10 
1.2 
3500 
positive 
1168 
copies/g 
positive 
1894 
copies/g 
APR 10 
8.5 
<20 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
MAY 10 
11 
<20 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
JUN 10 
12.5 
20 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
JUL 10 
18 
490 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
AUG 10 
18 
80 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
SEP 10 
12.2 
20 
not detected 
<40 
copies/g 
positive 
<100 
copies/g 
OCT 10 
9.8 
170 
positive 
<100 
copies/g 
positive 
100-500 
copies/g 
NOV 10 
4.8 
170 
positive 
100-500 
copies/g 
positive 
396 
copies/g 
DEC 10 
2 
80 
positive 
867 
copies/g 
positive 
1942 
copies/g 
JAN 11 
4.5 
790 
positive 
767 
copies/g 
positive 
3274 
copies/g 
FEB 11 
6.5 
70 
positive 
133 
copies/g 
positive 
1664 
copies/g 
MAR 11 
5 
<20 
positive 
1166 
copies/g 
positive 
2372 
copies/g 
APR 11 
10 
80 
positive 
288 
copies/g 
positive 
483 
copies/g 
  
  
  
  
  
  
  
  
  
 
 
Site 5 
  
  
  
  
  
  
  
  
Water 
Month 
temperature 
E. coli 
Norovirus GI 
Norovirus GII 
MAY 09 
  
80 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
JUN 09 
  
310 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
JUL 09 
  
460 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
AUG 09 
  
80 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
SEP 09 
  
170 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
OCT 09 
  
790 
positive 
150 
copies/g 
positive 
389 
copies/g 
NOV 09 
  
790 
positive 
180 
copies/g 
positive 
1012 
copies/g 
DEC 09 
  
230 
positive 
1042 
copies/g 
positive 
1981 
copies/g 
JAN 10 
  
700 
positive 
501 
copies/g 
positive 
10883 
copies/g 
FEB 10 
  
170 
positive 
953 
copies/g 
positive 
3841 
copies/g 
MAR 10 
  
2400 
positive 
1063 
copies/g 
positive 
10898 
copies/g 
APR 10 
  
230 
positive 
<100 
copies/g 
positive 
136 
copies/g 
MAY 10 
  
170 
positive 
172 
copies/g 
positive 
100-500 
copies/g 
JUN 10 
  
230 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
JUL 10 
  
330 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
AUG 10 
  
80 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
SEP 10 
  
70 
positive 
278 
copies/g 
positive 
<100 
copies/g 
OCT 10 
  
80 
positive 
648 
copies/g 
positive 
<100 
copies/g 
NOV 10 
  
790 
positive 
1153 
copies/g 
positive 
4919 
copies/g 
DEC 10 
  
790 
positive 
4625 
copies/g 
positive 
10820 
copies/g 
JAN 11 
  
330 
positive 
2615 
copies/g 
positive 
3657 
copies/g 
FEB 11 
  
330 
positive 
2890 
copies/g 
positive 
18025 
copies/g 
MAR 11 
  
790 
positive 
791 
copies/g 
positive 
1983 
copies/g 
APR 11 
  
230 
positive 
350 
copies/g 
positive 
838 
copies/g 
  
  
  
  
  
  
  
  
  
 
 
Site 6 
  
  
  
  
  
  
  
  
Water 
Month 
temperature 
E. coli 
Norovirus GI 
Norovirus GII 
MAY 09 
  
20 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
JUN 09 
  
1300 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
JUL 09 
  
330 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
AUG 09 
  
460 
not detected 
<40 
copies/g 
positive 
<100 
copies/g 
SEP 09 
  
230 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
NOV 09 
  
700 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
DEC 09 
  
230 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
JAN 10 
  
490 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
FEB 10 
  
80 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
MAR 10 
  
<20 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
APR 10 
  
20 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
MAY 10 
  
140 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
JUN 10 
  
230 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
AUG 10 
  
5400 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
SEP 10 
  
40 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
NOV 10 
  
20 
positive 
369 
copies/g 
not detected 
<40 
copies/g 
DEC 10 
  
50 
positive 
100-500 
copies/g 
positive 
<100 
copies/g 
JAN 11 
  
20 
positive 
100-500 
copies/g 
positive 
<100 
copies/g 
FEB 11 
  
80 
positive 
<100 
copies/g 
positive 
185 
copies/g 
MAR 11 
  
70 
positive 
172 
copies/g 
positive 
182 
copies/g 
APR 11 
  
20 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
  
  
  
  
  
  
  
  
  
Site 7 
  
  
  
  
  
  
  
  
Water 
Month 
temperature 
E. coli 
Norovirus GI 
Norovirus GII 
MAY 09 
10.4 
<20 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
JUN 09 
10.8 
80 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
JUL 09 
  
50 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
AUG 09 
20.4 
80 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
SEP 09 
17 
80 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
OCT 09 
16.2 
170 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
NOV 09 
9.5 
1300 
positive 
<100 
copies/g 
positive 
113 
copies/g 
DEC 09 
8.7 
790 
positive 
592 
copies/g 
positive 
405 
copies/g 
JAN 10 
  
230 
positive 
113 
copies/g 
positive 
348 
copies/g 
FEB 10 
3 
490 
positive 
<100 
copies/g 
positive 
100-500 
copies/g 
MAR 10 
  
490 
positive 
<100 
copies/g 
positive 
2548 
copies/g 
APR 10 
10 
20 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
MAY 10 
9.5 
330 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
JUN 10 
  
170 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
JUL 10 
17.6 
80 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
DEC 10 
3.6 
170 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
JAN 11 
5.1 
230 
positive 
315 
copies/g 
positive 
3944 
copies/g 
FEB 11 
  
80 
positive 
220 
copies/g 
positive 
1465 
copies/g 
MAR 11 
5.2 
230 
positive 
247 
copies/g 
positive 
1180 
copies/g 
APR 11 
9 
<20 
positive 
100-500 
copies/g 
positive 
279 
copies/g 
  
  
  
  
  
  
  
  
  
 
Site 8 
  
  
  
  
  
  
  
  
Water 
Month 
temperature 
E. coli 
Norovirus GI 
Norovirus GII 
MAY 09 
12 
80 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
JUN 09 
15 
140 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
JUL 09 
19 
2200 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
AUG 09 
20 
3500 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
SEP 09 
17 
230 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
OCT 09 
15 
40 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
NOV 09 
10 
110 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
DEC 09 
  
130 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
JAN 10 
3 
50 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
FEB 10 
3 
140 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
MAR 10 
7 
50 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
APR 10 
8 
310 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
MAY 10 
11 
<20 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
JUN 10 
  
130 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
JUL 10 
19 
230 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
AUG 10 
19 
790 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
SEP 10 
17 
70 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
OCT 10 
15.9 
790 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
NOV 10 
8 
40 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
DEC 10 
5 
220 
not detected 
<40 
copies/g 
positive 
100-500 
copies/g 
JAN 11 
5 
80 
positive 
115 
copies/g 
positive 
152 
copies/g 
FEB 11 
5.8 
130 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
MAR 11 
7.5 
<20 
not detected 
<40 
copies/g 
positive 
<100 
copies/g 
APR 11 
11 
20 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
  
  
  
  
  
  
  
  
  
 
 
Site 9 
  
  
  
  
  
  
  
  
Water 
Month 
temperature 
E. coli 
Norovirus GI 
Norovirus GII 
MAY 09 
12.1 
<20 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
JUN 09 
17 
20 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
JUL 09 
21 
220 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
AUG 09 
18 
330 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
SEP 09 
19 
50 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
OCT 09 
10 
330 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
NOV 09 
12 
490 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
DEC 09 
8.5 
490 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
JAN 10 
2.9 
1100 
positive 
1597 
copies/g 
positive 
100-500 
copies/g 
FEB 10 
3.5 
1300 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
MAR 10 
6 
50 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
APR 10 
12.5 
<20 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
MAY 10 
17 
50 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
JUN 10 
17.1 
80 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
JUL 10 
20.9 
70 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
AUG 10 
19 
50 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
SEP 10 
15 
50 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
OCT 10 
12 
80 
positive 
635 
copies/g 
positive 
<100 
copies/g 
NOV 10 
6 
80 
positive 
575 
copies/g 
positive 
824 
copies/g 
JAN 11 
6.2 
3500 
positive 
2043 
copies/g 
positive 
2739 
copies/g 
FEB 11 
1.8 
330 
positive 
571 
copies/g 
positive 
523 
copies/g 
MAR 11 
4.8 
130 
positive 
528 
copies/g 
positive 
134 
copies/g 
APR 11 
13.2 
20 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
  
  
  
  
  
  
  
  
  
 
 
Site 10 
  
  
  
  
  
  
  
  
Water 
Month 
temperature 
E. coli 
Norovirus GI 
Norovirus GII 
MAY 09 
13 
<20 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
JUN 09 
17.6 
<20 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
JUL 09 
19 
<20 
not detected 
<40 
copies/g 
positive 
<100 
copies/g 
AUG 09 
20.5 
<20 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
SEP 09 
16.5 
<20 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
OCT 09 
14.1 
20 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
NOV 09 
10.8 
20 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
DEC 09 
8.7 
<20 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
JAN 10 
3.2 
<20 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
FEB 10 
  
20 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
MAR 10 
5.8 
<20 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
APR 10 
9.8 
<20 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
MAY 10 
12.1 
<20 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
JUN 10 
16.6 
<20 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
JUL 10 
20 
20 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
AUG 10 
18.9 
<20 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
SEP 10 
17.9 
<20 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
OCT 10 
10.5 
<20 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
NOV 10 
8.5 
20 
not detected 
<40 
copies/g 
positive 
<100 
copies/g 
DEC 10 
3.8 
50 
positive 
171 
copies/g 
positive 
<100 
copies/g 
JAN 11 
6.2 
130 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
FEB 11 
6.4 
<20 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
MAR 11 
5.6 
<20 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
APR 11 
9.8 
<20 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
  
  
  
  
  
  
  
  
  
Site 11 
  
  
  
  
  
  
  
  
Water 
Month 
temperature 
E. coli 
Norovirus GI 
Norovirus GII 
JUN 09 
16 
490 
positive 
<100 
copies/g 
positive 
286 
copies/g 
JUL 09 
20.9 
3500 
not detected 
<40 
copies/g 
positive 
<100 
copies/g 
SEP 09 
16.3 
170 
positive 
741 
copies/g 
positive 
1163 
copies/g 
OCT 09 
13.1 
330 
positive 
<100 
copies/g 
positive 
690 
copies/g 
DEC 09 
7.5 
1100 
positive 
2190 
copies/g 
positive 
4949 
copies/g 
JAN 10 
4.2 
5400 
positive 
887 
copies/g 
positive 
13272 
copies/g 
FEB 10 
2.8 
940 
positive 
1124 
copies/g 
positive 
8380 
copies/g 
MAR 10 
6.4 
3500 
positive 
149 
copies/g 
positive 
6923 
copies/g 
APR 10 
9.9 
460 
positive 
<100 
copies/g 
positive 
3190 
copies/g 
MAY 10 
10.6 
170 
positive 
558 
copies/g 
positive 
1660 
copies/g 
JUL 10 
16.5 
1100 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
AUG 10 
18.4 
330 
positive 
378 
copies/g 
not detected 
<40 
copies/g 
SEP 10 
15.4 
170 
positive 
1379 
copies/g 
positive 
459 
copies/g 
OCT 10 
9.6 
790 
positive 
1649 
copies/g 
positive 
1287 
copies/g 
DEC 10 
  
<20 
positive 
4319 
copies/g 
positive 
2496 
copies/g 
JAN 11 
3.5 
490 
positive 
9385 
copies/g 
positive 
15369 
copies/g 
MAR 11 
11 
790 
positive 
16507 
copies/g 
positive 
5920 
copies/g 
  
  
  
  
  
  
  
  
  
 
Site 12 
  
  
  
  
  
  
  
  
Water 
Month 
temperature 
E. coli 
Norovirus GI 
Norovirus GII 
JUN 09 
15.2 
1700 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
JUL 09 
20.9 
330 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
AUG 09 
19 
170 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
SEP 09 
17 
230 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
OCT 09 
18.5 
490 
not detected 
<40 
copies/g 
positive 
<100 
copies/g 
NOV 09 
8.3 
140 
positive 
<100 
copies/g 
positive 
100-500 
copies/g 
DEC 09 
6.8 
490 
positive 
324 
copies/g 
positive 
<100 
copies/g 
FEB 10 
2.8 
790 
positive 
255 
copies/g 
positive 
2055 
copies/g 
MAR 10 
6.4 
230 
positive 
115 
copies/g 
positive 
5135 
copies/g 
APR 10 
9.9 
230 
positive 
<100 
copies/g 
positive 
177 
copies/g 
MAY 10 
10.6 
330 
positive 
131 
copies/g 
positive 
100-500 
copies/g 
JUL 10 
16.5 
130 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
AUG 10 
18.4 
230 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
SEP 10 
15.2 
330 
positive 
998 
copies/g 
positive 
798 
copies/g 
OCT 10 
9.6 
1300 
positive 
2268 
copies/g 
positive 
789 
copies/g 
JAN 11 
3.5 
790 
positive 
1301 
copies/g 
positive 
3114 
copies/g 
MAR 11 
11.5 
230 
positive 
1743 
copies/g 
positive 
1395 
copies/g 
  
  
  
  
  
  
  
  
  
Site 13 
  
  
  
  
  
  
  
  
Water 
Month 
temperature 
E. coli 
Norovirus GI 
Norovirus GII 
MAY 09 
  
2800 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
JUN 09 
  
1100 
not detected 
<40 
copies/g 
positive 
<100 
copies/g 
JUL 09 
  
2400 
not detected 
<40 
copies/g 
positive 
<100 
copies/g 
AUG 09 
  
1700 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
SEP 09 
  
3500 
no result 
  
no result 
  
 
 
OCT 09 
  
1300 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
NOV 09 
8.6 
2200 
no result 
  
no result 
  
 
 
DEC 09 
7.4 
230 
positive 
212 
copies/g 
positive 
3881 
copies/g 
JAN 10 
4.6 
700 
positive 
668 
copies/g 
positive 
1852 
copies/g 
FEB 10 
  
790 
positive 
123 
copies/g 
positive 
6127 
copies/g 
MAR 10 
11.5 
230 
positive 
<100 
copies/g 
positive 
100-500 
copies/g 
APR 10 
11.7 
220 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
MAY 10 
14.2 
220 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
JUN 10 
17.9 
790 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
JUL 10 
18.4 
330 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
AUG 10 
  
9200 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
SEP 10 
18.9 
5400 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
OCT 10 
15.1 
1100 
positive 
901 
copies/g 
positive 
<100 
copies/g 
NOV 10 
  
790 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
DEC 10 
10 
490 
positive 
<100 
copies/g 
positive 
239 
copies/g 
JAN 11 
7.3 
490 
positive 
479 
copies/g 
positive 
366 
copies/g 
FEB 11 
13.2 
1300 
positive 
168 
copies/g 
positive 
100-500 
copies/g 
MAR 11 
9.3 
220 
positive 
108 
copies/g 
positive 
125 
copies/g 
APR 11 
  
230 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
  
  
  
  
  
  
  
  
  
Site 14 
  
  
  
  
  
  
  
  
Water 
Month 
temperature 
E. coli 
Norovirus GI 
Norovirus GII 
MAY 09 
  
<20 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
JUN 09 
16 
20 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
JUL 09 
  
790 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
AUG 09 
  
1300 
not detected 
<40 
copies/g 
positive 
<100 
copies/g 
SEP 09 
17 
490 
positive 
<100 
copies/g 
positive 
119 
copies/g 
OCT 09 
16 
130 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
DEC 09 
9.5 
1100 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
JAN 10 
4.5 
5400 
positive 
3190 
copies/g 
positive 
6249 
copies/g 
FEB 10 
  
9200 
positive 
926 
copies/g 
positive 
3957 
copies/g 
MAR 10 
6.5 
40 
positive 
115 
copies/g 
positive 
1490 
copies/g 
APR 10 
7.5 
220 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
MAY 10 
10.5 
50 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
JUN 10 
15.5 
80 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
JUL 10 
19.5 
130 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
AUG 10 
  
330 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
SEP 10 
17 
2400 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
OCT 10 
15 
16000 
positive 
4794 
copies/g 
positive 
5042 
copies/g 
  
  
  
  
  
  
  
  
  
Site 15 
  
  
  
  
  
  
  
  
Water 
Month 
temperature 
E. coli 
Norovirus GI 
Norovirus GII 
MAY 09 
13.8 
<20 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
JUN 09 
17.9 
110 
no result 
  
no result 
  
 
 
JUL 09 
18.4 
80 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
AUG 09 
18.8 
50 
no result 
  
no result 
  
 
 
SEP 09 
17.7 
<20 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
OCT 09 
16.3 
50 
positive 
<100 
copies/g 
positive 
106 
copies/g 
NOV 09 
9.7 
20 
positive 
<100 
copies/g 
positive 
224 
copies/g 
DEC 09 
7.9 
1300 
positive 
<100 
copies/g 
positive 
326 
copies/g 
JAN 10 
5.3 
330 
positive 
179 
copies/g 
positive 
1123 
copies/g 
FEB 10 
  
230 
positive 
230 
copies/g 
positive 
637 
copies/g 
MAR 10 
  
170 
positive 
<100 
copies/g 
positive 
964 
copies/g 
APR 10 
10.5 
230 
positive 
155 
copies/g 
positive 
854 
copies/g 
MAY 10 
11.9 
130 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
JUN 10 
15 
230 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
JUL 10 
19.8 
<20 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
AUG 10 
18.3 
<20 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
SEP 10 
17.4 
790 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
OCT 10 
16.5 
700 
positive 
381 
copies/g 
positive 
<100 
copies/g 
NOV 10 
  
20 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
DEC 10 
5 
220 
positive 
<100 
copies/g 
positive 
513 
copies/g 
JAN 11 
5.4 
460 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
FEB 11 
4.5 
130 
positive 
<100 
copies/g 
positive 
312 
copies/g 
MAR 11 
  
130 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
APR 11 
12 
490 
positive 
192 
copies/g 
positive 
100-500 
copies/g 
  
  
  
  
  
  
  
  
  
Site 16 
  
  
  
  
  
  
  
  
Water 
Month 
temperature 
E. coli 
Norovirus GI 
Norovirus GII 
MAY 09 
13.1 
490 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
JUN 09 
16.4 
460 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
JUL 09 
18.5 
490 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
AUG 09 
19.6 
460 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
SEP 09 
16.9 
220 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
OCT 09 
14.9 
790 
positive 
<100 
copies/g 
positive 
100-500 
copies/g 
NOV 09 
11.8 
5400 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
DEC 09 
10 
230 
positive 
<100 
copies/g 
positive 
143 
copies/g 
JAN 10 
4.7 
260 
positive 
<100 
copies/g 
positive 
100-500 
copies/g 
FEB 10 
5.6 
80 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
MAR 10 
5.5 
170 
positive 
<100 
copies/g 
positive 
569 
copies/g 
APR 10 
  
230 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
MAY 10 
14 
50 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
JUN 10 
17.3 
230 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
JUL 10 
19.4 
2400 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
AUG 10 
18.6 
330 
positive 
100-500 
copies/g 
not detected 
<40 
copies/g 
OCT 10 
15.3 
330 
positive 
664 
copies/g 
positive 
<100 
copies/g 
NOV 10 
10.8 
3500 
positive 
401 
copies/g 
positive 
1640 
copies/g 
DEC 10 
5.8 
490 
positive 
884 
copies/g 
positive 
1225 
copies/g 
JAN 11 
6.8 
1700 
positive 
488 
copies/g 
positive 
1401 
copies/g 
FEB 11 
7.1 
330 
positive 
531 
copies/g 
positive 
558 
copies/g 
MAR 11 
8 
1300 
positive 
383 
copies/g 
positive 
1118 
copies/g 
APR 11 
6.5 
20 
positive 
865 
copies/g 
positive 
100-500 
copies/g 
  
  
  
  
  
  
  
  
  
 
 
Site 17 
  
  
  
  
  
  
  
  
Water 
Month 
temperature 
E. coli 
Norovirus GI 
Norovirus GII 
MAY 09 
13.2 
80 
not detected 
<40 
copies/g 
positive 
<100 
copies/g 
JUN 09 
16.2 
170 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
JUL 09 
18.1 
40 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
AUG 09 
19.7 
220 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
SEP 09 
17 
130 
not detected 
<40 
copies/g 
positive 
<100 
copies/g 
OCT 09 
15.3 
70 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
NOV 09 
11.8 
330 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
DEC 09 
10.7 
230 
positive 
240 
copies/g 
not detected 
<40 
copies/g 
JAN 10 
5.3 
3500 
positive 
102 
copies/g 
positive 
748 
copies/g 
FEB 10 
4.6 
50 
positive 
489 
copies/g 
positive 
1449 
copies/g 
MAR 10 
5.7 
490 
positive 
<100 
copies/g 
positive 
1009 
copies/g 
APR 10 
  
230 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
MAY 10 
14 
80 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
JUN 10 
16.6 
50 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
JUL 10 
19.4 
130 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
AUG 10 
18.3 
230 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
OCT 10 
  
40 
positive 
340 
copies/g 
positive 
835 
copies/g 
NOV 10 
11.2 
490 
positive 
<100 
copies/g 
positive 
316 
copies/g 
DEC 10 
6 
220 
positive 
100-500 
copies/g 
positive 
611 
copies/g 
JAN 11 
6.8 
700 
positive 
146 
copies/g 
positive 
414 
copies/g 
FEB 11 
7 
270 
positive 
161 
copies/g 
positive 
1120 
copies/g 
MAR 11 
  
220 
positive 
208 
copies/g 
positive 
759 
copies/g 
APR 11 
  
80 
positive 
251 
copies/g 
positive 
<100 
copies/g 
  
  
  
  
  
  
  
  
  
 
 
Site 18 
  
  
  
  
  
  
  
  
Water 
Month 
temperature 
E. coli 
Norovirus GI 
Norovirus GII 
MAY 09 
13.6 
170 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
JUN 09 
19.1 
<20 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
JUL 09 
16.3 
700 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
AUG 09 
17.5 
1300 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
SEP 09 
16.7 
110 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
OCT 09 
  
130 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
NOV 09 
  
<20 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
DEC 09 
10.1 
50 
positive 
195 
copies/g 
positive 
<100 
copies/g 
JAN 10 
  
<20 
positive 
487 
copies/g 
positive 
512 
copies/g 
FEB 10 
  
<20 
positive 
<100 
copies/g 
positive 
1223 
copies/g 
MAR 10 
6.1 
20 
not detected 
<40 
copies/g 
positive 
164 
copies/g 
APR 10 
11.5 
20 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
MAY 10 
13.2 
170 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
JUN 10 
16.8 
790 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
JUL 10 
15.1 
230 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
AUG 10 
17.3 
20 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
SEP 10 
  
130 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
OCT 10 
  
3500 
positive 
322 
copies/g 
positive 
340 
copies/g 
NOV 10 
  
70 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
DEC 10 
  
20 
positive 
331 
copies/g 
positive 
1468 
copies/g 
JAN 11 
8.1 
<20 
positive 
<100 
copies/g 
positive 
1312 
copies/g 
FEB 11 
9 
490 
positive 
786 
copies/g 
positive 
1158 
copies/g 
MAR 11 
  
230 
positive 
202 
copies/g 
positive 
835 
copies/g 
  
  
  
  
  
  
  
  
  
 
 
Site 19 
  
  
  
  
  
  
  
  
Water 
Month 
temperature 
E. coli 
Norovirus GI 
Norovirus GII 
MAY 09 
  
50 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
JUN 09 
  
<20 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
JUL 09 
  
50 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
AUG 09 
  
790 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
SEP 09 
  
80 
not detected 
<40 
copies/g 
positive 
<100 
copies/g 
OCT 09 
  
80 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
DEC 09 
  
2400 
positive 
1137 
copies/g 
positive 
905 
copies/g 
JAN 10 
  
130 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
FEB 10 
  
170 
not detected 
<40 
copies/g 
positive 
<100 
copies/g 
MAR 10 
  
<20 
not detected 
<40 
copies/g 
positive 
<100 
copies/g 
APR 10 
  
<20 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
MAY 10 
  
<20 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
JUN 10 
  
<20 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
JUL 10 
  
<20 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
AUG 10 
  
<20 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
SEP 10 
  
1700 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
NOV 10 
  
50 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
DEC 10 
  
330 
positive 
<100 
copies/g 
positive 
100-500 
copies/g 
JAN 11 
  
330 
positive 
<100 
copies/g 
positive 
465 
copies/g 
FEB 11 
  
130 
not detected 
<40 
copies/g 
positive 
185 
copies/g 
MAR 11 
  
330 
positive 
<100 
copies/g 
positive 
4089 
copies/g 
APR 11 
  
700 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
  
  
  
  
  
  
  
  
  
 
 
Site 20 
  
  
  
  
  
  
  
  
Water 
Month 
temperature 
E. coli 
Norovirus GI 
Norovirus GII 
JUN 09 
  
790 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
JUL 09 
  
2400 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
AUG 09 
  
2400 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
SEP 09 
  
3500 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
OCT 09 
  
1300 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
NOV 09 
8.6 
490 
no result 
  
no result 
  
 
 
DEC 09 
7.4 
330 
positive 
<100 
copies/g 
positive 
226 
copies/g 
JAN 10 
4.6 
330 
positive 
191 
copies/g 
positive 
1043 
copies/g 
FEB 10 
  
490 
positive 
<100 
copies/g 
positive 
933 
copies/g 
MAR 10 
11.5 
330 
positive 
<100 
copies/g 
positive 
838 
copies/g 
APR 10 
11.7 
330 
positive 
<100 
copies/g 
positive 
100-500 
copies/g 
MAY 10 
14.2 
70 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
JUN 10 
17.9 
790 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
JUL 10 
18.4 
1700 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
AUG 10 
  
2400 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
SEP 10 
18.9 
3500 
positive 
192 
copies/g 
not detected 
<40 
copies/g 
OCT 10 
15.1 
790 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
NOV 10 
  
790 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
DEC 10 
10 
790 
positive 
118 
copies/g 
positive 
320 
copies/g 
JAN 11 
7.3 
460 
positive 
445 
copies/g 
positive 
517 
copies/g 
FEB 11 
13.2 
330 
positive 
<100 
copies/g 
positive 
100-500 
copies/g 
MAR 11 
9.3 
490 
positive 
115 
copies/g 
positive 
<100 
copies/g 
APR 11 
  
790 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
  
  
  
  
  
  
  
  
  
Site 21 
  
  
  
  
  
  
  
  
Water 
Month 
temperature 
E. coli 
Norovirus GI 
Norovirus GII 
AUG 09 
14.3 
460 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
SEP 09 
14.6 
790 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
OCT 09 
15.4 
330 
no result 
  
no result 
  
 
 
DEC 09 
8.5 
110 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
JAN 10 
7.8 
1100 
positive 
278 
copies/g 
positive 
100-500 
copies/g 
FEB 10 
7.3 
<20 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
MAR 10 
6.7 
<20 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
MAY 10 
11.3 
20 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
JUN 10 
13.5 
<20 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
JUL 10 
15.6 
330 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
AUG 10 
15.9 
230 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
NOV 10 
13.1 
9200 
positive 
<100 
copies/g 
positive 
743 
copies/g 
DEC 10 
8.7 
1700 
positive 
<100 
copies/g 
positive 
534 
copies/g 
JAN 11 
8.5 
330 
positive 
720 
copies/g 
positive 
655 
copies/g 
FEB 11 
  
80 
positive 
296 
copies/g 
positive 
4075 
copies/g 
MAR 11 
9 
50 
positive 
<100 
copies/g 
positive 
124 
copies/g 
  
  
  
  
  
  
  
  
  


Site 22 
  
  
  
  
  
  
  
  
Water 
Month 
temperature 
E. coli 
Norovirus GI 
Norovirus GII 
MAY 09 
  
20 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
JUN 09 
  
330 
no result 
  
no result 
  
 
 
JUL 09 
  
330 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
AUG 09 
  
310 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
SEP 09 
11.8 
80 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
OCT 09 
14 
130 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
NOV 09 
11 
170 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
DEC 09 
8 
70 
positive 
114 
copies/g 
positive 
605 
copies/g 
JAN 10 
4 
130 
positive 
<100 
copies/g 
positive 
100-500 
copies/g 
FEB 10 
7 
20 
positive 
<100 
copies/g 
positive 
100-500 
copies/g 
MAR 10 
8 
130 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
APR 10 
8 
230 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
MAY 10 
10 
70 
not detected 
<40 
copies/g 
positive 
<100 
copies/g 
JUN 10 
14 
490 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
JUL 10 
18 
80 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
AUG 10 
18 
130 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
SEP 10 
17 
50 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
OCT 10 
15 
9200 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
NOV 10 
13 
490 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
DEC 10 
7 
210 
positive 
<100 
copies/g 
positive 
1967 
copies/g 
JAN 11 
7 
130 
not detected 
<40 
copies/g 
positive 
769 
copies/g 
FEB 11 
7 
50 
not detected 
<40 
copies/g 
positive 
392 
copies/g 
MAR 11 
  
70 
not detected 
<40 
copies/g 
positive 
669 
copies/g 
APR 11 
  
40 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
  
  
  
  
  
  
  
  
  
Site 23 
  
  
  
  
  
  
  
  
Water 
Month 
temperature 
E. coli 
Norovirus GI 
Norovirus GII 
MAY 09 
  
310 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
JUN 09 
17 
2800 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
JUL 09 
18.5 
790 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
AUG 09 
  
790 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
SEP 09 
17 
330 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
OCT 09 
16 
330 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
DEC 09 
9.5 
2200 
positive 
1311 
copies/g 
positive 
4736 
copies/g 
JAN 10 
4.5 
2400 
positive 
<100 
copies/g 
positive 
294 
copies/g 
FEB 10 
5 
330 
positive 
<100 
copies/g 
positive 
630 
copies/g 
MAR 10 
6.5 
490 
positive 
<100 
copies/g 
positive 
1088 
copies/g 
APR 10 
7.5 
460 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
MAY 10 
10 
16000 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
JUN 10 
15.5 
230 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
JUL 10 
19.5 
80 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
AUG 10 
19 
230 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
SEP 10 
17 
330 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
OCT 10 
15 
3500 
positive 
100-500 
copies/g 
positive 
100-500 
copies/g 
  
  
  
  
  
  
  
  
  
Site 24 
  
  
  
  
  
  
  
  
Water 
Month 
temperature 
E. coli 
Norovirus GI 
Norovirus GII 
JUL 09 
15.6 
9200 
positive 
<100 
copies/g 
positive 
140 
copies/g 
AUG 09 
15.8 
790 
positive 
<100 
copies/g 
positive 
137 
copies/g 
SEP 09 
14.8 
1700 
positive 
237 
copies/g 
positive 
206 
copies/g 
OCT 09 
14.5 
230 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
NOV 09 
12.2 
940 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
DEC 09 
10.4 
1700 
positive 
165 
copies/g 
positive 
<100 
copies/g 
JAN 10 
7.3 
170 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
FEB 10 
7 
490 
positive 
151 
copies/g 
positive 
<100 
copies/g 
MAR 10 
7.9 
230 
positive 
<100 
copies/g 
positive 
798 
copies/g 
APR 10 
8.8 
790 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
MAY 10 
10.3 
940 
not detected 
<40 
copies/g 
positive 
<100 
copies/g 
JUN 10 
15.4 
3500 
positive 
<100 
copies/g 
positive 
297 
copies/g 
JUL 10 
10 
490 
positive 
100-500 
copies/g 
not detected 
<40 
copies/g 
AUG 10 
16.6 
230 
positive 
548 
copies/g 
not detected 
<40 
copies/g 
SEP 10 
17 
270 
positive 
510 
copies/g 
positive 
<100 
copies/g 
OCT 10 
15.2 
2400 
positive 
757 
copies/g 
positive 
571 
copies/g 
NOV 10 
13.5 
5400 
positive 
504 
copies/g 
positive 
1108 
copies/g 
DEC 10 
7.5 
170 
positive 
423 
copies/g 
positive 
1561 
copies/g 
FEB 11 
8.9 
330 
positive 
109 
copies/g 
positive 
657 
copies/g 
MAR 11 
8.3 
1300 
positive 
<100 
copies/g 
positive 
1112 
copies/g 
  
  
  
  
  
  
  
  
  
Site 25 
  
  
  
  
  
  
  
  
Water 
Month 
temperature 
E. coli 
Norovirus GI 
Norovirus GII 
MAY 09 
13 
490 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
JUN 09 
18 
20 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
JUL 09 
19 
210 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
AUG 09 
20 
3500 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
SEP 09 
18 
170 
positive 
<100 
copies/g 
positive 
109 
copies/g 
NOV 09 
13 
2400 
positive 
<100 
copies/g 
positive 
637 
copies/g 
DEC 09 
9 
1100 
positive 
209 
copies/g 
positive 
<100 
copies/g 
JAN 10 
4 
3500 
positive 
218 
copies/g 
positive 
3638 
copies/g 
FEB 10 
4 
1300 
positive 
361 
copies/g 
positive 
3452 
copies/g 
MAR 10 
4 
2400 
positive 
639 
copies/g 
positive 
3505 
copies/g 
APR 10 
8 
330 
positive 
286 
copies/g 
positive 
157 
copies/g 
AUG 10 
18 
80 
positive 
139 
copies/g 
positive 
357 
copies/g 
SEP 10 
15 
330 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
NOV 10 
11 
5400 
positive 
100-500 
copies/g 
positive 
739 
copies/g 
DEC 10 
3 
130 
positive 
1178 
copies/g 
positive 
466 
copies/g 
JAN 11 
3 
130 
positive 
186 
copies/g 
positive 
235 
copies/g 
FEB 11 
8 
170 
positive 
286 
copies/g 
positive 
2606 
copies/g 
MAR 11 
12 
110 
positive 
151 
copies/g 
positive 
575 
copies/g 
APR 11 
13 
140 
positive 
519 
copies/g 
positive 
118 
copies/g 
  
  
  
  
  
  
  
  
  


Site 26 
  
  
  
  
  
  
  
  
Water 
Month 
temperature 
E. coli 
Norovirus GI 
Norovirus GII 
MAY 09 
13 
50 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
JUN 09 
8 
230 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
JUL 09 
16 
330 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
AUG 09 
12 
1300 
not detected 
<40 
copies/g 
positive 
<100 
copies/g 
SEP 09 
10 
330 
not detected 
<40 
copies/g 
positive 
<100 
copies/g 
OCT 09 
10 
2400 
not detected 
<40 
copies/g 
positive 
<100 
copies/g 
DEC 09 
9 
330 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
JAN 10 
2 
50 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
FEB 10 
4 
1300 
positive 
<100 
copies/g 
positive 
100-500 
copies/g 
MAR 10 
6 
90 
positive 
<100 
copies/g 
positive 
286 
copies/g 
APR 10 
7 
490 
not detected 
<40 
copies/g 
positive 
<100 
copies/g 
MAY 10 
10 
130 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
JUN 10 
11 
70 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
JUL 10 
11 
70 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
AUG 10 
12 
230 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
SEP 10 
10 
790 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
OCT 10 
9 
130 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
NOV 10 
  
490 
positive 
247 
copies/g 
positive 
669 
copies/g 
DEC 10 
-1 
50 
positive 
506 
copies/g 
positive 
<100 
copies/g 
JAN 11 
6 
110 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
FEB 11 
5 
130 
positive 
344 
copies/g 
positive 
872 
copies/g 
MAR 11 
4 
<20 
positive 
402 
copies/g 
positive 
332 
copies/g 
APR 11 
10 
<20 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
  
  
  
  
  
  
  
  
  
 
 
Site 27 
  
  
  
  
  
  
  
  
Water 
Month 
temperature 
E. coli 
Norovirus GI 
Norovirus GII 
MAY 09 
11 
<20 
not detected 
<40 
copies/g 
positive 
<100 
copies/g 
JUN 09 
13 
20 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
JUL 09 
12 
330 
not detected 
<40 
copies/g 
positive 
<100 
copies/g 
AUG 09 
  
1100 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
SEP 09 
10 
230 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
OCT 09 
11 
330 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
NOV 09 
14 
330 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
DEC 09 
12 
80 
positive 
147 
copies/g 
positive 
<100 
copies/g 
JAN 10 
9 
80 
positive 
120 
copies/g 
positive 
100-500 
copies/g 
FEB 10 
8 
<20 
positive 
102 
copies/g 
positive 
<100 
copies/g 
MAR 10 
7 
110 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
APR 10 
8 
<20 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
MAY 10 
14 
<20 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
JUN 10 
14 
80 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
JUL 10 
17 
50 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
AUG 10 
17 
170 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
SEP 10 
  
330 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
OCT 10 
15 
80 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
NOV 10 
13 
1300 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
DEC 10 
11 
50 
positive 
<100 
copies/g 
positive 
914 
copies/g 
JAN 11 
10 
130 
positive 
317 
copies/g 
positive 
2756 
copies/g 
FEB 11 
9 
80 
positive 
197 
copies/g 
positive 
1254 
copies/g 
MAR 11 
9 
<20 
positive 
<100 
copies/g 
positive 
191 
copies/g 
APR 11 
9.6 
50 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
  
  
  
  
  
  
  
  
  
 
 
Site 28 
  
  
  
  
  
  
  
  
Water 
Month 
temperature 
E. coli 
Norovirus GI 
Norovirus GII 
MAY 09 
11 
50 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
JUN 09 
13 
230 
not detected 
<40 
copies/g 
positive 
116 
copies/g 
JUL 09 
12 
5400 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
AUG 09 
17 
330 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
SEP 09 
16 
1100 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
OCT 09 
11 
<20 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
NOV 09 
14 
5400 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
DEC 09 
12 
130 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
JAN 10 
9 
460 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
FEB 10 
8 
50 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
MAR 10 
  
130 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
APR 10 
8 
130 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
MAY 10 
14 
220 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
JUL 10 
17 
170 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
AUG 10 
17 
490 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
SEP 10 
16 
230 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
OCT 10 
15 
2200 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
NOV 10 
13 
1700 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
DEC 10 
11 
80 
positive 
<100 
copies/g 
positive 
100-500 
copies/g 
JAN 11 
10 
490 
positive 
130 
copies/g 
positive 
532 
copies/g 
FEB 11 
9 
80 
positive 
<100 
copies/g 
positive 
985 
copies/g 
MAR 11 
9 
20 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
APR 11 
9.6 
<20 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
  
  
  
  
  
  
  
  
  
 
 
Site 29 
  
  
  
  
  
  
  
  
Water 
Month 
temperature 
E. coli 
Norovirus GI 
Norovirus GII 
MAY 09 
  
20 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
JUN 09 
15.1 
130 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
JUL 09 
19.9 
170 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
AUG 09 
  
230 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
SEP 09 
16.1 
5400 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
OCT 09 
15.3 
20 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
NOV 09 
10.1 
330 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
DEC 09 
8.5 
50 
positive 
109 
copies/g 
positive 
138 
copies/g 
JAN 10 
4 
<20 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
FEB 10 
5.6 
20 
positive 
<100 
copies/g 
positive 
327 
copies/g 
MAR 10 
8.9 
<20 
not detected 
<40 
copies/g 
positive 
<100 
copies/g 
APR 10 
11.5 
330 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
MAY 10 
16.2 
20 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
JUN 10 
18 
20 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
JUL 10 
21 
20 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
AUG 10 
17.5 
<20 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
SEP 10 
15.2 
230 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
OCT 10 
  
50 
not detected 
<40 
copies/g 
positive 
<100 
copies/g 
NOV 10 
6 
20 
positive 
265 
copies/g 
positive 
609 
copies/g 
DEC 10 
6.3 
130 
positive 
505 
copies/g 
positive 
100-500 
copies/g 
JAN 11 
6.1 
80 
positive 
238 
copies/g 
positive 
<100 
copies/g 
FEB 11 
7.2 
<20 
positive 
408 
copies/g 
positive 
287 
copies/g 
MAR 11 
10 
<20 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
APR 11 
10 
330 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
  
  
  
  
  
  
  
  
  
 
 
Site 30 
  
  
  
  
  
  
  
  
Water 
Month 
temperature 
E. coli 
Norovirus GI 
Norovirus GII 
MAY 09 
11 
<20 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
JUN 09 
13 
460 
not detected 
<40 
copies/g 
positive 
<100 
copies/g 
JUL 09 
12 
3500 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
AUG 09 
17 
790 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
SEP 09 
16 
330 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
OCT 09 
11 
80 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
NOV 09 
14 
790 
positive 
132 
copies/g 
positive 
<100 
copies/g 
DEC 09 
12 
230 
positive 
184 
copies/g 
positive 
100-500 
copies/g 
JAN 10 
9 
630 
positive 
<100 
copies/g 
positive 
100-500 
copies/g 
FEB 10 
8 
130 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
MAR 10 
  
20 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
APR 10 
8 
340 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
MAY 10 
14 
330 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
JUN 10 
14 
130 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
JUL 10 
17 
490 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
AUG 10 
17 
1100 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
SEP 10 
16 
2400 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
OCT 10 
15 
460 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
NOV 10 
13 
230 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
DEC 10 
11 
230 
positive 
<100 
copies/g 
positive 
462 
copies/g 
JAN 11 
10 
490 
positive 
138 
copies/g 
positive 
824 
copies/g 
FEB 11 
9 
20 
positive 
<100 
copies/g 
positive 
100-500 
copies/g 
MAR 11 
9 
<20 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
APR 11 
9.6 
20 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
  
  
  
  
  
  
  
  
  
 
 
Site 31 
  
  
  
  
  
  
  
  
Water 
Month 
temperature 
E. coli 
Norovirus GI 
Norovirus GII 
MAY 09 
12 
<20 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
JUN 09 
12.8 
<20 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
JUL 09 
14 
130 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
AUG 09 
14 
3500 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
SEP 09 
14 
490 
no result 
  
no result 
  
 
 
OCT 09 
13 
230 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
NOV 09 
12 
330 
positive 
<100 
copies/g 
positive 
417 
copies/g 
DEC 09 
11 
20 
positive 
100-500 
copies/g 
positive 
1240 
copies/g 
JAN 10 
11 
<20 
positive 
396 
copies/g 
positive 
1140 
copies/g 
FEB 10 
6 
<20 
positive 
<100 
copies/g 
positive 
626 
copies/g 
MAR 10 
8.1 
20 
positive 
<100 
copies/g 
positive 
100-500 
copies/g 
APR 10 
10.1 
<20 
not detected 
<40 
copies/g 
positive 
<100 
copies/g 
MAY 10 
11 
<20 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
JUN 10 
12 
50 
no result 
  
no result 
  
 
 
JUL 10 
13 
<20 
not detected 
<40 
copies/g 
positive 
<100 
copies/g 
AUG 10 
15 
40 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
SEP 10 
13 
20 
positive 
100-500 
copies/g 
not detected 
<40 
copies/g 
OCT 10 
10 
<20 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
NOV 10 
8 
20 
positive 
277 
copies/g 
positive 
126 
copies/g 
DEC 10 
1 
80 
positive 
167 
copies/g 
positive 
474 
copies/g 
JAN 11 
8 
<20 
positive 
519 
copies/g 
positive 
<100 
copies/g 
FEB 11 
  
20 
positive 
204 
copies/g 
positive 
586 
copies/g 
MAR 11 
  
<20 
positive 
157 
copies/g 
positive 
100-500 
copies/g 
APR 11 
  
<20 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
  
  
  
  
  
  
  
  
  
 
 
Site 32 
  
  
  
  
  
  
  
  
Water 
Month 
temperature 
E. coli 
Norovirus GI 
Norovirus GII 
MAY 09 
12 
2400 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
JUN 09 
12 
50 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
JUL 09 
12 
490 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
AUG 09 
12 
460 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
SEP 09 
12 
16000 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
OCT 09 
12 
490 
positive 
393 
copies/g 
positive 
751 
copies/g 
DEC 09 
12 
80 
positive 
218 
copies/g 
positive 
100-500 
copies/g 
MAR 10 
7 
170 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
APR 10 
  
790 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
MAY 10 
11 
<20 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
JUN 10 
13 
170 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
JUL 10 
14 
700 
positive 
147 
copies/g 
not detected 
<40 
copies/g 
AUG 10 
14 
1100 
positive 
124 
copies/g 
not detected 
<40 
copies/g 
SEP 10 
12 
80 
positive 
100-500 
copies/g 
not detected 
<40 
copies/g 
OCT 10 
  
790 
positive 
199 
copies/g 
positive 
<100 
copies/g 
NOV 10 
12 
790 
positive 
278 
copies/g 
positive 
270 
copies/g 
DEC 10 
11 
790 
positive 
1625 
copies/g 
positive 
743 
copies/g 
JAN 11 
10 
void 
positive 
256 
copies/g 
positive 
<100 
copies/g 
FEB 11 
10 
70 
positive 
<100 
copies/g 
positive 
203 
copies/g 
APR 11 
10 
50 
positive 
256 
copies/g 
positive 
306 
copies/g 
  
  
  
  
  
  
  
  
  
 
 
Site 33 
  
  
  
  
  
  
  
  
Water 
Month 
temperature 
E. coli 
Norovirus GI 
Norovirus GII 
MAY 09 
11.6 
130 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
JUN 09 
17.2 
2400 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
JUL 09 
17.5 
700 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
AUG 09 
17 
130 
no result 
  
no result 
  
 
 
SEP 09 
15.6 
330 
positive 
224 
copies/g 
positive 
722 
copies/g 
OCT 09 
14.8 
490 
positive 
<100 
copies/g 
positive 
358 
copies/g 
NOV 09 
10.7 
460 
positive 
<100 
copies/g 
positive 
1328 
copies/g 
DEC 09 
8 
2400 
positive 
<100 
copies/g 
positive 
2651 
copies/g 
JAN 10 
4 
80 
positive 
126 
copies/g 
positive 
1869 
copies/g 
FEB 10 
5 
490 
positive 
2952 
copies/g 
positive 
2714 
copies/g 
MAR 10 
4.5 
110 
positive 
214 
copies/g 
positive 
2718 
copies/g 
APR 10 
11 
490 
positive 
<100 
copies/g 
positive 
146 
copies/g 
MAY 10 
16.9 
790 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
JUN 10 
13.2 
1300 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
JUL 10 
17 
1700 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
SEP 10 
16.1 
460 
positive 
<100 
copies/g 
positive 
224 
copies/g 
OCT 10 
12.9 
330 
positive 
359 
copies/g 
positive 
433 
copies/g 
NOV 10 
12 
2400 
positive 
354 
copies/g 
positive 
100-500 
copies/g 
DEC 10 
5 
790 
positive 
2356 
copies/g 
positive 
6779 
copies/g 
FEB 11 
7.7 
310 
positive 
746 
copies/g 
positive 
1175 
copies/g 
MAR 11 
8.4 
230 
positive 
1133 
copies/g 
positive 
863 
copies/g 
APR 11 
10.5 
230 
positive 
146 
copies/g 
positive 
<100 
copies/g 
  
  
  
  
  
  
  
  
  
 
 
Site 34 
  
  
  
  
  
  
  
  
Water 
Month 
temperature 
E. coli 
Norovirus GI 
Norovirus GII 
MAY 09 
13 
<20 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
JUN 09 
16 
80 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
JUL 09 
15 
9200 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
AUG 09 
15 
490 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
SEP 09 
14 
230 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
OCT 09 
9 
230 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
NOV 09 
11 
1300 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
DEC 09 
8 
230 
not detected 
<40 
copies/g 
positive 
<100 
copies/g 
JAN 10 
2 
20 
not detected 
<40 
copies/g 
positive 
<100 
copies/g 
FEB 10 
2 
<20 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
MAR 10 
3 
<20 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
APR 10 
9 
20 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
MAY 10 
13 
<20 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
JUN 10 
17 
50 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
JUL 10 
16 
1700 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
AUG 10 
15 
20 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
SEP 10 
14 
170 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
OCT 10 
6 
130 
not detected 
<40 
copies/g 
positive 
<100 
copies/g 
NOV 10 
8 
1300 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
DEC 10 
2 
700 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
JAN 11 
6 
330 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
FEB 11 
5 
210 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
MAR 11 
6 
<20 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
APR 11 
12 
90 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
  
  
  
  
  
  
  
  
  
 
 
Site 35 
  
  
  
  
  
  
  
  
Water 
Month 
temperature 
E. coli 
Norovirus GI 
Norovirus GII 
MAY 09 
  
80 
not detected 
<40 
copies/g 
positive 
<100 
copies/g 
JUN 09 
13 
2400 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
JUL 09 
18 
2400 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
AUG 09 
14 
5400 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
SEP 09 
14 
2400 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
OCT 09 
14 
330 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
NOV 09 
12 
1300 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
DEC 09 
9 
170 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
JAN 10 
5 
70 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
FEB 10 
5 
<20 
positive 
1123 
copies/g 
not detected 
<40 
copies/g 
MAR 10 
8 
<20 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
APR 10 
5 
220 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
MAY 10 
5 
<20 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
JUN 10 
7 
130 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
JUL 10 
7 
1300 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
AUG 10 
10 
9200 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
SEP 10 
10 
220 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
OCT 10 
9 
790 
not detected 
<40 
copies/g 
positive 
<100 
copies/g 
NOV 10 
6 
130 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
DEC 10 
6 
20 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
JAN 11 
7 
20 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
FEB 11 
8 
<20 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
MAR 11 
7 
50 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
APR 11 
7 
20 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
  
  
  
  
  
  
  
  
  
 
 
Site 36 
  
  
  
  
  
  
  
  
Water 
Month 
temperature 
E. coli 
Norovirus GI 
Norovirus GII 
JUN 09 
13 
700 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
JUL 09 
13 
70 
no result 
  
no result 
  
 
 
AUG 09 
15 
<20 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
SEP 09 
14 
490 
no result 
  
no result 
  
 
 
OCT 09 
14 
<20 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
NOV 09 
11 
1300 
not detected 
<40 
copies/g 
positive 
<100 
copies/g 
DEC 09 
9 
80 
positive 
<100 
copies/g 
positive 
987 
copies/g 
JAN 10 
5 
<20 
positive 
<100 
copies/g 
positive 
1619 
copies/g 
FEB 10 
5 
80 
not detected 
<40 
copies/g 
positive 
589 
copies/g 
MAR 10 
8 
50 
not detected 
<40 
copies/g 
positive 
100-500 
copies/g 
APR 10 
5 
<20 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
MAY 10 
5 
130 
not detected 
<40 
copies/g 
positive 
<100 
copies/g 
JUN 10 
7 
80 
not detected 
<40 
copies/g 
positive 
<100 
copies/g 
JUL 10 
6 
790 
not detected 
<40 
copies/g 
positive 
<100 
copies/g 
AUG 10 
10 
130 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
SEP 10 
10 
20 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
OCT 10 
8 
<20 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
NOV 10 
7 
20 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
DEC 10 
6 
330 
not detected 
<40 
copies/g 
positive 
<100 
copies/g 
JAN 11 
6 
130 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
FEB 11 
8 
20 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
MAR 11 
7 
20 
not detected 
<40 
copies/g 
positive 
<100 
copies/g 
APR 11 
7 
<20 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
  
  
  
  
  
  
  
  
  
 
 
Site 37 
  
  
  
  
  
  
  
  
Water 
Month 
temperature 
E. coli 
Norovirus GI 
Norovirus GII 
MAY 09 
10 
490 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
JUN 09 
14 
2400 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
JUL 09 
16 
5400 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
AUG 09 
15 
1300 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
SEP 09 
13 
9200 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
OCT 09 
12 
790 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
JAN 10 
5 
80 
positive 
<100 
copies/g 
positive 
1549 
copies/g 
FEB 10 
7 
<20 
positive 
563 
copies/g 
positive 
2360 
copies/g 
MAR 10 
5 
80 
positive 
<100 
copies/g 
positive 
1186 
copies/g 
APR 10 
7 
20 
positive 
<100 
copies/g 
positive 
534 
copies/g 
MAY 10 
11 
20 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
JUN 10 
12 
50 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
JUL 10 
14 
1300 
not detected 
<40 
copies/g 
positive 
<100 
copies/g 
AUG 10 
14 
2400 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
SEP 10 
13 
170 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
OCT 10 
10 
130 
not detected 
<40 
copies/g 
positive 
<100 
copies/g 
NOV 10 
8 
790 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
JAN 11 
7 
50 
positive 
297 
copies/g 
positive 
564 
copies/g 
FEB 11 
5 
230 
positive 
160 
copies/g 
positive 
657 
copies/g 
MAR 11 
6 
50 
positive 
252 
copies/g 
positive 
462 
copies/g 
APR 11 
10 
170 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
  
  
  
  
  
  
  
  
  
 
 
Site 38 
  
  
  
  
  
  
  
  
Water 
Month 
temperature 
E. coli 
Norovirus GI 
Norovirus GII 
MAY 09 
10 
5400 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
JUN 09 
14 
330 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
JUL 09 
15 
490 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
AUG 09 
14 
50 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
SEP 09 
15 
230 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
OCT 09 
13 
330 
not detected 
<40 
copies/g 
positive 
<100 
copies/g 
NOV 09 
12 
330 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
DEC 09 
10 
<20 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
JAN 10 
7 
490 
no result 
  
no result 
  
 
 
FEB 10 
6.5 
330 
positive 
<100 
copies/g 
positive 
235 
copies/g 
MAR 10 
7 
230 
not detected 
<40 
copies/g 
positive 
100-500 
copies/g 
APR 10 
10 
<20 
not detected 
<40 
copies/g 
positive 
100-500 
copies/g 
MAY 10 
10 
<20 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
JUN 10 
11 
20 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
JUL 10 
14 
9200 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
AUG 10 
15 
170 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
SEP 10 
16 
700 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
OCT 10 
13 
330 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
NOV 10 
10 
20 
not detected 
<40 
copies/g 
positive 
1462 
copies/g 
DEC 10 
8 
50 
not detected 
<40 
copies/g 
positive 
249 
copies/g 
JAN 11 
6 
230 
positive 
<100 
copies/g 
positive 
1148 
copies/g 
FEB 11 
7 
<20 
positive 
<100 
copies/g 
positive 
106 
copies/g 
MAR 11 
9 
<20 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
APR 11 
11 
130 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
  
  
  
  
  
  
  
  
  
 
 
Site 39 
  
  
  
  
  
  
  
  
Water 
Month 
temperature 
E. coli 
Norovirus GI 
Norovirus GII 
MAY 09 
10 
80 
not detected 
<40 
copies/g 
positive 
<100 
copies/g 
JUN 09 
14 
790 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
JUL 09 
15 
330 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
AUG 09 
16 
1300 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
SEP 09 
14 
50 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
OCT 09 
12 
790 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
NOV 09 
11 
790 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
DEC 09 
8 
50 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
JAN 10 
7 
50 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
FEB 10 
6 
<20 
positive 
<100 
copies/g 
positive 
329 
copies/g 
MAR 10 
6 
20 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
APR 10 
9 
80 
not detected 
<40 
copies/g 
positive 
<100 
copies/g 
MAY 10 
10 
<20 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
JUN 10 
14 
<20 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
JUL 10 
14 
2200 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
AUG 10 
15 
790 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
SEP 10 
15 
<20 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
OCT 10 
13 
220 
not detected 
<40 
copies/g 
not detected 
<40 
copies/g 
NOV 10 
9 
70 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
DEC 10 
7 
20 
positive 
<100 
copies/g 
positive 
203 
copies/g 
JAN 11 
6 
50 
not detected 
<40 
copies/g 
positive 
<100 
copies/g 
FEB 11 
5 
20 
positive 
<100 
copies/g 
positive 
<100 
copies/g 
MAR 11 
9 
<20 
positive 
<100 
copies/g 
not detected 
<40 
copies/g 
APR 11 
9 
490 
positive 
533 
copies/g 
not detected 
<40 
copies/g 

 
 
Appendix 3: Statistical analysis 
 
Page 6: Oyster species comparison Two-way ANOVA: norovirus versus species, contamination  
 
Source         DF       SS       MS       F      P species         1   0.0614  0.06138    1.46  0.232 contamination   2  18.4199  9.20993  219.40  0.000 Interaction     2   0.1257  0.06287    1.50  0.233 Error          54   2.2668  0.04198 Total          59  20.8738 S = 0.2049   R-Sq = 89.14%   R-Sq(adj) = 88.13% Individual 95% CIs For Mean Based on Pooled StDev species      Mean  ----+---------+---------+---------+----- C.gigas   4.60887  (-----------*------------) O.edulis  4.67284            (------------*-----------) ----+---------+---------+---------+----- 4.560     4.620     4.680     4.740 Individual 95% CIs For Mean Based on Pooled StDev contamination     Mean  -----+---------+---------+---------+---- high           5.23487                                    (-*-) medium         4.78641                        (--*-) low            3.90129  (--*-) -----+---------+---------+---------+---- 4.00      4.40      4.80      5.20 
Page 10: GI vs GII Tabulated statistics: genogroup, result Using frequencies in C3 Rows: genogroup   Columns: result -     +   All GI     266   578   844 GII    377   467   844 All    643  1045  1688 Cell Contents:      Count Fisher's exact test: P-Value =  0.0000000 
 
 
Page 10: Summer vs winter prevalence Tabulated statistics: season, norovirus Using frequencies in C3 Rows: season   Columns: norovirus -    +  All summer    159  264  423 winter     42  379  421 All       201  643  844 Cell Contents:      Count Fisher's exact test: P-Value =  0.0000000 
Page 11: GI vs GII Wilcoxon Signed Rank Test: Diff Test of median = 0.000000 versus median not = 0.000000 N for   Wilcoxon         Estimated N   Test  Statistic      P     Median Diff  643    521    44434.0  0.000     -39.50 
Wilcoxon Signed Rank Test: Diff; <LOD = 0, <LOQ = 1 
Test of median = 0.000000 versus median not = 0.000000 N for   Wilcoxon         Estimated N   Test  Statistic      P     Median Diff  643    521    43352.0  0.000     -60.55 
Wilcoxon Signed Rank Test: Diff; <LOD = 40, <LOQ = 100 
 
Test of median = 0.000000 versus median not = 0.000000 N for   Wilcoxon         Estimated N   Test  Statistic      P     Median Diff  643    521    48094.0  0.000     -30.00 Page 11: Spearman's rank of GI vs GII Correlations: GIrank, GIIrank Pearson correlation of GIrank and GIIrank = 0.622 P-Value = 0.000 
 
 
Page 13: Yr1 vs Yr2 prevalence Tabulated statistics: year, norovirus Using frequencies in C3 Rows: year   Columns: norovirus -    +  All yr1     91  337  428 yr2    110  306  416 All    201  643  844 Cell Contents:      Count Fisher's exact test: P-Value =  0.0895321 Page 13: Yr1 vs Yr2 Kruskal-Wallis Test: norovirus versus year Kruskal-Wallis Test on norovirus year       N  Median  Ave Rank      Z yr1      428   100.0     417.1  -0.65 yr2      416   100.0     428.1   0.65 Overall  844             422.5 H = 0.43  DF = 1  P = 0.513 H = 0.44  DF = 1  P = 0.506  (adjusted for ties) Page14: Between regions comparison Kruskal-Wallis Test: norovirus versus region Kruskal-Wallis Test on norovirus region                               N  Median  Ave Rank      Z England - East Coast                12  226.30      22.8   1.00 England - South Coast               13  194.60      23.9   1.52 England - West Coast, Wales and NI   8  118.74      18.5  -0.42 Scotland                             6   81.92       8.0  -2.80 Overall                             39              20.0 H = 9.02  DF = 3  P = 0.029 
 
 
Kruskal-Wallis: All Pairwise Comparisons  
---------------------------------------- Comparisons:                     6 Family Alpha:                    0.2 Bonferroni Individual Alpha:     0.033 Bonferroni Z-value (2-sided):    2.128 ---------------------------------------- Standardized Absolute Mean Rank Differences |Rbar(i)-Rbar(j)| / Stdev Rows:    Group i = 1,...,n Columns: Group j = 1,...,n 1. Table of Z-values England - East Coast              0.00000        *        *  * England - South Coast             0.25701  0.00000        *  * England - West Coast, Wales & NI  0.81665  1.05848  0.00000  * Scotland                          2.58732  2.82961  1.70520  0 2. Table of P-values England - East Coast              1.00000        *        *  * England - South Coast             0.79717  1.00000        *  * England - West Coast, Wales & NI  0.41413  0.28984  1.00000  * Scotland                          0.00967  0.00466  0.08816  1 ---------------------------------------------------------- Sign Confidence Intervals controlled at a family error rate of 0.2 Desired Confidence:    86.761 Sign confidence interval for median Confidence Achieved    Interval N  Median  Confidence  Lower  Upper  Position norovirus_England - East Coast   12   226.3      0.8540   90.0  393.3         4 0.8676   89.2  399.9       NLI 0.9614   73.3  537.3         3 norovirus_England - South Coast  13   194.6      0.7332  173.9  200.5         5 0.8676  166.0  205.6       NLI 0.9077  160.6  209.0         4 norovirus_England - West Coast,   8   118.7      0.7109  112.8  175.3         3 0.8676  104.8  186.7       NLI 0.9297   95.3  200.3         2 norovirus_Scotland                6    81.9      0.7813   52.0   95.7         2 0.8676   51.8  106.4       NLI 0.9688   50.5  169.2         1 
Kruskal-Wallis: Conclusions The following groups showed significant differences: Groups                                     Z vs. Critical value       P-value England - South Coast vs. Scotland         2.82961 >= 2.128           0.0047 England - East Coast vs. Scotland          2.58732 >= 2.128           0.0097 


Page15: Between species comparison Kruskal-Wallis Test: norovirus versus species Kruskal-Wallis Test on norovirus species    N  Median  Ave Rank      Z C.gigas   28   164.9      19.9  -0.12 O.edulis  11   173.9      20.4   0.12 Overall   39              20.0 H = 0.02  DF = 1  P = 0.901 Page 16: Between classifications comparison Kruskal-Wallis Test: norovirus versus classification  
 
Kruskal-Wallis Test on norovirus classification   N   Median  Ave Rank      Z A                6    81.92       8.7  -2.65 B               31   179.55      21.5   1.67 C                2  1208.33      30.0   1.27 Overall         39               20.0 H = 8.04  DF = 2  P = 0.018 * NOTE * One or more small samples Page16: Between classifications comparison - post hoc analysis Kruskal-Wallis: All Pairwise Comparisons  
---------------------------------------- Comparisons:                     3 Family Alpha:                    0.2 Bonferroni Individual Alpha:     0.067 Bonferroni Z-value (2-sided):    1.834 ---------------------------------------- Standardized Absolute Mean Rank Differences |Rbar(i)-Rbar(j)| / Stdev Rows:    Group i = 1,...,n Columns: Group j = 1,...,n 1. Table of Z-values A  0.00000        *  * B  2.53313  0.00000  * C  2.29157  1.01603  0 2. Table of P-values A  1.00000        *  * B  0.01130  1.00000  * C  0.02193  0.30961  1 ---------------------------------------------------------- 
 
 
Sign Confidence Intervals controlled at a family error rate of 0.2 Desired Confidence:    80.529 Sign confidence interval for median Confidence Achieved    Interval N  Median  Confidence  Lower  Upper  Position norovirus_1_A   6    81.9      0.7813   52.5   95.7         2 0.8053   52.5   98.0       NLI 0.9688   52.0  175.3         1 norovirus_1_B  31   179.5      0.7190  138.3  197.1        13 0.8053  133.5  198.9       NLI 0.8504  129.5  200.3        12 norovirus_1_C   2    1208      0.5000    174   2243         1 The highest attainable confidence has been achieved. 

Kruskal-Wallis: Conclusions The following groups showed significant differences: Groups          Z vs. Critical value       P-value A vs. B         2.53313 >= 1.834           0.0113 A vs. C         2.29157 >= 1.834           0.0219 
Page 17: Spearman's rank norovirus vs. *E. coli* sample-by-sample Correlations: ranknorovirus, rankE.coli  
 
Pearson correlation of ranknorovirus and rankE.coli = 0.195 P-Value = 0.000 
Page 18: Spearman's rank norovirus vs. *E. coli* **site-by-site** 
Correlations: ranknorovirus, rankE.coli 
 
Pearson correlation of ranknorovirus and rankE.coli = 0.453 P-Value = 0.004 
Page 18: Spearman's rank norovirus vs. *E. coli* **site-by-site, winter** 
Correlations: ranknorovirus, rankE.coli Pearson correlation of ranknorovirus and rankE.coli = 0.676 P-Value = 0.000 
Page 18: Spearman's rank norovirus in oysters vs. HPA lab reports Correlations: rankoyster, rankHPA 
Pearson correlation of rankoyster and rankHPA = 0.761 P-Value = 0.000 
 

## Page 20: Spearman'S Rank Norovirus In Oysters Vs. Uk Average Air Temperatures Correlations: Rankoyster, Ranktemp Pearson Correlation Of Rankoyster And Ranktemp = -0.877 P-Value = 0.000 Page 20: Spearman'S Rank Norovirus In Oysters Vs. Water Temperatures (Individual Sites) Site 1 Correlations: Ranktemp, Ranknoro Pearson Correlation Of Ranktemp And Ranknoro = -0.797 P-Value = 0.000 Site 2 Correlations: Ranktemp, Ranknoro Pearson Correlation Of Ranktemp And Ranknoro = -0.783 P-Value = 0.000 Site 3 Correlations: Ranktemp, Ranknoro Pearson Correlation Of Ranktemp And Ranknoro = -0.528 P-Value = 0.014 Site 4 Correlations: Ranktemp, Ranknoro Pearson Correlation Of Ranktemp And Ranknoro = -0.879 P-Value = 0.000 Site 7 Correlations: Ranktemp, Ranknoro Pearson Correlation Of Ranktemp And Ranknoro = -0.766 P-Value = 0.001 Site 8 Correlations: Ranktemp, Ranknoro Pearson Correlation Of Ranktemp And Ranknoro = -0.676 P-Value = 0.001 Site 9 Correlations: Ranktemp, Ranknoro Pearson Correlation Of Ranktemp And Ranknoro = -0.596 P-Value = 0.003 Site 10 Correlations: Ranktemp, Ranknoro Pearson Correlation Of Ranktemp And Ranknoro = -0.603 P-Value = 0.002 Site 11 Correlations: Ranktemp, Ranknoro Pearson Correlation Of Ranktemp And Ranknoro = -0.865 P-Value = 0.000 Site 12 Correlations: Ranktemp, Ranknoro Pearson Correlation Of Ranktemp And Ranknoro = -0.755 P-Value = 0.000 Site 13 Correlations: Ranktemp, Ranknoro Pearson Correlation Of Ranktemp And Ranknoro = -0.747 P-Value = 0.003 Site 14 Correlations: Ranktemp, Ranknoro Pearson Correlation Of Ranktemp And Ranknoro = -0.433 P-Value = 0.160 Site 15 Correlations: Ranktemp, Ranknoro Pearson Correlation Of Ranktemp And Ranknoro = -0.737 P-Value = 0.000 Site 16 Correlations: Ranktemp, Ranknoro Pearson Correlation Of Ranktemp And Ranknoro = -0.573 P-Value = 0.005 Site 17 Correlations: Ranktemp, Ranknoro Pearson Correlation Of Ranktemp And Ranknoro = -0.870 P-Value = 0.000

 

## Site 18 Correlations: Ranktemp, Ranknoro Pearson Correlation Of Ranktemp And Ranknoro = -0.587 P-Value = 0.027 Site 20 Correlations: Ranktemp, Ranknoro Pearson Correlation Of Ranktemp And Ranknoro = -0.737 P-Value = 0.004 Site 21 Correlations: Ranktemp, Ranknoro Pearson Correlation Of Ranktemp And Ranknoro = -0.359 P-Value = 0.208 Site 22 Correlations: Ranktemp, Ranknoro Pearson Correlation Of Ranktemp And Ranknoro = -0.862 P-Value = 0.000 Site 23 Correlations: Ranktemp, Ranknoro Pearson Correlation Of Ranktemp And Ranknoro = -0.783 P-Value = 0.001 Site 24 Correlations: Ranktemp, Ranknoro Pearson Correlation Of Ranktemp And Ranknoro = 0.002 P-Value = 0.992 Site 25 Correlations: Ranktemp, Ranknoro Pearson Correlation Of Ranktemp And Ranknoro = -0.704 P-Value = 0.001 Site 26 Correlations: Ranktemp, Ranknoro Pearson Correlation Of Ranktemp And Ranknoro = -0.690 P-Value = 0.000

 

## Site 27 Correlations: Ranktemp, Ranknoro Pearson Correlation Of Ranktemp And Ranknoro = -0.549 P-Value = 0.008 Site 28 Correlations: Ranktemp, Ranknoro Pearson Correlation Of Ranktemp And Ranknoro = -0.407 P-Value = 0.060 Site 29 Correlations: Ranktemp, Ranknoro Pearson Correlation Of Ranktemp And Ranknoro = -0.618 P-Value = 0.003 Site 30 Correlations: Ranktemp, Ranknoro Pearson Correlation Of Ranktemp And Ranknoro = -0.330 P-Value = 0.124 Site 31 Correlations: Ranktemp, Ranknoro Pearson Correlation Of Ranktemp And Ranknoro = -0.615 P-Value = 0.005 Site 32 Correlations: Ranktemp, Ranknoro Pearson Correlation Of Ranktemp And Ranknoro = -0.242 P-Value = 0.333 Site 33 Correlations: Ranktemp, Ranknoro Pearson Correlation Of Ranktemp And Ranknoro = -0.832 P-Value = 0.000 Site 34 Correlations: Ranktemp, Ranknoro Pearson Correlation Of Ranktemp And Ranknoro = -0.373 P-Value = 0.080

 

## Site 35 Correlations: Ranktemp, Ranknoro Pearson Correlation Of Ranktemp And Ranknoro = 0.013 P-Value = 0.954 Site 36 Correlations: Ranktemp, Ranknoro Pearson Correlation Of Ranktemp And Ranknoro = -0.142 P-Value = 0.539 Site 37 Correlations: Ranktemp, Ranknoro Pearson Correlation Of Ranktemp And Ranknoro = -0.754 P-Value = 0.000 Site 38 Correlations: Ranktemp, Ranknoro Pearson Correlation Of Ranktemp And Ranknoro = -0.460 P-Value = 0.027 Site 39 Correlations: Ranktemp, Ranknoro Pearson Correlation Of Ranktemp And Ranknoro = -0.746 P-Value = 0.000 Page 20: Spearman'S Rank Norovirus Vs. Risk Score Correlations: Rankrisk, Ranknorovirus Pearson Correlation Of Rankrisk And Ranknorovirus = 0.546 P-Value = 0.001 Page 21: Spearman'S Rank Norovirus Vs. Sampling Risk Score Correlations: Ranksampling Risk Score, Ranknorovirus Pearson Correlation Of Ranksampling Risk Score And Ranknorovirus = 0.645 P-Value = 0.000