United States

Department of

Agriculture

Animal and Plant

Health Inspection

Service

Veterinary Services

Epidemiologic and Other Analyses of 

HPAI/LPAI Affected Poultry Flocks

June 26, 2017 Report
Epidemiologic and Other Analyses of HPAI/LPAI Affected Poultry Flocks June 26, 2017

Suggested bibliographic citation for this report: 

USDA-APHIS (2017). Epidemiologic and other analyses of HPAI/LPAI affected poultry flocks:

June 26, 2017 Report. USDA:APHIS:VS:STAS:Center for Epidemiology and Animal Health.

Fort Collins, CO. June 2017. Doc #391.0317 V2. 39 pgs.

For more information, contact: 

Bruce A. Wagner, PhD

Director, Center for Epidemiology and Animal Health

USDA:APHIS:Veterinary Services

Science, Technology, and Analysis Services

Center for Epidemiology and Animal Health

2150 Centre Avenue, Bldg. B-2E7, Fort Collins, CO, 80526-8117

Phone (970) 494-7256 | Mobile (970) 237-0857 | Fax (970) 494-7228

Email: Bruce.A.Wagner@aphis.usda.gov

Web: http://www.aphis.usda.gov/animal-health/ceah

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(Version 2; June 26, 2017)

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Document #391.0317 V2 (June 26, 2017)
Epidemiologic and Other Analyses of HPAI/LPAI Affected Poultry Flocks June 26, 2017

USDA APHIS VS i

Contents

I. Executive Summary .....................................................................................................................1

II. Introduction ................................................................................................................................2

Description of Outbreak .................................................................................................................................2

III. Epidemiologic Studies to Investigate H7N9 Virus in Poultry in Tennessee, Alabama, Kentucky, 

and Georgia.................................................................................................................................5

A. Case Series...............................................................................................................................................5

Commercial Breeder Farms.........................................................................................................................5

Backyard Flocks ...........................................................................................................................................7

B. Egg Production and Mortality Data .........................................................................................................8

C. Expert Elicitation Study..........................................................................................................................12

D. Route of Lateral Spread between HPAI-Infected Premises...................................................................14

E. References:............................................................................................................................................14

IV. Phylogenetic Analysis and Diagnostics........................................................................................16

A. North American H7N9 HPAI and LPAI from poultry (AM H7N9 2017) ..................................................16

B. Comparison to Other Viruses/Lineages.................................................................................................19

C. Public Health Aspects............................................................................................................................20

D. Diagnostics and Characterization for Influenza A Viruses.....................................................................20

General Information..................................................................................................................................20

V. Waterfowl Surveillance..............................................................................................................22

VI. Wildlife On-Farm Sampling ........................................................................................................25

A. Sampling for Avian Influenza Virus in Synanthropic Wildlife at an Infected Premises..........................25

Objective ...................................................................................................................................................25

B. Procedures.............................................................................................................................................25

Sampling Procedures.................................................................................................................................25

Laboratory Procedures..............................................................................................................................25

C. Test Results............................................................................................................................................26

Wildlife Sampling Results..........................................................................................................................26

Laboratory Results.....................................................................................................................................27

Wildlife Observational Results ..................................................................................................................27

D. Summary................................................................................................................................................28

E. References.............................................................................................................................................28

VII. Acknowledgements ...................................................................................................................29

Appendix A: Case Series Questionnaire..............................................................................................30

Appendix B: Expert Elicitation Questionnaire .....................................................................................31
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List of Figures and Tables

Figure 1. Counties with confirmed findings of HPAI or LPAI H7 or H7N9 since March 1, 2017 and their 

locations relative to major chicken and turkey-producing States in the United States.................................3

Figure 2. Timeline of detections of HPAI and LPAI infected flocks by flock type and pathogenicity of virus 

detected. First detections in each State are highlighted................................................................................4

Figure 3. Egg production (eggs per hen) for LPAI case farms from August 2016 through March 2017 by 

individual barn (colored lines). Most recent ELISA and PCR test results are shown for each farm. ..............9

Figure 4. Hen mortality (percent daily mortality) for LPAI case farms from August 2016 to March 2017 by 

individual barn (colored lines). Most recent ELISA and PCR test results are shown for each farm. ............10

Figure 5. Egg production (egg per hen) and hen mortality (daily percent mortality) for four non-infected 

barns from December 2016 through March 2017 by individual barn (colored lines)..................................11

Figure 6. Wind-related weather conditions for Lincoln County, TN during the first two weeks of March.........15

Figure 7. Nearest wild bird precursor viruses contributing to the AM H7N9 gene constellation.......................17

Figure 8. Schematic phylogenetic tree of the HA1 nucleotide sequences of H7 AIVs. .......................................18

Figure 9. Distribution and flow of related gene segments in wild bird viruses that contribute to the AM 

H7N9 2017....................................................................................................................................................19

Figure 10. The four primary North American waterfowl flyways........................................................................22

Figure 11. Timeline of virus detections in wild birds (A) and locations of influenza A detections by IAV-M 

PCR from wild bird surveillance from July 2015 through March 2017 (B) ...................................................24

Table 1. Location, production type, pathogenicity, and confirmation date of flocks infected during the 

H7N9 HPAI/LPAI outbreak..............................................................................................................................4

Table 2. Characteristics of poultry farms testing positive for avian influenza H7N9............................................6

Table 3. Number of wildlife species sampled at a farm with chickens infected with AM H7N9 IAV, 

Tennessee, 2017, by species sampled..........................................................................................................26

Table 4. Number of samples collected from birds and mammals at a farm with chickens infected with AM 

H7N9 IAV in Tennessee, 2017, by sample type............................................................................................27
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I. EXECUTIVE SUMMARY

A combined outbreak of highly pathogenic avian influenza (HPAI) and low pathogenic avian 

influenza (LPAI) started in early March 2017. The outbreak was first suspected by an increase in 

mortality on a commercial breeder farm in Tennessee and was confirmed as H7N9 highly 

pathogenic avian influenza (HPAI) of North American wild bird lineage (AM H7N9 HPAI) via 

laboratory testing. After initial efforts to control the disease, a series of epidemiologic, genetic,

and wildlife investigations were started. This is a report of the findings available to-date, and 

these analyses are intended to assist in understanding disease introduction and transmission 

pathways. These studies were undertaken collaboratively with the poultry industry, State

agriculture personnel, and the Animal and Plant Health Inspection Service. 

The outbreak area lies primarily in south central Tennessee and northern Alabama, but cases 

have occurred in southern Kentucky and western Georgia. This area is bounded by dense areas 

of poultry production, including broiler, table-egg layer, and turkey operations.

Sampling and testing of wildlife was implemented near a commercial premises infected with

AM H7N9 Influenza A virus (IAV). Initial results have not confirmed the presence of H7N9 IAV 

from wild bird samples; however, limited evidence suggests that one or more animals sampled 

may have been previously exposed to an IAV.

Genetic analyses determined that all H7N9 viruses detected from this event are of North 

American wild bird lineage, and the HPAI and LPAI viruses are highly similar across all eight 

genes, excluding the multi-basic amino acid insertion at the cleavage site in the HPAI virus. 

Initial genetic and epidemiologic evidence suggest the possibility of more than a single 

introduction with limited lateral transmission. These viruses were most likely introduced in 

late February based on available barn-level egg production, mortality, and testing information.

H7 detections have occurred during summer, fall, and winter and throughout the Mississippi 

and Atlantic Flyways. Annually, H7 detections tend to peak in early winter. This pattern may 

have contributed to the timing of this outbreak in the southeastern United States.

The six commercial AM H7N9 LPAI farms involved five different integrated poultry complexes 

suggesting unique sources of feed, pullets, males, egg transport trucks, and crews for most of 

the cases. Potential routes of lateral spread between farms, related to potential concerns such 

as the biosecurity of egg pickup, trucks, visitors, equipment and disposal activities, did not 

appear to be risk factors during this outbreak. However, factors such as the presence of rodents 

and other wild mammals and waterfowl near barns, the condition of the housing, and breaches 

in biosecurity protocols were identified as risk factors that could bring viruses into the barns

from the environment. The fact that backyard operations have also been impacted adds 

credence to the theory that this outbreak was governed in large part by exposure to 

environmental sources of virus.

Broiler flocks located in the area were unaffected during this outbreak. Results from the expert 

elicitation highlighted differences in housing type, age of birds, and length of the production 

cycle, which could help explain why broiler flocks were not infected.
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II. INTRODUCTION

In response to the H7N9 avian influenza outbreaks in commercial and backyard poultry in AL, 

GA, KY, and TN, USDA-APHIS-Veterinary Services, APHIS Wildlife Services, and the affected 

states have initiated epidemiologic, genetic, and wildlife investigations. These investigations

will help provide a better understanding of factors associated with avian influenza virus 

transmission and its introduction into poultry flocks.

These investigations include the following: 

• A field-based study of cases using data collected through site visits and interviews with 

farm personnel 

• Analysis of barn-level egg production and mortality records

• An expert elicitation study

• Virus phylogenetic analyses

• Analysis of waterfowl surveillance

• On-farm sampling of wildlife.

This report includes the results from these investigations, in an effort to provide producers, 

industry, and other stakeholders with current epidemiologic information. 

Description of Outbreak

On March 2, 2017, an increase in mortality was noted on a commercial broiler breeder farm in 

Lincoln County, TN. The United States Department of Agriculture (USDA) National Veterinary 

Services Laboratories (NVSL) confirmed H7 highly pathogenic avian influenza (HPAI) of North 

American wild bird lineage on March 4, 2017 and N9 on March 6, 2017 (AM H7N9 HPAI). 

Surveillance in the area was immediately initiated to determine the status of other farms. A 

second commercial broiler breeder farm was confirmed positive for AM H7N9 HPAI on March 

15, 2017. The second HPAI-positive farm also was located in Lincoln County, TN. In addition to 

the two HPAI-positive farms, an additional six commercial broiler breeder operations and six 

backyard flocks were found positive with H7 and H7N9 low pathogenic avian influenza North 

American wild bird lineage. The eight commercial broiler breeder farms affected in this 

outbreak were distributed across six companies and four States (Figure 1, Table 1). The 

timeline of detections is shown in Figure 2 with dates of confirmation shown in Table 1. In total, 

approximately 252,000 birds died from disease or were depopulated to control the outbreak. 
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Figure 1. Counties with confirmed findings of HPAI or LPAI H7 or H7N9 since March 1, 2017 and their 

locations relative to major chicken and turkey-producing States in the United States. 

The top four chicken-producing and turkey-producing States are highlighted based on the National 

Agricultural Statistics Service’s Poultry – Production and Value 2015 Summary report.1

 

1 http://usda.mannlib.cornell.edu/usda/nass/PoulProdVa//2010s/2016/PoulProdVa-04-28-2016.pdf
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Figure 2. Timeline of detections of HPAI and LPAI infected flocks by flock type and pathogenicity of virus 

detected. First detections in each State are highlighted.

Table 1. Location, production type, pathogenicity, and confirmation date of flocks infected during the H7N9 

HPAI/LPAI outbreak.

State County Production Type Pathogenicity Confirmation Date

Tennessee Lincoln Commercial Broiler Breeder HPAI 3/4/2017

Tennessee Giles Commercial Broiler Breeder LPAI 3/8/2017

Alabama Madison Backyard Producer LPAI 3/10/2017

Alabama Lauderdale Commercial Broiler Breeder LPAI 3/14/2017

Alabama Jackson Backyard Producer Guinea 

Fowl LPAI 3/15/2017

Tennessee Lincoln Commercial Broiler Breeder HPAI 3/15/2017

Tennessee Lincoln Backyard Producer LPAI 3/15/2017

Tennessee Lincoln Backyard Producer LPAI 3/15/2017

Alabama Pickens Commercial Broiler Breeder LPAI 3/16/2017

Alabama Madison Backyard Producer LPAI 3/17/2017

Kentucky Christian Commercial Broiler Breeder LPAI 3/17/2017

Alabama Cullman Commercial Broiler Breeder LPAI 3/21/2017

Kentucky Christian Backyard Producer LPAI 3/21/2017

Georgia Chattooga Commercial Broiler Breeder LPAI 3/25/2017
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III. EPIDEMIOLOGIC STUDIES TO INVESTIGATE H7N9 VIRUS IN POULTRY IN 

TENNESSEE, ALABAMA, KENTUCKY, AND GEORGIA

A. Case Series

USDA-APHIS conducted a case-series study among H7N9 affected commercial broiler-breeder 

poultry operations. The purpose of this study was to generate hypotheses for potential risk 

factors for infection with H7N9 avian influenza virus. Additionally, study respondents provided

mortality data; egg production data; a copy of biosecurity manuals, if available; and a farm 

diagram highlighting the locations of key areas, such as ponds. Questions focused on the 3 

weeks prior to the earliest indication of infection (clinical signs, drop in production, or positive 

test) (Appendix A: Case Series Questionnaire).

Commercial Breeder Farms

Completed case-series questionnaires were available from 8 commercial broiler breeder farms 

(6 multiplier farms and 2 primary breeders), which represented 2 HPAI-confirmed farms and 6 

LPAI-confirmed or presumptive farms. Results of the questionnaires are summarized in Table 2. 

Results 

• Four of the eight farms reported respiratory signs in poultry prior to the positive AI test. 

• Ponds (5 farms) and streams (5 farms) were the most common types of water bodies 

located within 350 yards of the farms. Wild waterfowl were not observed outside the 

barns on any of the farms and other wild birds were rarely observed. Chickens did not 

have outdoor access on any farms.

• Workers did not work on other farms or own poultry, and were required to stay off the 

farm if they had exposure to poultry. A clean/dirty line was established on all eight

farms. The barns’ hard surface entry way was cleaned and disinfected on three of the

farms. Only one farm used different personnel for different barns. Footwear was not 

scrubbed on any of the farms although change of shoes was required on five farms. 

• Feed trucks, egg removal trucks, egg flats/racks/pallets were commonly shared with 

other farms. Feed, egg, and company personnel vehicles entered the farm and most 

drove up near the barns. Vehicles were not washed at every entry or exit to the farms

during the 3-week risk period (6 farms). All 8 farms had visits from their company 

service person during the 21-day risk period and the company service person entered 

the barn on 7 of the farms.

• The most common method of dead bird disposal was composting (6 farms), and the 

carcasses were covered with soil or manure usually after 2 or more days. The dead bird 

disposal area was located within 40 yards of the barn on 6 farms.
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Summary 

Although the results demonstrate common practices across case farms, without information on 

control farms, we cannot say that these are necessarily risk factors. Therefore, these results 

need to be interpreted cautiously. However, some of the common practices have been shown to 

be risk factors in other studies. These results should be considered in context with the findings 

of the expert elicitation study, which explored the implementation of biosecurity protocols on 

these farms in comparison to unaffected farms (Section C). 

Table 2. Characteristics of poultry farms testing positive for avian influenza H7N9

Characteristic Level n Comments

Farm level factors:

Bird type • Multiplier

• Primary breeder

5

2

Clinical signs 4 4 farms reported respiratory 

signs prior to positive test, 3 

farms reported decreased 

egg production

Outdoor access • no 8/8

Water body within 350 yds • Pond

• stream

5/8

5/7

Other poultry • No 8/8

Water source • municipal 7/8

Wild birds on the farm outside 

of barn

• Water fowl

• Small perching birds

0/8

6/8

1 dead buzzard

Wild birds in the barns 0/8

Workers • Establish clean/dirty line

• Shower

• Change clothes

• Change shoes

• Scrub footwear

• Different personnel for 

different barns

• Work on other farms/own 

poultry

• Required to stay off farm 

after exposure to poultry

8/8

2/8

4/8

5/7

0/5

1/7

0/8

8/8

Most 72 hours

Visitors • Company service person

• Feed delivery personnel

• Egg truck personnel

8/8

6/8

6/8

Vehicles shared with other 

farms

• Feed truck

• Egg removal

• Stored outside uncovered

8/8

8/8

6/6
Epidemiologic and Other Analyses of HPAI/LPAI Affected Poultry Flocks June 26, 2017

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Characteristic Level n Comments

Equipment shared with other 

farms

• Egg racks/pallets

• Egg flats

6/7

6/7

Vehicles enter the farm • Feed delivery

• Company personnel

• Egg truck

8/8

6/8

8/8

Most reported these vehicles 

drive up near the barns

Vehicles washed prior to or 

upon leaving farm

2/8

Dead bird disposal method • Composting

• Incineration

• Rendering

6

1

1

Covered with soil or manure 

every 2 or more days

Wild birds, mammals or 

domestic animals seen around 

the dead bird disposal area

2/8

Barn level factors:

Health concern 2 Respiratory illness

Ventilation type • Curtain

• Tunnel

• Ceiling/eaves

2

5

1

Fans located at end of barn 7/8

Hard surface entry cleaned and 

disinfected

3/8

Service room for entry 6/8

Footbath varies

Last full cleanout • Prior to this flock 8/8

Wild birds (live or dead) in barn 0/8

Dead bird disposal area within 

40 yds

6/8

Visitors entering the barn • Company service person 7/8 No other visitor type 

frequently reported

Backyard Flocks

Questionnaires were completed for five AI-positive backyard operations. Three of these 

operations were identified by area surveillance and two by routine flea market testing. None of 

the operations were aware of a health concern during the 3-week risk period prior to testing 

positive.

Results/Summary: 

All 5 operations had chickens; 4 operations had ducks and other poultry. Poultry had outdoor 

access on all 5 operations. Flock size for respondents ranged from 15 to 340 birds. Dead birds 

were disposed of by burial (3 operations) or landfill (1 operation). Footbaths were not used by 

any of the operations. The nearest body of water was within 100 yards of the poultry barn for 3 
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operations. Water bodies within 350 yards of the premises included ponds (2 flocks) and 

wetlands or swamp (2 flocks). Wild birds were seen on all 5 operations including wild 

waterfowl on 2 operations. Wild birds were seen in the barns on all 5 premises. All 5 operations 

had dogs on the premises. Additional notes on the surveys indicated no known connection 

could be identified to commercial poultry or other backyard flocks. Also, some flocks had free 

access to the entire property while others were enclosed in pens. The occurrences of exposure 

to risk factors and the lack of connection to other commercial or backyard flocks seems to 

indicate that lateral transmission was not an important route of infection for these flocks.

B. Egg Production and Mortality Data

Egg production and mortality data were obtained for five case farms (farms that tested positive 

for AI via PCR) and four barns from two non-infected farms. The non-infected farms came from 

within the control zone in Tennessee. Dates for the last negative serologic test were available 

for four of the case farms and dates of a positive serologic test for one farm; however, we were 

unable to link the test results back to an individual barn on these farms. Figure 3 shows eggs 

per hen per day from September through March for each barn for each LPAI case farm. Figure 4

shows mortality (percent hens that died) for these same barns for the same time period. Figure 

5 shows egg production and mortality for the control barns during the same time period.

Barn-level egg production patterns were similar on case and non-infected farms in that there 

was a period of approximately 3 to 4 weeks after placement that egg production rapidly 

increased, then plateaued and gradually decreased over several months.
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Figure 3. Egg production (eggs per hen) for LPAI case farms from August 2016 through March 2017 by 

individual barn (colored lines). Most recent ELISA and PCR test results are shown for each farm.
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Figure 4. Hen mortality (percent daily mortality) for LPAI case farms from August 2016 to March 2017 by 

individual barn (colored lines). Most recent ELISA and PCR test results are shown for each farm.
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Figure 5. Egg production (egg per hen) and hen mortality (daily percent mortality) for four non-infected

barns from December 2016 through March 2017 by individual barn (colored lines).

Results/Summary 

Unlike the uninfected barns, all five case farms had drops in egg production for a short period of 

time in specific barns. A production drop for the two HPAI farms (data not shown) occurred 

several months in single barns before testing positive for AI. These farms had negative serologic 

tests long after these egg production drops had resolved, and therefore, it is likely that a 

problem unrelated to AI was responsible for these early drops in production. Both of the HPAI 

farms experienced a sudden marked spike in mortality immediately prior to testing positive,

with mortality rates reaching 1-4%. There was an approximately 2-week gap between the 

mortality events on the two HPAI farms. Farms C and D had drops in egg production that 

occurred after a previous negative serologic test for AI and prior to a positive PCR test. These 

drops in egg production coincide with a slight increase in mortality. Farm E also had a notable 

drop in egg production with a coinciding increase in mortality prior to testing positive for AI.

(Information regarding the last negative test was not available for Farm E.)

Given standard incubation times for AI viruses in poultry, these findings suggest that the virus 

was likely introduced into these flocks in late February except for the second HPAI infected 

farm, which appears to be due to lateral transmission in mid-March. It is possible that these less 

severe drops in production and increased mortality on farms C, D, and E may be related to 

infection with a LPAI virus. However, the impacts of LPAI virus introduction are subtle and 
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difficult to distinguish from regular variability in egg production or mortality, as shown in the 

data from the uninfected barns.

C. Expert Elicitation Study

An expert opinion elicitation was conducted to rapidly characterize risk factors and possible 

routes of exposure for commercial premises involved in the 2017 AM H7N9 HPAI/LPAI 

outbreak in the four State region of Tennessee, Alabama, Kentucky and Georgia. The expert 

panel included 6 company veterinarians, 1 laboratory clinician, and 1 government poultry 

health specialist—all with first-hand knowledge of the outbreak. The elicitation involved a 

series of questions about known (real) cases and controls, as well as a hypothetical component 

in which experts envisioned the likely distribution of risk factors among farms involved in an 

imagined outbreak that was similar to, but larger than the real outbreak. Survey questions and 

introductions are available in Appendix B. The inquiry method was scripted to estimate 

likelihood ratios (LR, measures of association akin to odds ratios) for risk factors of potential 

influence in this outbreak.

In individual interviews, experts responded to a series of risk factor questions about the case 

broiler breeder farm(s) with which they were most familiar. They also responded to the same 

series of questions about a control (non-affected) broiler breeder farm for each case. Controls 

were selected by the experts under the direction that each should match a case site in 

production type, timing, and region and their level of familiarity. The identity of neither cases 

nor controls were provided to the analysts; so, in order to avoid site duplication, only the six 

company veterinarians’ (one per company) responses were used in the matched (real) casecontrol component. For the case control segment, the goal was to allow a rapid characterization 

of risk factors among known sites in lieu of a formal but more intensive epidemiologic field 

study. All eight experts participated in the hypothetical scenario. Here, experts were asked to 

assign the probable rates of occurrence of risk factors among affected versus unaffected farms 

in an imagined outbreak of the same etiology, timing, and type as the existing outbreak, but 

scaled up in size. The goal of this segment was to encourage structured speculation on key 

factors most relevant to prevention and control of AM H7N9 IAV and similar viruses in this 

industry.

Results/Summary 

Results suggest a limited role for farm-to-farm (lateral) transmission, and a likely greater role 

for environmental sources of exposure, in this outbreak. While lateral spread was implicated 

between two HPAI sites based on genetic homology between the isolates, close geographic 

proximity, and company ties between the two farms, direct farm-to-farm transfer routes among 

the AM H7N9 LPAI commercial broiler breeder sites were not apparent. The six commercial 

LPAI farms involved five different integrated poultry complexes suggesting unique sources of 

feed, pullets, males, egg transport trucks, and crews for most of the cases. Furthermore, factors 

representing potential for lateral spread were evenly balanced in abundance between cases and 

controls. Thus, questions about the biosecurity of egg pickup, trucks, visitors, equipment and 

disposal activities, held no predictive strength in this analysis. In contrast, several 
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environmental risk factors, present in a preponderance of cases over controls, did show 

predictive strength. These included disturbance by mesopredators or rodents, enclosure 

defects that could jeopardize pest exclusion or events that might result in local attraction of 

these animals. Density of poultry operations in the area was also predictive. Interestingly, 

proximity to large congregations of waterfowl was cited in only one case, and wetland 

environments were no more prevalent in cases than controls.

The hypothetical scenario similarly pointed to environmental factors such as rodents, 

waterfowl (rather than mesopredators), and the condition of the housing. However, in the 

hypothetical scenario, biosecurity of equipment, workers and visitors entering the chicken 

houses, as well as biosecurity of vehicles entering the farm, ranked high in predictive strength.

Egg carts rolled from truck to barn across outdoor concrete pads, workroom doors held open 

for cooling that might allow an alternative to the formal entrance with foot bath, improper use 

(e.g., without first removing organics) and maintenance of foot baths, or inadequate worker 

instruction in biosecurity, were potential gaps cited. The focus of expert discussion was on 

exposure to virus present in the surrounding environment, though many of the same 

mitigations would also reduce opportunities for lateral spread. The relevance of biosecurity 

measures ranking high in the hypothetical component, but not in the case control component, 

emphasizes concerns that breaches in standard protocol could be the avenue for virus 

introduction onto these farms. The fact that backyard operations have also been impacted adds 

credence to the theory that this outbreak was governed in large part by exposure to 

environmental sources of virus.

Finally, experts were asked for their hypotheses explaining the exclusion of broilers and table 

egg layers in this outbreak. For table egg layers, the answer most often cited was their lack of 

abundance in the affected region. For broilers, responses included their younger age, shorter 

production cycle, fewer opportunities for testing prior to market, and possible reduced

susceptibility to the virus. Experts observed that most broiler farms’ barns are solid wall sided 

and temperature controlled, while many broiler breeder farms’ barns are curtain sided and lack 

the need for tight temperature control. Broiler operations sustain less foot traffic than broiler 

breeders which require frequent worker entry for egg, feed, and animal oversight. Additionally, 

broiler breeder barns include roosting/feeding sections raised up on slats above ground, which

could potentially offer safe harborage underneath for rodents or other pests. Thus, the two 

systems vary in conditions that could impact virus exposure and persistence, as well as host 

susceptibility and detection.

The small sample size and subjective nature of the data limit the conclusive strength of this 

study. However, results can help bridge decision support until further research is conducted.

Further exploration might consider the role of mesopredators and rodents, the importance of 

housing type and condition (on virus exposure, bird susceptibility, or viral persistence), 

conditions or periods predictive of greatest risk of introduction from the environment, and 

design of enhanced biosecurity protocols to balance periods of elevated risk. Finally, experts 
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noted that adjusting routine testing to include PCR, in addition to serology, could improve speed 

of detection of HPAI/LPAI viruses during high-risk periods. 

D. Route of Lateral Spread between HPAI-Infected Premises

Epidemiologic and genomic evidence (Section IV) suggest there was farm-to-farm (lateral) 

spread of virus between the two HPAI-positive commercial broiler breeder farms. 

Epidemiologic investigation of the movements of eggs and workers for the two farms did not 

clearly identify the linkage that could have resulted in viral introduction to the second farm.

Individuals involved with the outbreak hypothesized that the virus was spread farm-to-farm via 

wind, although other methods of spread were also possible. In order to explore this hypothesis, 

wind conditions were obtained for the period of time between the two HPAI detections. Both 

HPAI-positive farms were part of the same poultry company and the first HPAI-infected farm 

was located approximately one mile southeast of the second HPAI-infected farm.

Results/Summary 

Wind direction during the period of interest was predominately blowing from the south, which 

supports the wind spread hypothesis (Figure 6). Anecdotal evidence obtained during the expert 

opinion elicitation also supports this hypothesis. An individual on the second farm reported the 

wind was blowing from the direction of the first farm during the disposal period, and that they 

were able to smell odors from disposal activities. Additionally, the first barn positive on the 

second farm was the barn closest to the first farm. Of special note, there was a broiler farm 

between these two farms that did not become infected, which is inconsistent with the wind 

spread hypothesis. Possible reasons for this lack of infection of the broiler farm that was in 

proximity to two AM H7N9 HPAI infected farms are discussed in the Expert Opinion Elicitation 

(Section C). There are differences in housing and ventilation structure that could result in a 

broiler farm not receiving the same amount of exposure to wind-related materials. 

Although these results are not conclusive, detection of AIV in air has been documented 

(Torremorell, 2016) and standard operating procedures should be followed when managing an 

HPAI-infected flock in order to reduce opportunities for wind-related spread. 

E. References:

Montserrat Torremorell, Carmen Alonso, Peter R. Davies, Peter C. Raynor, Devi Patnayak, Mia 

Torchetti, and Brian McCluskey (2016). Investigation into the Airborne Dissemination of 

H5N2 Highly Pathogenic Avian Influenza Virus during the 2015 Spring Outbreaks in the 

Midwestern United States. Avian Diseases: September 2016, Vol. 60, No. 3, pp. 637-643.
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Figure 6. Wind-related weather conditions for Lincoln County, TN during the first two 

weeks of March
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IV. PHYLOGENETIC ANALYSIS AND DIAGNOSTICS

A. North American H7N9 HPAI and LPAI from poultry (AM H7N9 2017)

This section describes AM H7N9 HPAI and LPAI from poultry confirmed by the National

Veterinary Services Laboratories (NVSL) during March 2017.2 These viruses are different from 

the Asian H7N9 virus from China that emerged in 2013 and continues to impact poultry and 

humans in Asia.

Two broiler breeder flocks were confirmed with AM H7N9 HPAI within 10 days of one another 

in Lincoln County, Tennessee. The insertion at the cleavage site responsible for the highly 

pathogenic phenotype of the AM H7N9 HPAI is likely derived from chicken host 28S ribosomal 

RNA, suggesting that AM H7N9 LPAI virus was introduced to the first flock and mutated to the 

highly pathogenic form during virus replication in poultry (Figure 7). Similar insertion events of 

chicken ribosomal RNA have contributed to the emergence of HPAI in poultry from LPAI from 

this and other poultry-related H7 IAV. 

During the time between the two HPAI detections, AM H7N9 LPAI was confirmed in a broiler 

breeder flock in Giles County, Tennessee. Additional H7 (and N9, where confirmed) LPAI and 

presumptive LPAI were detected through zone and routine surveillance and extended into AL, 

KY, and GA, respectively.

The second flock affected by HPAI was in the control zone and therefore undergoing weekly 

testing by real-time reverse transcription polymerase reaction (rRT-PCR) for permitting 

purposes. Just prior to the onset of clinical signs, one of 18 samples (6 pooled samples per 

house) collected 3/13/2017 and tested at the NAHLN lab had a high Ct by IAV-M PCR, 

suggesting the presence of a low amount of viral RNA (the subtype tests were negative).3 While 

the high Ct was not repeatable at NVSL, HPAI virus was recovered from this sample during a 

second passage. Clinical signs were reported in the flock on 3/14/2017, and samples collected 

from sick and dead birds in 3/14/2017 confirmed the presence of HPAI in the same house as 

the high Ct sample from 3/13/2017. The high similarity between the HPAI viruses from the first 

and second site, the timing of detection, and the available epidemiological data, indicates the 

potential for secondary spread of HPAI from the first site to the second site. 

 

2 Virus availability announcements: https://www.aphis.usda.gov/aphis/ourfocus/animalhealth/veterinarybiologics/biologics-regulations-and-guidance/ct_vb_notices

3 Samples with a high Ct by IAV-M, which is the primary surveillance tool, may be negative by the subtype tests that 

target a different gene.
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The AM H7N9 HPAI and LPAI viruses are highly similar across the entire genome (Figure 7; 

excluding the multibasic amino acid insertion at the cleavage site responsible for the mutation 

to HPAI) and are of North American wild bird lineage based upon the full genome sequence4

(North American Cluster III viruses; blue box in Figure 8). 5

North American H7N9 LPAI has previously been detected in wild birds in the U.S., and a closely 

related H7N9 LPAI virus (Figure 7; >99.1-99.8% similar across all eight gene segments) was 

recovered from a Wildlife Services Wild Bird Surveillance sample. This sample was collected 

from a blue-winged teal in Wyoming as part of a live-bird banding effort in September 2016. 

Other highly similar gene segments have been identified from North American H7N9, N3, N7, 

and H11 LPAI in wild birds from 2015-2017 (Figure 9). 

 

4 Genbank IDs: AM H7N9 HPAI KY818808-818815 and KY818832-818839; AM H7N9 LPAI KY818816-818823

5 Xu Y, Bailey E, Spackman E, et al. 2016. Contemporary H7 Avian-Origin Influenza A Viruses from North America 

(Scientific Reports, 6: 20688) 

Figure 7. Nearest wild bird precursor viruses contributing to the AM H7N9 gene constellation. 

Two wild bird viruses were collected from blue-winged teal: one in Saskatchewan, Canada during 

August 2016 (BWT/SK/2016; blue bars representing the eight gene segments), and the other in 

Wyoming during September 2016 (BWT/WY/2016; blue and yellow bars – NOTE: the pictogram with 

the yellow bars is a theoretical precursor virus based upon phylogenetic analysis). The BWT/WY/2016 

and the virus from chickens in TN (CK/TN/2017) are greater than 99% similar across the entire 

genome. 

Courtesy of D.H. Lee, USDA ARS Southeast Poultry Research Laboratory and Y. Berhane, National 

Centre for Foreign Animal Diseases - Avian Diseases Unit, Canada. 
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This virus is NOT the same as the Asian H7N9 virus that emerged in China during 2013 and 

continues to impact poultry and humans. All AM H7N9 2017 viruses detected from this event 

are of North American wild bird lineage.

Further phylogenetic analyses of the full genome from HPAI viruses from two sites in TN, and 

LPAI viruses from one commercial flock each in TN and AL, and two AL backyard flocks was 

conducted. In summary: 

1) The AM H7N9 HPAI and LPAI viruses are highly similar across the entire genome (excluding

the multibasic amino acid insertion at the cleavage site responsible for the mutation to 

HPAI) and are of North American wild bird lineage based upon the full genome sequence 

(Figure 7);

2) The insertion at the cleavage site responsible for the highly pathogenic phenotype of the AM 

H7N9 HPAI is likely derived from chicken host 28S ribosomal RNA; 

3) The virus from the Wyoming blue-winged teal likely represents a precursor to the AM H7N9 

2017 viruses found in poultry (Figure 7 and Figure 8); and

4) Molecular, epidemiologic, and serologic (antibody) data suggest the AM H7N9 virus 

circulated in the area undetected in poultry prior to the initial HPAI detection.

5) Molecular and epidemiologic support exists for a) secondary spread from the first HPAI site 

to the second, and b) more than one independent introduction of AM H7N9 LPAI, for 

example the available data show that LPAI/HPAI viruses from TN appear to have a common

source and cluster separately from the AL viruses. 

Figure 8. Schematic phylogenetic tree of the HA1 nucleotide 

sequences of H7 AIVs.

The tree was constructed based on the phylogeny inferred 

by using the maximum-likelihood method. Boxes represent

the three major genetic clusters; the Eurasian lineage (EU) 

is represented by the large black triangle. Am = North 

American lineage. 

The AM H7N9 2017 viruses are located in Cluster III. 

Courtesy of Xi-Feng Wan et al, Department of Basic 

Sciences, College of Veterinary Medicine, Mississippi State 

University
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NOTE: The outcomes of phylogenetic analysis should be interpreted in context of all available 

virus and epidemiologic information and should not be used to infer transmission. Studies to 

determine virus infectivity and transmission are underway at the USDA ARS Southeast Poultry 

Research Laboratory.

B. Comparison to Other Viruses/Lineages

Before the current events in 2017, the most recent H7 HPAI event occurred in 2016, affecting 

turkeys in Indiana. Both the AM H7N9 2017 and Indiana H7N8 2016 events were identified when 

an LPAI virus mutated to HPAI and samples were collected in response to clinical signs observed in 

the birds. The distribution of cases and the presence of antibody-positive flocks for the AM H7N9 

suggest that detection occurred later during the course of infection as compared to the H7N8 2016, 

where infection was detected shortly after virus introduction based upon active virus shedding in 

both HPAI and LPAI affected barns. The H7N8 2016 and AM H7N9 2017 viruses are somewhat 

related across five (PB2, PB1, HA, NP, MP) of eight genes but are clearly different in the other three 

genes (PA, NA, NS).

Figure 9. Distribution and flow of related gene segments in wild bird viruses that contribute to the AM 

H7N9 2017.

The colors correspond to different gene segments; the maps show the temporal and geographic 

distribution of the detection of related gene segments in other wild bird viruses. 

Courtesy of Lei Li et al, Department of Basic Sciences, College of Veterinary Medicine, Mississippi State 

University
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There have been other reports of North American H7N9, most recently in 2009 and 2011. 

Compared to the AM H7N9 2017, both the H7N9 2011 and 2009 viruses show some relatedness 

across three genes (2011: HA, NA, MP; 2009: PB1, NA, MP), but are different across the other 

five genes. This finding was expected as IAV reassorts frequently in wild birds; Figure 9

demonstrates the detection of related gene segments in wild bird viruses over time that 

contribute to the AM H7N9 2017 constellation. Additionally, the H7 of the AM H7N9 2017 

belongs to a different lineage compared to the H7N3 HPAI from Mexico reported in the public 

database. 

C. Public Health Aspects

To date, no cases of AM H7N9 2017 virus infection have been reported in humans. Efforts to 

monitor the health of response workers and on-farm personnel continue.

The virus and sequence have been shared with CDC (refer to this link) for analysis which 

indicated that the viruses to date lack key amino acid substitutions associated with human-like 

receptor binding or substitutions in the polymerase or other internal genes associated with 

increased virulence and transmission in mammals; no known markers of neuraminidase 

inhibitor (Oseltamivir) resistance have been identified. 

D. Diagnostics and Characterization for Influenza A Viruses

The NVSL rapidly shares genetic and biological materials in collaboration with the Southeast 

Poultry Research Laboratory, the Influenza Division of the Centers for Disease Control and 

Prevention, Wildlife Services, as well as other key partners. Consensus data from whole genome 

sequencing are used to monitor the virus evolution and assess the risk to veterinary and public 

health based upon the presence/absence of specific amino acid substitutions or protein motifs.

Analysis of sequence data includes phylogeny of all eight segments and determination of amino 

acid substitutions across the HA1 protein. Genetic data are also used to confirm that diagnostic 

assays are fit for purpose. In silico analysis confirmed high identity between the AM H7N9 virus 

sequences and the primers and probes used for the IAV and H7 diagnostic rRT-PCR tests.

General Information

Avian influenza subtypes H5 and H7 are reportable worldwide because of their potential for 

mutation to high pathogenicity during replication in poultry. The presence of basic amino acids 

at the cleavage site contribute to the mutation from low to high pathogenicity. Mechanisms by 

which H5/H7 mutate from LPAI to HPAI include the gradual accumulation of basic amino acids 

(AA), insertion of repeated basic AA, and insertion of non-homologous genetic material (only 

reported for H7 viruses). 

Molecular diagnostic tests for influenza A virus (IAV) are used across the U.S. National Animal 

Health Laboratory Network (NAHLN). The most sensitive and specific tool for influenza A 

detection is the Type A-specific rRT-PCR, which targets at least the matrix gene (IAV-M); this is 

the primary surveillance tool used and provides a semi-quantitative result. The NAHLN tests 
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samples first by the IAV-M test and further by the NAHLN H5 and H7 tests where IAV is 

detected. 

All poultry samples with a non-negative test result for IAV (serology or PCR) are forwarded to 

NVSL for confirmatory testing. The NVSL uses Sanger sequencing protocols to generate partial 

HA/NA sequence directly from the sample for subtype and pathotype determination, when 

sufficient viral RNA is present. Whole genome sequencing is conducted on all isolated viruses, 

and select viruses are further characterized by pathotype assay in specific pathogen-free 

chickens. 

Confirmation of the virus involves determination of the HA and NA subtype, and the pathotype 

(LPAI vs HPAI). Until NVSL results are available (usually less than 24 hours from sample receipt 

for H5 and H7), the HA-subtype remains ‘presumptive.’ The pathotype is also ‘presumptive’

based upon the clinical presentation of the flock compared to the USDA HPAI case definition. 

NVSL results ‘confirm’ the HA and NA subtype (by molecular and/or antibody testing) and the 

pathotype (LPAI or HPAI by molecular testing); however, where virus is not recovered and 

sequence cannot be obtained directly from the sample, the pathotype will remain ‘presumptive.’
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V. WATERFOWL SURVEILLANCE

Waterfowl are natural reservoir hosts for influenza A viruses (IAV; subtypes H1-H16), but not 

usually HPAI. Influenza A viruses in wild birds tend to circulate seasonally within migratory 

flyways, and subtype prevalence can wax/wane in multiyear cycles. Areas where birds from 

different flyways congregate provide opportunities for viruses to mix across flyways.

Waterfowl migration in North America generally consists of north-south seasonal movements 

between breeding grounds and wintering areas. There are four major flyways in North America 

(Figure 10). These flyways are broadly defined corridors where the migratory paths of many 

species of interest tend to converge and are associated with major topographical features in 

North America, which also tend to be aligned along a north-south axis. The four North American 

flyways have areas of overlap and convergence, particularly at the north and south ends.

Flyway boundaries are defined administratively, and are not biologically fixed or sharply 

defined. 

Figure 10. The four primary North American waterfowl flyways
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North American flyways represent the predominant pathways of migratory bird movements 

within broad geographic areas. Many migratory bird species use specific flyways during spring 

and fall; however, many species migrate across flyways. The Pacific Flyway is most likely the 

area of introduction for the HPAI viruses detected in Canada and the western United States in 

December 2014. 

The U.S. National Surveillance Plan for Highly Pathogenic Avian Influenza in Wild Birds was 

implemented in 2015 to maximize our ability to detect IAV in wild waterfowl. Surveillance helps 

to: 1) understand how IAV is distributed in the United States, 2) detect the spread of IAV to new

areas of concern, 3) monitor wild dabbling duck populations for introductions of novel viruses,

and 4) estimate the apparent prevalence of IAVs of concern (e.g., Eurasian lineage H5 and H7). 

The surveillance plan targets areas with extensive mixing of wild bird populations and a history 

of IAV detection.

Since July 1, 2015, over 80,000 wild waterfowl have been sampled and tested by rRT-PCR for 

IAV. Overall, the wild waterfowl surveillance has resulted in detection of about 500 H7 viruses 

across all four flyways. Of these detections, 215 were from the Atlantic and Mississippi Flyways. 

H7 detections have occurred during summer, fall, and winter and throughout the Mississippi 

and Atlantic Flyways (Figure 11). Annually, H7 detections tend to peak in early winter. This 

pattern may have contributed to the timing of the recent outbreak in the southeastern United 

States.

The H7 graph is based on viruses recovered at NVSL from H7 presumptive samples forwarded 

by NAHLN laboratories. 

• Wild bird surveillance testing follows the NAHLN testing algorithm: samples are first 

tested by a Type A-specific test (IAV-M) and further tested by the H5/H7 subtype tests 

in which viral RNA is detected. H5 and H7 samples are forwarded to NVSL, as genetic 

sequencing is the most reliable test for determining virus subtype(s) in wild birds. 

• Wild birds are often exposed to IAV and mount an antibody response that can kill the 

virus, leading to unsuccessful virus isolations.

The graph for influenza A detections is based upon NAHLN laboratory detections using the Type 

A-specific test (IAV-M), regardless of the virus recovery status.
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Figure 11. Timeline of virus detections in wild birds (A) and locations of influenza A detections by IAV-M PCR 

from wild bird surveillance from July 2015 through March 2017 (B)
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VI. WILDLIFE ON-FARM SAMPLING

A. Sampling for Avian Influenza Virus in Synanthropic Wildlife at an Infected Premises

Objective

To evaluate the potential of synanthropic wildlife associated with commercial chicken (Gallus 

gallus domesticus) flocks becoming exposed or infected with North American (AM) H7N9 IAV, 

we sampled peridomestic birds and mammals on a single farm where chickens were infected 

with AM H7N9 IAV. The timeframe for sampling additional farms for wildlife did not allow 

collection on other affected premises.

Wildlife sampling at the premises was initiated within 6 six days after virus shedding was 

confirmed in poultry by the NVSL. The flock was depopulated 4 to 5 days (dependent on barn 

number) before sampling was initiated. We sampled throughout the farm, but focused in and 

around the barn with confirmed AM H7N9 IAV infected chickens prior to depopulation.

B. Procedures

Sampling Procedures 

Wild birds and wild mammals were captured on the infected farm, primarily around farm 

structures, with an emphasis (e.g., more traps and nets) on sampling at the barn on this 

property in which chickens were infected with AM H7N9 IAV. Wild birds were captured using 

mist nets and baited funnel traps. Wild mammals were trapped using baited collapsible 

Sherman traps and baited Tomahawk traps. To test for evidence of AM H7N9 IAV infection, 

captured animals were sampled via swab collection, nasal washes (mammals), and tissues 

(from some animals). Evidence of prior exposures was investigated by testing serum for the 

presence of antibodies. 

From birds, we collected oral swabs, cloacal swabs, and blood samples (when possible). From 

mammals, we collected oral swabs, nasal swabs/washes, and blood samples. We also collected 

lung-tissue samples from targeted species (e.g., house mice and house sparrows). Swabs, 

washes, and tissue samples were placed in 1-3mL of viral transport media and stored chilled. 

Blood was collected into serum separator tubes, allowed to clot, and centrifuged. Field 

personnel shipped samples overnight on ice packs to testing laboratories during the week or 

stored them in a refrigerator and drove them to laboratories during weekends.

Laboratory Procedures 

All samples were screened for influenza A virus (IAV) matrix (M) gene RNA via real-time 

reverse transcriptase polymerase chain reaction (rRT-PCR). The Veterinary Diagnostic 

Laboratory at Colorado State University conducted IAV-M rRT-PCR testing of avian oral and 

cloacal swabs, while the National Wildlife Research Center Virology Laboratory conducted all 

other IAV-M testing. Samples with Ct>0 by IAV-M were submitted to the NVSL for confirmatory 

testing. Detections by the IAV-M PCR were tested for presence of the H5 and H7 subtypes, and 
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genetic sequencing when possible; virus isolation in embryonated chicken eggs was conducted 

in parallel. All serum samples with sufficient volume and from selected species were screened 

for antibodies to an IAV using the IDEXX AI Multi-S Screen Ab test, which is a multispecies 

blocking enzyme linked immunosorbent assay (ELISA) targeting an epitope of the 

nucleoprotein. Samples were also forwarded to NVSL for hemagglutinin inhibition (HI) testing. 

C. Test Results

Wildlife Sampling Results

We sampled 118 individual animals over a 4-day period in March 2017. In all, 61 mammals 

represented by four species (mice and mesocarnivores) and 57 birds represented by 19 species 

(primarily passerines) were sampled (Table 3). The most common mammal captured was the 

house mouse (Mus musculus), and the most common bird captured was the American robin 

(Turdus migratorius). Overall, we collected 109 serum samples, 118 oral swabs, 57 cloacal 

swabs, 61 nasal swab/wash samples, and 57 lung-tissue samples (Table 4).

Table 3. Number of wildlife species sampled at a farm with chickens infected with AM H7N9 IAV, Tennessee, 

2017, by species sampled.

Sampled species Scientific Name Number Sampled

House mouse Mus musculus 53

Virginia opossum Didelphis virginiana 4

White-footed mouse Peromyscus leucopus 3

Raccoon Procyon lotor 1

Total Mammals: 61

American robin Turdus migratorius 14

White-throated sparrow Zonotrichia albicollis 8

Savannah sparrow Passerculus sandwichensis 6

Northern cardinal Cardinalis cardinalis 5

Song sparrow Melospiza melodia 4

Northern mockingbird Mimus polyglottos 3

Eastern phoebe Sayornis phoebe 3

House finch Haemorhous mexicans 3

House sparrow Passer domesticus 1

Eastern towhee Pipilo erythrophthalmus 1

Blue jay Cyanocitta cristata 1

Vesper sparrow Pooecetes gramineus 1

Dark-eyed junco Junco hyemalis 1

Brown thrasher Toxostoma rufum 1

Carolina wren Thryothorus ludovicianus 1

Yellow-rumped warbler Setophaga coronata 1

Carolina chickadee Poecile carolinensis 1

Eastern bluebird Sialia sialis 1

Mourning dove Zenaida macroua 1

Total Birds: 57

Total Combined: 118
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Table 4. Number of samples collected from birds and mammals at a farm with chickens infected with AM 

H7N9 IAV in Tennessee, 2017, by sample type.

Sample type

Total number 

collected

Number Collected 

from Birds

Number Collected 

from Mammals

Serum 109 49 60

Oral Swab 118 57 61

Cloacal Swab 57 57 ---- a

Nasal Swab/Wash 61 ----a 61

Lung Tissue 57 1 56 aSamples not collected.

Laboratory Results

All avian swab samples were screened by IAV-M rRT-PCR. A very low level of matrix gene RNA 

was detected in one (1) of 57 combined oral/cloacal swab samples (represented by a high 

Ct/Cq value of 39.45). This sample, collected from a savannah sparrow, tested negative by H5 

and H7 assays at the original testing laboratory, which was not unexpected as the low level of 

viral RNA detected approaches the limit of detection for the assay. The sample was forwarded 

to NVSL where the high Ct was not repeatable (also not unexpected). Virus isolation was not 

successful on the sample, which was not unexpected. Of interest, the bird was captured adjacent 

to the barn (approximately 5 meters) that housed AM H7N9 HPAI infected chickens prior to 

depopulation.

ELISAs were conducted on avian serum samples with sufficient volume and on select 

mammalian samples. Two of the 42 samples screened showed potential evidence of antibodies 

reactive to influenza A virus. These results were associated with an American robin (average 

sample-to-negative [S/N] ratio of 0.525) and a Virginia opossum (Average S/N ratio of 0.665). 

The S/N ratio of the American robin is consistent with that of one from an American robin 

sampled in Iowa during 2015, which was confirmed positive for antibodies to icA-H5 by HI 

(Shriner et al. 2016). To our knowledge, this ELISA has not been previously validated with 

Virginia opossum sera. The S/N ratio of the suspect positive Virginia opossum (0.665) was 

moderately lower than the average S/N ratio of the three other opossum serum samples 

(0.820). Serum samples were forwarded to the NVSL for HI tests. Serum samples that were not 

prescreened with ELISA tests (all mesocarnivores except the Virginia opossum mentioned 

above) and with sufficient volume were assayed with an HI for H7 antibodies. None tested 

positive by HI. In addition, 13 avian samples, primarily those with insufficient volumes for 

ELISA tests and the single American robin with an S/N ratio of 0.525, tested negative for H7 

antibodies by HI. Because the remaining avian serum samples were prescreened by ELISA tests, 

additional HIs were not conducted.

Wildlife Observational Results

A relatively high rodent burden was noted on the infected farm. Of interest, the barns farthest 

from the infected barn had the highest densities of mice, many of which were observed 

primarily utilizing exterior walls of the barns for cover.
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Overall, the farm had very small populations (< 10 per species) of invasive birds (house 

sparrows [Passer domesticus] and European starlings [Sturnus vulgaris]) during the sampling 

period. This small population may be indicative of the lack of spilled feed associated with grain 

hoppers at this premises.

A pond located on the farm’s property, likely attracts some wildlife species for water resources. 

Although we did not directly observe any ducks or geese using this pond during the wildlife 

sampling period, we did observe wood ducks (Aix sponsa) and Canada geese (Branta 

canadensis) flying over the infected premises during the evening on two sequential days. In 

addition, that same morning a great blue heron (Ardea herodias) was observed foraging in the 

pond.

Anecdotal evidence of other wildlife on the property (those not captured) included potential 

signs of skunks (Mephitis sp.), nine-banded armadillos (Dasypus novemcinctus), and coyotes 

(Canis latrans). Regarding the latter, the property owner reported recently observing coyotes

on his farm, and the wildlife epidemiology team observed one coyote within 1 mile of the 

infected premises during the sampling period. Direct observations of groundhogs (Marmota 

monax) on the east side of the farm were also made on multiple days. Some additional avian 

species observed on the perimeter edge of the farm but not captured included cedar waxwings 

(Bombycilla cedrorum), an unidentified tanager (Piranga sp.), white-crowned sparrows 

(Zonotrichia leucophrys), and red-winged blackbirds (Agelaius phoeniceus).

D. Summary 

It is clear from both wildlife captures and observations that a diversity of wildlife used this 

facility for various reasons. Initial results did not confirm the presence of AM H7N9 IAV from 

wild bird or mammal samples; however, limited evidence suggests that one or more animals 

sampled may have been previously exposed to a different IAV.

E. References

Shriner, S.A., J.J. Root, M.W. Lutman, J.M. Kloft, K.K. VanDalen, H.J. Sullivan, T.S. White, M.P. 

Milleson, J.L. Hairston, S.C. Chandler, P.C. Wolf, C.T. Turnage, B.J. McCluskey, A.L. Vincent, 

M.K. Torchetti, T. Gidlewski, and T.J. DeLiberto. 2016. Surveillance for highly pathogenic H5 

avian influenza virus in synanthropic wildlife associated with poultry farms during an acute 

outbreak. Scientific Reports 6:36237.
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VII. ACKNOWLEDGEMENTS

We greatly appreciate the cooperation and support of the poultry industry and farm owners for 

allowing us access to their properties, for providing information on their biosecurity and 

production practices, and for their full cooperation with this investigation. 

We also appreciate the poultry health professionals who participated in the expert elicitation 

study and the valuable time they shared with our team, as well as the many partners who 

assisted with this study while serving in the incident command for this outbreak. 

This report would not have been possible without a large group of researchers, epidemiologists, 

laboratory staff, and data scientists who participated in the various analyses and drafting and 

review of this report. We appreciate their dedication and professionalism in providing the best 

information possible to help producers reduce the risk of IAV introduction into their 

operations. 
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APPENDIX A: CASE SERIES QUESTIONNAIRE

HPAI/LPAI

Questionnaire

Broilers

INSTRUCTIONS

State and local poultry organizations and the U.S. Department of Agriculture APHIS (USDA–

APHIS) are collecting data as part of the avian influenza investigation efforts to identify factors 

that may contribute to transmission of avian influenza virus to poultry.

We are asking you to fill out this survey, which includes questions about things done daily on the 

farm, facility and premises condition, deliveries to the farm, and ill birds. We ask about a 3-week 

(21-day) period on the farm starting on a particular date that we will provide. It might be 

difficult to remember back that far, so please use a pocket calendar or other agenda manager 

and any feed and other delivery records that might be available to you.

Term Case definition Control definition

Premises Farm location with flocks confirmed to 

be avian influenza infected by NVSL, 

including all barns and buildings, even 

if not all barns and buildings contain 

infected birds.

Farm location with no infected birds in any 

barn or building, in close proximity (less 

than 10 miles) to the case farm. (If case 

farm is a broiler breeder, select a noninfected broiler breeder as the control.)

Barn Barn or building that houses avian 

influenza-infected birds.

On control premises, a barn or building that 

does not house any avian influenza-infected 

birds.

The complete survey is available on request.

HPAI case control 

questionnaire_broilers

National Animal Health 

Monitoring System

2150 Centre Ave., Bldg B

Fort Collins, CO 80526

Form Approved

OMB Number 0579-0376

Approval Expires: 9/30/2017

According to the Paperwork Reduction Act of 1995, an agency may not conduct or sponsor, and a person is not required 

to respond to a collection of information unless it displays a valid OMB control number. The valid OMB control number for 

this information collection is 0579-0376. The time required to complete this information collection is estimated to average 

1 hour per response, including the time to review instructions, search existing data resources, gather the data needed, 

and complete and review the information collected

NAHMS-347

SEP 2015

Animal and Plant 

Health Inspection

Service

Veterinary Services
Epidemiologic and Other Analyses of HPAI/LPAI Affected Poultry Flocks June 26, 2017

USDA APHIS VS 31

APPENDIX B: EXPERT ELICITATION QUESTIONNAIRE

2017 LPAI/HPAI Expert Opinion Elicitation

Introduction

Thank you for agreeing to participate in this expert opinion elicitation to rapidly characterize risk and 

protective mechanisms involved in the 2017 outbreak of H7N9 in Tennessee, Alabama, Georgia, and 

Kentucky. Our goal is to capture, through your opinions, data similar to what are more typically obtained 

through case control studies. This approach is much faster, allows experts to balance their responses 

with prior knowledge and context, and removes any references to specific sites. As a subjective process, 

it can also be swayed by bias, but, to improve objectivity, we ask for counts of events (rather than 

probabilities), and ground your counts first in real observations. We also stage a forum in which group 

results can be challenged and discussed, after which experts will have a chance to individually revise 

their responses. Individual responses will remain confidential; group median scores and variability will 

be reported. If it looks like a publication may result, we’ll ask you to review the draft manuscript and 

consider co-authorship, if interested.

Below are a series of questions about plausible routes of HPAI/LPAI introduction onto a farm. We ask 

that you to respond to these questions in two parts. Part one will reference one or two case (HPAI/LPAI 

positive) farms and one or two control (HPAI/LPAI negative) farms that you know well. Part two will 

revolve around a set of hypothetical farms. Focus on the 6-8 week period before detection in the case 

farms, and the same period for their controls. We’ll walk you through both processes.
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Part One: Real Cases and Controls

Select (without naming) one or more H7N9 broiler breeder case farms (HPAI or LPAI) with which you are 

most familiar. Call these Case A, Case B, etc. Select (again without naming) two broiler breeder control 

farm for each case. Call these Control A1, Control A2, Control B1, Control B2 ,etc. Each control farm 

should match its case farm in production type (primary versus multiplier breeder), timing of 

production, size of operations, and within same control area if possible. Otherwise, it should simply be 

a farm with which you are most familiar. Please answer the following questions about each of these 

cases and controls. 

1. Spiking Male Source Responses

Did the farm test spiking male source populations by a protocol geared to detect a 

recent introduction of LPAI/HPAI? Case Controls

a. Yes, including PCR in the pre-movement test, targeting sick or dead birds for 

sampling, and routinely including PCR to investigate clinical signs or drops in 

production

b. No, using ACIA or serology or only sampling healthy birds for testing, or using 

only serology to investigate clinical signs or drops in production

2. Pullet Source

Did the farm source pullets from populations first tested by a protocol geared to detect

a recent introduction of LPAI/HPAI? Case Controls

a. Yes, including PCR in the pre-movement test, targeting sick or dead birds for 

sampling, and routinely including PCR to investigate clinical signs or drops in 

production

b. No, using ACIA or serology or only sampling healthy birds for testing, or using 

only serology to investigate clinical signs or drops in production

3. Wind

Was the farm situated downwind (and within a mile or so) of a source of infective 

material (e.g., positive farm, disposal location or depopulation/disposal traffic)? Case Controls

a. Yes

b. No

4. Habitat Disruption 

Did the farm experience conditions that may attract local rodent/wildlife (e.g., sale of a 

neighboring farm, disruption of perimeter habitats, or local feed/waste spills)? Case Controls

a. Yes

b. No

5. Integrated Poultry Complex

Was the farm part of a poultry complex with other farm(s) subsequently found to be 

LPAI/HPAI positive? Case Controls

a. Yes, the complex included another infected farm

b. No, the complex does not include other infected farms, but periodically had 

to externally source feed or pullets 

c. No, the complex did not include other infected farms, and did not have to 

externally source feed or pullets
Epidemiologic and Other Analyses of HPAI/LPAI Affected Poultry Flocks June 26, 2017

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6. Vehicle Biosecurity

Which best describes biosecurity measures used for vehicles involved in bird delivery, 

egg pickup or bird processing or disposal? Case Controls

a. Minimal biosecurity precautions 

b. Moderate biosecurity precautions (e.g., interior and exterior of vehicles, 

including tires, are cleaned and disinfected daily)

c. Strong biosecurity precautions (e.g., interior and exterior of vehicles, 

including tires, are cleaned and disinfected between farms)

7. Operation Equipment Biosecurity

Which best describes biosecurity used for equipment shared between farms and in 

contact with birds or eggs (e.g., farm racks, egg flats, carts, egg buggies, bird crates)? Case Controls

a. Minimal biosecurity precautions 

b. Strong biosecurity precautions (e.g., cleaned and disinfected before entry to 

farm)

8. Farm Equipment Biosecurity (tillers, skid steers, etc)

Which best describes biosecurity for farm equipment used in chicken houses? Case Controls

a. Minimal biosecurity precautions 

b. Moderate biosecurity precautions (e.g., cleaned and disinfected before entry 

to houses; if sharing between farms washed after use)

c. Strong biosecurity precautions (e.g., cleaned and disinfected before entry to 

houses, no sharing between farms) 

9. Shared Disposal Routes

Did the farm share mortality disposal destinations (renderers, compost piles, burial 

pits, etc) with other farms subsequently found to be LPAI/HPAI positive? Case Controls

a. Yes, shared with a farm subsequently found LPAI/HPAI positive

b. Yes, shared with other farms, but unsure which ones

c. Either (1) shared but not with farms subsequently found LPAI/HPAI positive, 

or (2) not shared with other farms

10. Catch Crews and Processing

Did the farm process chicken houses at different times (not including depopulation)? Case Controls

a. Yes, processed barns at different times (split pickup)

b. Yes, held multiple age classes but no processing during time period of 

interest

c. No, processes barns simultaneously (all-in all-out)

11. Outside Personnel and Visitors with Barn Access

Which best describes biosecurity precautions required of external personnel/visitors 

with access to chicken houses (e.g., company service representatives, health 

professionals, maintenance, technicians)? Case Controls

a. Minimal biosecurity precautions 

b. Moderate biosecurity precautions (e.g., clean clothes, hands, footwear; sitespecific gear; visitors do not enter barns unless absolutely necessary) 

c. Strong biosecurity precautions (e.g., above plus biosecurity briefing, and 

signed statement declaring any recent contact with birds)

12. Workers with Barn Access

Which best describes biosecurity precautions taken by workers with access to chicken 

houses? Case Controls
Epidemiologic and Other Analyses of HPAI/LPAI Affected Poultry Flocks June 26, 2017

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a. Minimal biosecurity precautions

b. Moderate biosecurity precautions (e.g., employees use site-specific gear, 

employees are not employed at more than one operation)

c. Strong biosecurity precautions (e.g., above plus employees do not own or 

hunt birds; employees receive biosecurity training in a language in which 

they are fluent) 

13. Foot Baths at Entry to Chicken Houses

Which best describes foot bath use and maintenance on this farm? Case Controls

a. Minimal biosecurity precautions (e.g., foot baths, hand wash stations at most 

entrances) 

b. Moderate biosecurity precautions (e.g., above plus foot baths at all 

entrances including garage doors and interior doors, use required at all 

times, no way to bypass, no pets)

c. Strong biosecurity precautions (e.g., above, plus change footbaths daily or 

more frequently if dirty, pre-wash or cover footwear to remove organics

before stepping in footbath) 

14. Egg Room Access

Does the farm unload and wheel egg carts into egg or work rooms across an outdoor 

delivery area? Case Controls

a. Yes, some biosecurity (e.g., carts cleaned at hatchery, concrete pad)

b. Yes, strong biosecurity (e.g., above, plus concrete pad cleaned/disinfected 

prior to use)

c. No, fully enclosed loading area, cleaned and disinfected between each use

15. Enclosure 

Are the chicken houses in need of repair? Case Controls

a. Yes, tears, cracks, or defects in foundations, doors, walls or curtains

b. Normal wear and tear, maintenance planned for end of production cycle

c. No visible defects

16. Water Supply

Does the farm use any untreated surface water for consumption, cooling or cleaning? Case Controls

a. Yes

b. No

17. Farming Density

Is the farm in a region densely populated by poultry farms? Case Controls

a. Densely populated by poultry farms (> 3 facilities per square mile)

b. Moderately populated by poultry farms (1-3 facilities per square mile)

c. Sparsely populated by poultry farms (< 1 facility per square mile)

18. Environment (geology, wetlands, etc.)

What best describes the environment of the farm? Case Controls

a. A wetland, stream, or marshy area on the property or adjacent property with

large congregations of waterfowl

b. A wetland, stream or marshy area on the property or adjacent property 

without large congregations of waterfowl

c. Dry
Epidemiologic and Other Analyses of HPAI/LPAI Affected Poultry Flocks June 26, 2017

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19. Raccoon, skunk, or similar wildlife

Was there any indication of raccoon, skunk or similar wildlife disturbance (e.g., 

tracks/scat indoors, under the slats, or at entrances, or evidence of predation)? Case Controls

a. Yes

b. No

20. Wild birds

Was there any evidence of any wild bird disturbance (e.g., nesting in the eaves, or 

found indoors) Case Controls

a. Yes

b. No

21. Rodents

Was there clear evidence of rodent infestation? Case Controls

a. Heavy infestation (e.g., rodents seen inside during daylight, or visible 

damage to grounds or curtains)

b. Some infestation (e.g., rodents present, but low numbers)

c. None observed 

22. Curtain Siding

Does the farm have curtain siding? Case Controls

a. Yes, curtain siding

b. No, solid side walls
Epidemiologic and Other Analyses of HPAI/LPAI Affected Poultry Flocks June 26, 2017

USDA APHIS VS 36

Part Two: Hypothetical Scenario 

In this section, you’ll answer the same series of questions about a hypothetical scenario.

Imagine a hypothetical setting and industry that is very much like what currently exists in the affected region 

of Tennessee, Alabama, Georgia and Kentucky. Let’s also imagine a hypothetical outbreak of H7N9 HPAI/LPAI 

that is very much like what this region has recently experienced. The only thing that we’re going to change is 

the numbers (and names) of the operations affected: this particular mock outbreak has impacted a larger 

number of facilities. Assume that all the other defining characteristics of the outbreak (timing, weather, 

spread patterns, genotype, response, etc.) remain the same.

Next, imagine a random selection of 40 commercial broiler breeder farms (belonging to multiple companies) 

from this mock outbreak. 20 are HPAI or LPAI case farms and 20 are controls. Answer the following questions 

for this random selection of farms. Your answers are hypothetical, but should reflect your field experience and 

knowledge of the current TN/AL/KY/GA situation. Focus on the 6-8 week period before detection in the case 

farms, and the same period of time for their controls. We’ll need your responses first for the 20 case farms, 

and separately for the 20 controls.

1. Spiking Male Source Responses

How many of the 20 farms tested spiking male source populations by a protocol geared to 

detect a recent introduction of LPAI/HPAI? Cases Controls

a. Geared, including PCR in the pre-movement test, targeting sick or dead birds for 

sampling, and routinely including PCR to investigate clinical signs or drops in 

production a. a.

b. Not geared, using ACIA or serology or only sampling healthy birds for testing, or using 

only serology to investigate clinical signs or drops in production b. b.

2. Pullet Source

How many of the 20 farms sourced pullets from populations first tested by a protocol geared 

to detect a recent introduction of LPAI/HPAI? Cases Controls

a. Geared, including PCR in the pre-movement test, targeting sick or dead birds for 

sampling, and routinely including PCR to investigate clinical signs or drops in 

production a. a.

b. Not geared, using ACIA or serology or only sampling healthy birds for testing, or using 

only serology to investigate clinical signs or drops in production b. b.

3. Wind

How many of the 20 farms were situated downwind (and within a mile or so) of a source of 

infective material (e.g., positive farm, disposal location or depopulation/disposal traffic)? Cases Controls

a. Downwind a. a.

b. Not downwind b. b.

4. Habitat Disruption 

How many of the 20 farms experienced conditions that may attract local rodent/wildlife (e.g., 

sale of neighboring farms, disruption of perimeter habitats, or local feed/waste spills)? Cases Controls

a. Attraction a. a.

b. No attraction b. b.

5. Integrated Poultry Complex
Epidemiologic and Other Analyses of HPAI/LPAI Affected Poultry Flocks June 26, 2017

USDA APHIS VS 37

How many of the 20 farms were part of a poultry complex with other farm(s) subsequently 

found to be LPAI/HPAI positive? Cases Controls

a. Yes, the complex included another infected farm a. a.

b. No, the complex did not include other infected farms, but periodically had to 

externally source feed or pullets b. b.

c. No, the complex did not include other infected farms, and did not have to externally 

source feed or pullets c. c.

6. Vehicle Biosecurity

How many of the 20 farms employed biosecurity for vehicles involved in bird delivery, egg 

pickup or bird processing or disposal using precautions best described as follows? Cases Controls

a. Minimal biosecurity precautions a. a.

b. Moderate biosecurity precautions (e.g., interior and exterior of vehicles, including 

tires, are cleaned and disinfected daily) b. b.

c. Strong biosecurity precautions (e.g., interior and exterior of vehicles, including tires, 

are cleaned and disinfected between farms) c. c.

7. Operational Equipment Biosecurity

How many of the 20 farms employed biosecurity for equipment shared between farms and in 

contact with birds or eggs (e.g., farm racks, egg flats, carts, egg buggies, bird crates) using 

precautions best described as follows? Cases Controls

a. Minimal biosecurity precautions a. a.

b. Strong biosecurity precautions (e.g., cleaned and disinfected before entry to farm) b. b.

8. Farm Equipment Biosecurity (tillers, skid steers, etc)

How many of the 20 farms employed biosecurity for farm equipment used in chicken houses 

following precautions best described below? Cases Controls

a. Minimal biosecurity precautions a. a.

b. Moderate biosecurity precautions (e.g., cleaned and disinfected before entry to 

houses; if shared between farms washed after use) b. b.

c. Strong biosecurity precautions (e.g., cleaned and disinfected before entry to houses, 

no sharing between farms) c. c.

9. Shared Disposal Routes

How many of the 20 farms shared mortality disposal destinations (renderers, compost piles, 

burial pits, etc) with other farms subsequently found to be LPAI/HPAI positive? Cases Controls

a. Shared with a farm subsequently found LPAI/HPAI positive a. a.

b. Shared with other farms, but unsure which ones b. b.

c. Either (1) shared but not with farms subsequently found LPAI/HPAI positive, or (2) not 

shared with other farms c. c.

10. Catch Crews and Processing

How many farms processed their chicken houses at different times (not including

depopulation)? Cases Controls

a. Yes, processed barns at different times (split pickup) a. a.

b. Yes, held multiple age classes but no processing during time period of interest b. b.

c. No, processed barns simultaneously (all-in all-out) c. c.

11. Outside Personnel and Visitors with Barn Access

How many of the 20 farms employed biosecurity for external personnel or visitors with access 

to chicken houses (e.g., company service representatives, health professionals, maintenance, 

or technicians) using precautions best described as follows? Cases Controls
Epidemiologic and Other Analyses of HPAI/LPAI Affected Poultry Flocks June 26, 2017

USDA APHIS VS 38

a. Minimal biosecurity precautions a. a.

b. Moderate biosecurity precautions (e.g., clean clothes, hands, footwear; site-specific 

gear; visitors do not enter barns unless absolutely necessary) b. b.

c. Strong biosecurity precautions (e.g., above plus biosecurity briefing, and signed 

statement declaring any recent contact with birds) c. c.

12. Workers with Barn Access

How many of the 20 farms employed biosecurity for workers with access to chicken houses 

using precautions best described as follows? Cases Controls

a. Minimal biosecurity precautions a. a.

b. Moderate biosecurity precautions (e.g., employees use site-specific gear, employees 

are not employed at more than one operation) b. b.

c. Strong biosecurity precautions (e.g., above plus employees do not own or hunt birds; 

employees receive biosecurity training in a language in which they are fluent) c. c.

13. Foot Baths at Entry to Chicken Houses

How many of the 20 farms utilized foot baths following precautions best described as 

follows? Cases Controls

a. Minimal biosecurity precautions (e.g., foot baths, hand wash stations at most 

entrances) a. a.

b. Moderate biosecurity precautions (e.g., above plus foot baths at all entrances

including garage doors and interior doors, use required at all times, no way to bypass, 

no pets) b. b.

c. Strong biosecurity precautions (e.g., above, plus change footbaths daily or more 

frequently if dirty, pre-wash or cover footwear to remove organics before stepping in 

footbath) c. c.

14. Egg Room Access

How many of the 20 farms unload and wheel egg carts into egg or work rooms across an 

outdoor delivery area? Cases Controls

a. Yes, some biosecurity (e.g., carts cleaned at hatchery, concrete pad) a. a.

b. Yes, strong biosecurity (e.g., above, plus concrete pad cleaned/disinfected prior to use) b. b.

c. No, fully enclosed loading area, cleaned and disinfected between each use c. c.

15. Enclosure 

In how many of the 20 farms are chicken houses in need of repair? Cases Controls

a. Tears, cracks, or defects in foundations, doors, walls, or curtains a. a.

b. Normal wear and tear, maintenance planned for end of production cycle b. b.

c. No visible defects c. c.

16. Water Supply

How many of the farms use untreated surface water for consumption, cooling or cleaning? Cases Controls

a. Untreated a. a.

b. Ground or treated water only b. b.

17. Farming Density

How many of the 20 farms are in poultry regions best described as follows? Cases Controls

a. Densely populated by poultry farms (> 3 facilities per square mile) a. a.

b. Moderately populated by poultry farms (1-3 facilities per square mile) b. b.

c. Sparsely populated by poultry farms (< 1 facility per square mile) c. c.
Epidemiologic and Other Analyses of HPAI/LPAI Affected Poultry Flocks June 26, 2017

USDA APHIS VS 39

Open Response

1. What do you think is protecting the broilers and table-egg layers?

2. What do you think protected your control farm you selected in the first section?

18. Environment (geology, wetlands, etc.)

How many of the 20 farms are situated in environments best described as follows? Cases Controls

a. A wetland, stream, or marshy area on the property or adjacent property with large 

congregations of waterfowl a. a.

b. A wetland, stream or marshy area on the property or adjacent property without large 

congregations of waterfowl b. b.

c. Dry c. c.

19. Raccoon, skunk, or similar wildlife

How many of the 20 farms have indication of raccoon, skunk or similar wildlife disturbance 

(e.g., tracks/scat indoors, under the slats, or at entrances, or evidence of predation)? Cases Controls

a. Indication a. a.

b. No indication b. b.

20. Wild birds

How many of the 20 farms have evidence of any wild bird disturbance (e.g., birds nesting in 

the eaves or seen indoors) Cases Controls

a. Evidence a. a.

b. No evidence b. b.

21. Rodents

How many of the 20 farms have clear evidence of rodent infestation? Cases Controls

a. Heavy infestation (e.g., rodents seen inside during daylight, or visible damage to 

grounds or curtains) a. a.

b. Some infestation (e.g., rodents present, but low numbers) b. b.

c. None observed c. c.

22. Curtain Siding

How many of the 20 farms have curtain siding? Cases Controls

a. Curtain siding a. a.

b. Solid side walls b. b.
Epidemiologic and Other Analyses of HPAI/LPAI 

Affected Poultry Flocks

June 26, 2017 Report

USDA  APHIS  VS

Science, Technology, and Analysis Services

Center for Epidemiology and Animal Health

2150 Centre Avenue, Bldg. B, Fort Collins, CO, 80526-8117

Web: http://www.aphis.usda.gov/animal-health/ceah