# Presentation: 526690

## West Nile Virus, 2001:Southern and Western Expansion

**West Nile Virus, 2001:****Southern and Western Expansion**

**3****rd**** National West Nile Virus Planning Meeting**
**Atlanta, Georgia**
**March 22-23, 2002 **

**Notes:**
Good morning. This morning I am going to give an overview of West Nile virus surveillance in the United States in 2001

## WNV Surveillance, United States, 2001*:Order of Topics

**ArboNET overview**
**Birds**
**Mosquitoes**
**Equines**
**Humans**
**Summary & conclusions**

**Notes:**
The source of these data is ArboNET, the WNV surveillance data reporting system that was used for the first time in 2001. During this presentation I will present information on the WNV infected birds, mosquitoes, horses, and humans that were reported in 2001. Then I will wrap up with some conclusions and, if there is time, will give some information about the surveillance in Canada.

## Slide 3

**Notes:**
Everything that I am going to be talking about today is the result of our cooperators reporting to ArboNET. ArboNET currently includes all 54 cooperators who were funded in 2001 to include West Nile virus surveillance. This includes the 48 continuous states plus six large independent cities that were separately funded – Washington D.C. New York City, Philadelphia, Houston, Chicago, and Los Angeles. ArboNET electronically receives reports of humans or animals that are tested for WNV infection (so-called denominator data) and of animals that are found to be positive for infection (so-called numerator data). For those of you that have not worked with us on reporting human cases, we still insist on receiving human reports by direct phone call to DVBID in Fort Collins.  With regards to upcoming changes in ArboNET, many cooperators wanted the capacity to manage and report surveillance data about all domestic arboviruses. We will be attempting to accommodate them in 2002.

## How many states collected West Nile virus (WNV) surveillance data in 2001?

- 39 state/local jurisdictions reporting dead bird denominator data
- 35 - mosquito denominator data
- 29 - human denominator data
- 27 – veterinary/horse denominator data
- 11 - sentinel animal denominator data
-   4 - seroprevalence denominator data

- As of 3/13/2002

**Notes:**
Of the 54 state and local jurisdictions, we received “denominator” data about the collection and testing of dead birds from 39 jurisdictions. About the collection and testing of mosquitoes from 35 jurisdictions. Human denominator data was submitted from 29 jurisdictions. And horse denominator data from 27 jurisdictions.

Few jurisdictions submitted denominator data regarding sentinel animals and animal seroprevalence data.

## How much activity in 2001?

**1999****	****	****28 counties in 4 states reported**
**	****	****	****any WNV activity**
**2000****	****	****136 counties in 12 states & DC**
**	****	****	****reported any WNV activity**
**2001****	****	****358 counties in 27 states & DC**
**	****	****	****reported any WNV activity**

**Notes:**
So, how much activity did we see? In 2001 we received reports of WNV infected animals in 358 counties in 27 states and the District of Columbia ... a tremendous increase over 2000 when we first established WNV surveillance.

## CDC Surveillance Regions

**PAC**

**MTN**

**WNC**

**WSC**

**ENC**

**N Engl**

**S Atl**

**ESC**

**Mid-Atl**

**Notes:**
For this talk I am going to present a regional view of activity. I will be using CDC Surveillance regions. For those of you who are not familiar with these regions, here they are. There are a total of nine regions. Today I will be presenting data from 7 of the 9 regions. ... New England, the mid-Atlantic (NY, NJ, PA), the south Atlantic region (which extends from Maryland and Delaware to Florida), and the 4 regions that comprise the central part of the United States.

## States Reporting WNV-Positive Dead Birds, 2001*

*** As of 3/13/2002**

**DC**

**7,338 birds**
**328 counties**
**27 states & DC**

**Notes:**
In 2001, more than 7300 WNV-positive birds were reported from 27 states and DC which are shown here in red. Infected birds were reported from 328 of the 358 counties that reported any activity in 2001. Most of the birds were reported from the two regions that reported activity in 1999 and 2000 – the New England and Mid-Atlantic regions. But, for the first time ever, infected birds were reported from the South Atlantic, the East South Central, the West South Central, the East North Central and the West North Central regions. .... With more than 2500 birds reported from the South Atlantic region.

## WNV Surveillance, United States, 2001*:Summary of Dead Bird Data

**69,102 dead birds reported**
**32,918 tested (48% of reported)**
**7,338 WNV-positive (22% of tested)**
**5,161 in genus *****Corvus***** (71%)**
**2,177 in other genera (29%)**
**54% of tested crows “positive”**
**9% birds from other species “positive”**

*** As of 3/13/2002**

**Notes:**
In 2001, cooperators collected reports on about 69,000 dead birds. They tested about 33,000 or 48% of the reported birds. Of these 33,000 birds 22% were found to be infected. The majority of positive birds were still crows – in fact, 71% of the positive birds were crows while 29% of the positives were in other genera. In 2001, the crow remained an important part of the avian mortality surveillance. Nationwide, of the nearly 10,000 crows that were tested, 54% were found to be positive. This compares to 9% of all other birds that were tested and found to be positive.

## U.S. counties reporting any West Nile virus-infected

**birds** in **1999** (N = 28 counties)

**Notes:**
Here is the first time series. Just to recap 1999 when infected birds in 4 states (primarily American crows) were reported from 28 counties shown here in blue.

## U.S. counties reporting any West Nile virus-infected

**birds** from **Jan - May 2000** (N = 4 counties)

**Notes:**
In 2000, several counties reported positive birds early in the year. So, by May of 2000 we already had 4 counties reporting positive birds. But, for the most part, these positives still occurred in the metropolitan area  of New York City.

## U.S. counties reporting any West Nile virus-infected

**birds** from **Jan - Jul 2000** (N = 40 counties)

**Notes:**
By July of 2000, we had reports from 40 counties and we start to see quite a bit of spread from the NYC metro area.

## U.S. counties reporting any West Nile virus-infected

**birds** from **Jan - Aug 2000** (N = 88 counties)

**Notes:**
By August 2000, there were reports from 88 counties but it still involved a relatively small area in the New England and Mid-Atlantic regions.

## U.S. counties reporting any West Nile virus-infected

-  **birds** from **Jan - Sep 2000** (N = 122 counties)

**Notes:**
By September 2000, we had heard from 122 counties and there was significant expansion into PA, MD, VA, and NC.

## U.S. counties reporting any West Nile virus-infected

**birds** from **Jan - Oct 2000** (N = 134 counties)

**Notes:**
By October .... 134 counties ... more counties in the Baltimore and DC metro areas were identified.

## U.S. counties reporting any West Nile virus-infected

**birds** from **Jan - Dec 2000** (N = 136 counties)

**Notes:**
Here are all the counties that reported infected birds in 2000 .... 136 of them ... stretching from northern NY state to the middle of NC but predominating on the Atlantic coast.

## U.S. counties reporting any West Nile virus-infected

**birds** from **Jan - May 2001** (N = 11 counties)

**Notes:**
Now, let’s look at 2001 data. What we received were almost the simultaneous reports of “first birds” from 11 counties in 5 different states ... but all were states that had reported activity in 2000.

## U.S. counties reporting any West Nile virus-infected

**birds** from **Jan - Jun 2001** (N = 22 counties)

**Notes:**
In June 2001, there was an important development. Positive birds were reported from two southern states – Georgia and Florida – states that had not reported WNV activity prior to 2001.

## U.S. counties reporting any West Nile virus-infected

**birds** from **Jan - Jul 2001** (N = 82 counties)

**Notes:**
By July of last year, one gets the idea that there are two foci of epizootic activity – one continuing for another year in the northeast and a new focus along the Georgia-Florida border. In addition, positive birds were reported from northeast Ohio and southeast Wisconsin in July ... another big finding ... moving into the mid-west. 

## U.S. counties reporting any West Nile virus-infected

**birds** from **Jan - Aug 2001** (N = 200 counties)

**Notes:**
By August 2001, 200 counties reported infected birds. In August there was a tremendous increase in the number of midwestern counties and through the counties of southern Florida all the way down to Dade County.

## U.S. counties reporting any West Nile virus-infected

**birds** from **Jan - Sep 2001** (N = 298 counties)

**Notes:**
By September, nearly 300 counties reported dead, infected birds. The advancing edge of reported birds has extended to the Arkansas-Oklahoma border and new counties along the Mississippi River and its tributaries – counties in Iowa, Missouri, Tennessee, and Louisiana.

## U.S. counties reporting any West Nile virus-infected

**birds** from **Jan - Oct 2001** (N = 327 counties)

**Notes:**
Through October .... 327 counties ..... Filling in the counties of Florida and one continuous group of counties extending along the Atlantic coast from Maine to Maryland.

## U.S. counties reporting any West Nile virus-infected

**birds** from **Jan - Dec 2001** (N = 328 counties)

**Notes:**
So, here, shown in red, are the 328 counties that reported dead, infected birds in 2001 and I think you can appreciate the tremendous western and southern expansion of reported birds since 2000.

## No. of WNV-Positive Crows Reported,Mid-Atlantic, New England, & South Atlantic Regions, by Week, 2001*

**Week ending**

***As of 2/1/02**

**Notes:**
On this graph, I am showing the number of infected birds by week of collection for three regions – the mid-Atlantic shown in green, New England shown in blue, and the South Atlantic region in red. What I would like you to notice is the big increase in the number of infected crows in the Mid- and South Atlantic regions and that these increases start at approximately the same time ... the last week of June. In New England, the increase started a little later but more rapidly increased and may have ended a little earlier as well.

## No. of WNV-Positive Crows Reported, North Central & South Central Regions, by Week, 2001*

***As of 2/1/02**

**Notes:**
Same type of graph for the four central regions where positive birds were not seen until the middle of August or later.

## States Reporting WNV-Positive Mosquito Pools, 2001*

*** As of 3/13/2002**

**918 pools**
**27 species**
**16 states & D.C.**

**DC**

**Notes:**
Moving onto mosquitoes. In 2001, there were 918 WNV-infected pools reported from 16 states and the DC shown in red. Interestingly, there were 27 different species reported to be infected in 2001. The vast majority of the positive mosquitoes were reported from the mid-Atlantic region which included NY, NJ, and PA.

## 918 WNV-positive mosquito pools

27 positive species

543 pools (59%) Cx pipiens, Cx restuans, or mixed
70 (8%) Cx salinarius

Earliest: Cx pipiens, 31 MAY, Middlesex County, NJ

Latest: Cx pipiens, 25 OCT, Camden County, NJ

**27 positive species**
**543 pools (59%) *****Cx pipiens,***** *****Cx restuans, *****or mixed**
**70 (8%) *****Cx salinarius***
**Earliest: *****Cx pipiens*****, 31 MAY, Middlesex County, NJ**
**Latest: *****Cx pipiens*****, 25 OCT, Camden County, NJ**

*** As of 3/13/2002**

**Summary of Mosquito-Based WNV Surveillance,****United States, 2001***

**Notes:**
Of the 918 pools, 613 or 67% were three Culex species – 543 or 59% were Culex pipiens or Cx restuans and 70 or 8% were Cx salinarius.

The first positive pool was a pool in 2001 was a pool of Cx pipiens collected on 5/31 in Middlesex County NJ.
The last positive pool was also a pool of pipiens collected on October 25 in Camden County NJ.

## WNV-Positive Mosquito Species Reported,United States, 2001*

**WNV-Positive Mosquito Species Reported,****United States, 2001***

| Culex | Aedes | Ochlerotatus | Anopheles | Other |
| --- | --- | --- | --- | --- |
| pipiens    restuans quinq salinarius nigripalpus | albopicutus
cinereus
vexans | atlanticus canadensis cantator japonicus sollicitans taeniorhynchus triseriatus trivittatus | barberi
punctipennis
atropos 
crucians
quadrimaculatus
 | Cs. melanura
Cq. perturbans
Deinocerites cancer
Ps. columbiae
Orthopodomyia signifera
Uranotaenia sapphirina |

**Notes:**
Here is a list of the 27 mosquito species that were reported in 2001. There are 11 species in the genera Aedes and Ochlerotatus; 5 anopheles species; 5 culex species; and a smattering of other species including Culiseta melanura and Coquillitidia perturbans.

## U.S. Counties Reporting WNV-Positive Mosquitoes

**U.S. Counties Reporting WNV-Positive ****Mosquitoes**

***1999***
**8 counties**

**Notes:**
So, here are the time series. In 1999, positive mosquitoes were reported from 8 counties.

## U.S. Counties Reporting WNV-Positive Mosquitoes

***2000***
***JAN - JUL***
**6 counties**

**U.S. Counties Reporting WNV-Positive ****Mosquitoes**

**Notes:**
From January through July of 2000, there were 6 counties .... Still all in the NYC metro area.

## U.S. Counties Reporting WNV-Positive Mosquitoes

***2000***
***JAN - AUG***
**19 counties**

**U.S. Counties Reporting WNV-Positive ****Mosquitoes**

**Notes:**
By August 2000, there were 19 counties and we were getting more reports from counties away from the NYC metro area.

## U.S. Counties Reporting WNV-Positive Mosquitoes

***2000***
***JAN - SEP***
**27 counties**

**U.S. Counties Reporting WNV-Positive ****Mosquitoes**

**Notes:**
Through September, there were 27 counties.

## U.S. Counties Reporting WNV-Positive Mosquitoes

***2000***
***JAN - DEC***
**33 counties**

**U.S. Counties Reporting WNV-Positive ****Mosquitoes**

**Notes:**
And, by the end of 2000, we had reports of positive mosquitoes from 33 counties including a pool of Culex pipiens that was collected in Erie County NY very late in the year. 

## U.S. Counties Reporting WNV-Positive Mosquitoes

**U.S. Counties Reporting WNV-Positive ****Mosquitoes**

***2001***
***JAN - JUN***
**6 counties**

**Notes:**
Here are the 2001 data. From January through June, 5 counties in New Jersey and New York reported positives. But, right from the start we are starting to see positive pools from a county in the panhandle of Florida.

## U.S. Counties Reporting WNV-Positive Mosquitoes

**U.S. Counties Reporting WNV-Positive ****Mosquitoes**

***2001***
***JAN - JUL***
**32 counties**

**Notes:**
Through July, 32 counties had reported positive mosquito pools. And, what you begin to see are the two epizootic foci emerging. And, in 2001, we have an early-year report of a positive pool being reported from Erie County NY.

## U.S. Counties Reporting WNV-Positive Mosquitoes

**U.S. Counties Reporting WNV-Positive ****Mosquitoes**

***2001***
***JAN - AUG***
**61 counties**

**Notes:**
Through August 2001, 61 counties had reported positive pools of mosquitoes.

## U.S. Counties Reporting WNV-Positive Mosquitoes

**U.S. Counties Reporting WNV-Positive ****Mosquitoes**

***2001***
***JAN - DEC***
**71 counties**

**Notes:**
So, here are all the 71 counties that reported positive pools of mosquitoes in 2001. 

## Non-Human Mammals Reported WNV-Infected, United States, 1999-2001

| 
Species | 
# Infected | WNV
Disease |
| --- | --- | --- |
|  |  |  |
| Horse | ~700 | Yes |
| Cat | 1 | ? |
| Domestic rabbit | 1 | ? |
| Gray Squirrel | 1 | ? |
| Eastern Chipmunk | 1 | ? |
| Striped Skunk | 1 | ? |
| Big Brown Bat | 1 | ? |
| Little Brown Bat | 1 | ? |

**Notes:**
Moving on to non-human mammals. First here is a list on non-human mammal species that have been reported to be infected since 1999. I wanted to point out that several species that were reported as positive in 2000 have been removed from this list because they were withdrawn by the reporting states. So, raccoons and a couple of bat species have been removed.

## States Reporting Equine WNV Disease Cases, 2001*

*** As of 3/13/2002**

**731 cases**
**125 counties**
**19 states**

**Notes:**
This was an incredible year in terms of the number of horse cases that were reported to ArboNET. In 2001, the only infected non-human mammals that were reported were horses. In 2001, 731 infected and ill horses were reported from 125 counties in 19 states which are shown in red here. States in the South Atlantic region reported 569 ill and infected horses and Florida alone has reported 483 ill and infected horses.

## U.S. counties reporting equine WNV illnesses1999 (N = 2 counties)

**Notes:**
I’ll go through these series quickly. In 1999, horses with WNV illnesses were only reported from two counties shown in blue.

## U.S. counties reporting equine WNV illnessesJan - Aug 2000 (N = 6 counties)

**Notes:**
Here are the 2000 maps. From January through August 2000, six counties.

## U.S. counties reporting equine WNV illnessesJan - Sep 2000 (N = 19 counties)

**Notes:**
Through September, one month later, 13 additional counties for a total of 19 counties.

## U.S. counties reporting equine WNV illnessesJan - Oct 2000 (N = 26 counties)

**Notes:**
Through October, 26 counties.

## U.S. counties reporting equine WNV illnessesJan - Dec 2000 (N = 26 counties)

**Notes:**
And, from January through December 2000, 26 counties in 6 states reported infected and ill horses. The majority of these horses were reported relatively late in the year.

## U.S. counties reporting equine WNV illnessesJan - Jul 2001 (N = 9 counties)

**Notes:**
Here are the 2001 data.
Right from the start, there are big changes. From the last week of June through the end of July, 9 counties reported infected and ill horses. The first reported horse had illness onset on June 27, 2001 from Jefferson County, Florida.

## U.S. counties reporting equine WNV illnessesJan - Aug 2001 (N = 36 counties)

**Notes:**
Through August, there were 36 counties including counties in Louisiana, Kentucky, Alabama, and Virginia.

## U.S. counties reporting equine WNV illnessesJan - Sep 2001 (N = 84 counties)

**Notes:**
Through September there were 84 counties reporting ill and infected horses.

## U.S. counties reporting equine WNV illnessesJan - Oct 2001 (N = 119 counties)

**Notes:**
Through October ... 119 counties

## U.S. counties reporting equine WNV illnessesJan - Nov 2001 (N = 124 counties)

**Notes:**
November ..... 124 counties

## U.S. counties reporting equine WNV illnessesJan - Dec 2001 (N = 125 counties)

**Notes:**
And in December one more new county reported an infected horse for a total of 125 counties reporting ill and infected horses in 2001.

The last reported horse had illness onset on December 18, 2001 and was reported from Lake County, Florida

## States Reporting Human WNV Disease Cases, 2001*

*** As of 3/13/2002**

**66 cases**
**39 counties**
**10 states**

**Notes:**
In 2001, 66 human illnesses attributed to WNV were reported to ArboNET. Of these, 64 were severe neurologic illnesses in which people were hospitalized while 2 appeared to have West Nile fever. And, just to let you know, we are still working with cooperators to sort out a few more possible cases. So, this number may change in the coming weeks. Most human cases were reported from the Mid Atlantic region which included NY, NJ, and PA where 30 human illnesses were reported. The south Atlantic region reported 24 human cases of illness and the New England region reported 9 human cases. These 66 cases were reported from 39 counties in 10 states ... shown here in red.

## U.S. counties reporting human WNV illness

**1999** (N = 6 counties)

**Notes:**
In 1999, human cases were reported from 6 counties in the NYC metropolitan area.

## U.S. counties reporting human WNV illness

**2000** (N = 10 counties)

**Notes:**
In 2000, 10 counties in three states reported human illness attributed to WNV.

## U.S. counties reporting human WNV illness

**Jan - Jul 2001** (N = 5 counties)

**Notes:**
Here are 2001 data.
In July 2001, five counties reported human illness due to WNV infection. The first reported human case had illness onset on July 13 and was reported from a county in northern Florida. This was the first reported U.S. case where WNV infection was acquired outside of the NYC metro area since 1999.

## U.S. counties reporting human WNV illness

**Jan - Aug 2001** (N = 22 counties)

**Notes:**
Through August 2001, 22 counties in 8 states reported human cases. 

## U.S. counties reporting human WNV illness

**Jan - Sep 2001** (N = 33 counties)

**Notes:**
Through September, 33 widely dispersed counties reported human cases.

## U.S. counties reporting human WNV illness

**Jan - Oct 2001** (N = 38 counties)

**Notes:**
Through October ... 38 counties.

## U.S. counties reporting human WNV illness

**Jan - Dec 2001** (N = 39 counties)

**Notes:**
Here is a map of the 39 counties that reported human cases in 2001.

The last human case reported to ArboNET had illness onset on December 7, 2001 and was reported from a county in southern Georgia.

## Reported Human WNV Disease Cases,United States, 1999-2001*

*** As of 3/13/2002**

| Year | Cases | States | Counties | Onset Dates |
| --- | --- | --- | --- | --- |
| 1999 | 62 | 1 | 6 | 2 AUG – 24 SEP |
| 2000 | 21 | 3 | 10 | 20 JUL – 27 SEP |
| 2001 | 66 | 10 | 39 | 13 JUL – 7 DEC |

**Notes:**
So, to summarize the human time series. In 2001, 66 cases were reported from 39 widely-dispersed counties in 10 states. Illness onset ranged from July 13 to December 7. No single county reported more that 3 human cases.

## Human WNV Disease Cases, by Week of Onset, United States, 1999-2001*

*** As of 3/13/2002**

**Notes:**
Here are the epi curves for 1999 though 2001 with the number of reported human cases by week of illness onset. The Y-axis shows the number of cases and the x-axis shows the week. Compared to 1999 and 2000, the transmission season to humans was longer in 2001. Unlike previous years, we had several cases that  occurred in October and later. This is not all due to the expansion into the southern states. 

## Human WNV Disease Cases, by Week of Illness Onset, “Northern” vs. “Southern” United States, 2001*

*** As of 3/13/2002**

**7/7**

**8/4**

**9/1**

**9/29**

**10/27**

**11/24**

**12/23**

**Notes:**
On this slide I have given the 10 states reporting human cases a “northern” or “southern” designation. States above the Mason-Dixon line are northern and include MA, CT, NY, NJ, and PA. States below the Mason-Dixon line have been designated southern and include MD, GA, FL, AL, and LA. As you can see of the 11 cases that had illness onset in October or later, 4 occurred in northern states (including one that had illness onset in the second week of November) and 7 occurred in southern states.

## WNV Case-Patient Demographics & Mortality, United States, 1999-2001

**WNV Case-Patient Demographics & Mortality, United States, 1999-2001**

|  | 1999-2000 | 2001* |
| --- | --- | --- |
| n | 83 | 66 |
| Age (yr) |  |  |
|     median | 65 | 68 |
|     range | 5 – 90 | 19 - 90 |
| Males | 54% | 65% |
| CFR | 11% | 14% |

**Notes:**
Among the 66 cases that were reported in 2001, the median age was 68 years with a range of 19 to 90 years. In 2001, there were 9 deaths attributed to the WNV infection a case fatality ratio of 14%. As you can see, there is no significant difference in the proportion of males or the CFR between the 1999/2000 cases and the 2001 cases.

## Summary of any WNV Activity,United States, 1999-2001*

| Year | States | Counties | Date Range |
| --- | --- | --- | --- |
| 1999 | 5 | 28 | 9 AUG – 15 NOV |
| 2000 | 13 | 145 | 6 FEB – 17 NOV |
| 2001 | 28 | 358 | 8 APR – 26 DEC |

**Summary of **_**any**_** WNV Activity,****United States, 1999-2001***

**Notes:**
Here is a summary slide that shows the earliest and latest surveillance event in 1999, 2000, and 2001. As you can see the latest activity in 2001 occurred on December 26 when a dead infected crow was collected in one of the South Atlantic states. 

In January and February 2002, a South Atlantic state has already reported infected birds and horse. So, as was predicted by many, year-around transmission has gone from being a potential problem to a real problem.

## *

** ****Western-Most U.S. Counties Reporting WNV-Positive Bird**
**2001,**** ****2000,**** ****1999**

*****

*****

*****

**1****st**** human cases, 1999**

**Notes:**
This slide demonstrates the westward spread of REPORTED avian activity in 99, 2000, and 2001. Between 2000 and 2001, reported activity spread westward approximately 800 miles.

## *

*****

**1****st**** human cases, 1999**

** ****Southern-Most U.S. Counties Reporting WNV-Positive Bird**
**2001, ****2000, ****1999**

**Notes:**
This slide demonstrates the southward spread of REPORTED avian activity in 99, 2000, and 2001. Between 2000 and 2001, reported activity spread southward approximately 750 miles.

In 2001, although there were infected birds reported in Canada from southeast Ontario, this activity was actually further south than the northeastern U.S. activity reported in 2000 and 2001. There was no northward extension of the area reporting WNV activity.

## WNV-Infected Crows, Horses, Mosquitoes, & Humans,

**WNV-Infected Crows, Horses, Mosquitoes, & Humans,**
**South Atlantic Region, U.S., by MMWR Week, 2001***

*** As of 3/13/2002**

**Notes:**
This graph shows the epi-curves for horses, crows, any mosquito species and humans in the South Atlantic region. The only point that I wanted to make here is that a lot of the “first” events (such as first bird, first horse, and even first human) occur almost simultaneously. So, to take advantage of the dead birds as “sentinel events” of WNV activity, these specimens must be collected, tested, and reported quickly.

## Slide 66

**Notes:**
Same type of graph and same point using mid-Atlantic data.

## Lead Time from WNV Surveillance Event to 1st Human Case, 39 Counties,United States, 2001*

|  | “1st positive” before 1st human |  |  |  |
| --- | --- | --- | --- | --- |
|  | Bird | Horse | Mosquito | Epidemic Vector |
| Counties | 36 | 11 | 22 | 10 |
| Mean (days) | 51 | 34 | 36 | 26 |
| Median (days) | 50 | 28 | 34 | 25 |
| Range (days) | 1 - 118 | 3 - 85 | 12-76 | 6 - 71 |

*** As of 3/13/2002**

**Notes:**
So, what system is the best animal surveillance system for showing increasing human risk? 

We haven’t integrated the denominator data into such an analysis yet so we do not know yet. But, I did want to give you an idea of the number of days between a “first” positive animal surveillance event and the illness onset of the first human case in the 39 counties reporting human cases.

Of the 39 counties reporting human cases in 2001, all 39 had bird surveillance in place. 36 (92%) had a positive bird prior to the illness onset of the first human case. In 24 of the 36 counties, the first bird was a crow and in 12 of the 36, the first bird was a species other than a crow. In these 36 counties, the median number of days of lead time was 50 days but had a range from 1 to 118 days.

Of the 39 counties reporting a human cases in 2001, only 23 reported horse denominator data so we know they had a veterinary surveillance system in place. Of these 23,  11 (48%) had an ill and infected horse prior to the first human case.  The median number of days of lead time was 28 days with a range of 3-85 days.

Similarly, of the 29 counties that reported a human case AND any mosquito denominator data, 22 (76%) collected an infected mosquito pool prior to the illness onset of a human case. The median number of days of lead time was 34 days with a range of 12-76 days.

Of the 20 counties that reported denominator data for potential epidemic vectors (for example Cx salinarius, Aedes or Ochlerotatus spp.), 10 (50%) had a positive potential epidemic vector pool prior to the human illness onset. The median was 25 days prior with a range of 6-71 days.

So, I think it is safe to say that avian mortality surveillance remains a sensitive but relatively nonspecific predictor of human cases. But, Dr. Steve Guptill will be addressing that later this morning.

## National WNV Surveillance, 2001:Conclusions

**Dramatic southward & westward expansion since 1999**
**Two major transmission foci in 2001: northeast & southeast**
**WNV probably entered Florida/Georgia in 2000**
**Major equine epizootic in 2001, especially in South Atlantic region**
**Only sporadic human cases despite intense epizootic in some areas**
**Prolonged transmission season observed**
**Bird and crow surveillance remain effective**

**Notes:**
So, from these data, what are some of the conclusions?
Dramatic southward and westward expansion of viral activity since 1999
Although we still need to incorporate the denominator data into the analysis, it appears that there were two major transmission foci in 2001 -- one in the northeast (where it has now persisted for 3 years) and one in the southeast. 
Because of the rapid build-up in the number of animal and human infections in the southeast, we must strongly consider that WNV was introduced to GA and FL in the end of the 2000 season and then over-wintered.
A huge equine epizootic occurred in 2001 throughout the South Atlantic region except in the Carolinas.
Only sporadic human cases occurred despite an intense epizootic over 27 states and DC.
In 2001, we experienced a prolonged transmission season and the beginning of year-round transmission in the south.
And lastly, bird and crow surveillance appear to remain a valuable component in the prediction of human cases.

## Canada:Summary of WNV Surveillance, 2001*

**Birds collected / tested in 7 provinces (PEI to Saskatchewan)**
**WNV-positives detected in S.E. Ontario (Windsor, London, & Toronto) **
**Of 2,592 birds tested, 121 (5%) WNV-positive**
**American crow  --  100/1449 (7%)**
**Bluejay  --  21/1056 (2%)**
**Common raven  --  0/61**
**Black-billed magpie  --  0/14**
**Other species  --  0/12**
**No human disease reported**

*** Provided by Health Canada**

## Slide 70

## Acknowledgements

**ArboNET:  Scores of partners in state and local health departments**
**DVBID/CDC:**
**Jennifer Lehman**
**Aaron Kipp**
**Veronica Elko**
**Kimlea Medlin**
**Dan O’Leary**
**John Jones**
**Roger Nasci**
**Chet Moore**
**Kathleen Julian**
**Mike Bunning**
**Steve Hinten**

**Notes:**
I would like to acknowledge the effort made by scores of ArboNET partners in the state and local jurisdictions who submitted these data.

Then the ArboNAUTS -- people from DVBID who have worked very hard accepting these data. Needless to say, it was not a seemless process. I accidentally omitted Kimlea Medlin from the DVBID group of ArboNAUTS. Not shown here are Tim Morris and John Loonsk (CDC’s Office of the Director) who worked extensively with us to develop ArboNET.

## Slide 72

**Notes:**
Thank you and if there is time I will take some questions.