The document summarizes West Nile virus activity in Brazos County, Texas in 2012. It finds that 71 mosquito pools tested positive for West Nile virus in the county, with the most positive pools found in Bryan (22) and College Station (26). It also reports that Brazos County had 7 cases of West Nile neuroinvasive disease and 5 cases of West Nile fever in humans that year, with no related mortalities. The document provides background on West Nile virus symptoms, testing methodology used in Brazos County, and historical West Nile virus data for the county and surrounding regions.

1. West Nile Virus in Brazos County 2012
Mark M. Johnsen Ph.D.
Environmental Health Services
Brazos County Health Department

3. West Nile Virus
• West Nile Neuroinvasive Disease (WNND) –
severe disease that affects the nervous system
(West Nile meningitis, West Nile encephalitis, and West Nile
meningoencephalitis)
• West Nile Fever (WNF) – cases that show no
evidence of neuroinvasion

4. WNV Human Infection “Iceberg”
<1% ~10% fatal
CNS (<0.1% of total infections)
disease
Crude estimates
~20%
“West Nile Fever”
~80%
Asymptomatic

5. Symptoms in Humans
Symptoms manifest 4 to 10 days after being bitten by an infected mosquito
Flu-like Symptoms
• Fever • Pain associated with eye movement
• Headache • Irritability
• Sore throat • Memory Loss
• Nausea and vomiting • Stiffness
• Confusion • Weakness
• Disorientation • Paralysis
• Sore throat • Seizures
• Diarrhea • Coma
• Drowsiness • Death
• Photophobia

6. WNV Activity in the United States 2012

7. WNV Activity in the United States 2012
• 4,531 human cases in 2012
– 2,293 WNND
– 2,238 WNF
– 183 Mortalities
• Texas is responsible for 37% of WNV human cases
State Number of Human Cases
Texas 1,683
California 285
Louisiana 239
Mississippi 229
South Dakota 200

9. Top Five Counties
County Mortalities WNND WNF Total
Dallas County 18 169 206 375
Tarrant County 10 104 152 256
Denton County 2 51 120 171
Travis County 3 56 73 129
Collin County 4 22 36 58
Harris County 4 35 23 58

10. Trapping Data
• Brazos County divided into 4 regions (College Station, Bryan, Texas
A&M University, Unincorporated Brazos County)
• Three permanent sites
• 7-9 Traps set weekly
• 147 Traps set in Brazos County in 2012
• 52 Bryan
• 46 College Station
• 39 TAMU campus
• 10 Unincorporated areas

11. Southern House Mosquito
Culex quinquefasciatus
Gravid Trap
Asian Tiger Mosquito
Aedes albopictus

13. Trapping Data
• 32,721 mosquitoes trapped for testing
• 71 WNV positive mosquito pools
– 22 Bryan
– 26 College Station
– 23 TAMU
– 0 Unincorporated areas of Brazos County

14. Positive Mosquito Pools
County Positive Mosquito Pools
Harris County 493
Dallas County 267
Travis County 127
Wichita County 28
Brazoria County 11
Orange County 7

16. West Nile Virus Activity in Brazos County
Year Human WNND Human WNF Mortalities Mosquito Bird Horse Total
0
2002 0 0 15 3 2 20
0
2003 5 0 15 2 7 29
0
2004 1 0 2 3 5 11
0
2005 0 3 14@ 14 1 33
0
2006 7 7 25 7 4 50
1
2007 1 1 2 1 0 5
1
2008 4 1 25 2 0 32
0
2009 0 0 1 0 0 1
0
2010 0 0 0 0 0 0
0
2011 0 0 0 0 0 0
0
2012# 7 5 71 0 1% 85
As of October 23, 2012

18. 4
5
8
1
6

19. WNV Human Cases
West Nile Virus Activity in Brazos County
WNV Mosquito Cases
12
11
10
9
8
Number of Cases
7
6
5
4
3
2
1
0
Trapping Weeks

20. Article was written on August 3, 2012
The golf course was positive for
its 8th week in a row.

21. Questions?
• City of College Station
– Marshall Wallace
– Barbara Moore
• City of Bryan
– Bob Holmes
– Cody Cravatt
• TAMU
– Tracy Carroll
– Jason Alexander
– Kristen Robinson