Epi Weeks 46 and 47 | November 13 - November 26, 2022

 Weeks 46 and 47* Summary 

• 3 mosquito pools from Wilco have been tested by DSHS from weeks 46 and 47
  • *Trapping did not occur week 47 due to holiday
• 0 mosquito pool tested positive for WNV in weeks 46 or 47.
• There have been 0 reported human cases of West Nile disease in Wilco in 2022
• There have been 3 human dengue cases (travel related) in Wilco in 2022
• There have been 0 human cases of SLE, Zika, CHIKV  in Wilco in 2022
• Average number of mosquitoes/trap include:
  • Culex quinquefasciatus: < 1

QA= Quality Assurance 
Wilco: Williamson County
DSHS: Texas Department of State Health Services
WNV= West Nile virus; CHIKV= chikungunya virus; SLE= St. Louis encephalitis
Arbovirus= Arthropod-borne virus

Figure 1. WILCO Mosquito Trap Map*, 2022

Williamson County Region WNV Positive Year to Date Summary

• There have been 4 WNV-positive mosquito pools in 2022
• There have been no reported human cases of WNV

WNV= West Nile virus; WNND= West Nile neuroinvasive disease
PVD= presumptive viremic blood donors are people who had no symptoms at the time of donating blood through a blood collection agency, but whose blood tested positive when screened for the presence of WNV. Some PVDs may develop symptoms after donation.

Table 1. Cumulative Data for Williamson County, Weeks 45-47

* Other potential (Culex) vector species may be tested if collected, but the primary vector for WNV in Wilco is Culex quinquefasciatus. 
1. MLE= Maximum Likelihood Estimate or the estimate of the mosquito infection rate per mosquito species calculated using a Maximum Likelihood Estimation (MLE). Biggerstaff, Brad J. PooledInfRate, Version 4.0: a Microsoft® Office Excel© Add-In to compute prevalence estimates from pooled samples. Centers for Disease Control and Prevention, Fort Collins, CO, U.S.A., 2009
2. Vector Index is a measure of infectivity that accounts for vector species composition, vector species population density, and vector species infection rates. The VI reflects the MLE adjusted for Culex quinquefasciatus abundance. 

Table 2. Central Texas West Nile Virus Activity as Reported by DSHS as of November 26, 2022

1. Mosquito surveillance not routinely conducted in this county.

WNV= West Nile virus; WNF= West Nile fever; WNND= West Nile neuroinvasive disease

PVD= presumptive viremic blood donors are people who had no symptoms at the time of donating blood through a blood collection agency, but whose blood tested positive when screened for the presence of WNV. Some PVDs may develop symptoms after donation.

Table 3. Other Central Texas Arbovirus* Activity as Reported by DSHS as of November 26, 2022

1. Mosquito surveillance not routinely conducted in this county
CHIKV= Chikungunya virus; DENV= Dengue virus; SLEV= St. Louis encephalitis virus; ZIKV= Zika virus
*All reported CHIKV, DENV, and ZIKV human cases are travel-related

For Additional Information Please Visit the Links Below:
Department of State Health Services
Arbovirus Activity Reports
Texas West Nile Virus

Williamson County and Cities Health District 
Integrated Vector Management Home Page 

Centers for Disease Control and Prevention 
West Nile virus
Integrated Mosquito Management

Environmental Protection Agency 
Insect Repellent Information