Houston Health Department

West Nile Virus


West Nile virus (WNV) is the leading cause of mosquito-borne disease in the continental United States.  It is most commonly spread to people by the bite of an infected mosquito.

There are no vaccines to prevent or medications to treat WNV in people. Fortunately, most people infected with WNV do not feel sick.

About 1 in 5 people who are infected develop a fever and other symptoms. About 1 out of 150 infected people develop a serious, sometimes fatal, illness.


The health department encourages people to use the “3D Defense” to prevent mosquito bites and reduce the risk of infection:

  • Drain: Drain standing water around your home so mosquitos don’t have a place to breed.
  • DEET: Apply EPA-approved insect repellent with the ingredient DEET.
  • Dress: Dress in long sleeves and pants while outdoors to limit exposed skin.

The Houston Health Department conducts surveillance of WNV in Houston while Harris County Public Health conducts surveillance in Harris County. Mosquito control services for the city of Houston and Harris County are provided by Harris County Public Health.


Gender Age Range Date Reported Area Case Number
Male 45-54 09/25/2018 Southwest Houston 4
Male 35-44 09/25/2018 Southeast Houston 3
Female 45-54 09/05/2018 Southeast Houston 2
Male 45-54 07/16/2018 Northeast Houston 1

Gender Age Range Date Reported Area Case Number
Male 45-54 03/06/2017 Northwest Houston 5
Male 45-54 09/13/2017 Northeast Houston 4
Male 85-94 09/09/2017 Southwest Houston 3
Male 45-54 08/03/2017 Northwest Houston 2
Female 5-14 08/11/2017 Southwest Houston 1

Gender Age Range Date Reported Area Case Number
Male 75-84 08/02/2016 Northeast Houston 2
Female 55-74 08/02/2016 Northwest Houston 1