West Nile Resources

What is West Nile virus?

West Nile virus is a virus commonly found in Africa, West Asia and the Middle East.  It is not known how long it has been in the United States, but the Centers for Disease Control and Prevention (CDC) believe the virus probably has been in the eastern United States since early summer 1999.  It is closely related to the St. Louis encephalitis virus found in the United States.  The virus can infect humans, birds, mosquitoes, horses and some other animals. 

How can I reduce my risk of getting West Nile virus?

Preventing mosquito bites is the best way to avoid becoming infected with the West Nile virus. Remember the "Four D's" of Defend, Dress, Dusk to Dawn, and Drain


  • Defend yourself by applying an approved mosquito repellent.
    • Spray exposed skin and clothing with repellent. 
    • Click here for information on choosing an appropriate repellent. 
  • Dress in long sleeves and long pants when you are outside. 
  • Stay indoors from the period of dusk through dawn, times when infected mosquitoes are most active.
  • Drain standing water in your yard; old tires, flower pots and clogged rain gutters are mosquito breeding sites.
  • Also very important to be sure that doors and window are sealed properly and that screens are in place to protect your home from intruding mosquitoes.

What are the symptoms of West Nile virus?  
Most people infected with West Nile virus will not have any signs of illness.  Twenty percent of people who become infected will have only mild symptoms such as fever, headache, body aches and occasionally a skin rash on the trunk of the body.

The symptoms of severe infection (West Nile neuroinvasive disease) include headache, high fever, neck stiffness, disorientation, muscle weakness and paralysis.  Only about 1 out of 150 people infected with West Nile virus will develop this more severe form of the disease.  

The incubation period of West Nile virus in humans is 3-14 days.  Symptoms of mild disease may last a few days.  Symptoms of severe disease may last several weeks, although neurological effects may be permanent.  Rarely, death can occur.

How is it spread?
West Nile virus is spread by the bite of an infected mosquito and can infect people, horses, many types of birds and some other animals.  There is no evidence that West Nile virus can be spread from person to person or from animal to person.

Who is at risk for West Nile virus?
People older than 50 have the highest risk of severe disease and people with with weakened immune systems are at an increased risk for West Nile virus.

How likely am I to be bitten by an infected mosquito?
Less than 1 percent of those bitten by infected mosquitoes become severely ill. If you have the symptoms mentioned above, contact your doctor immediately.

Please take a moment to review this interactive video to learn more about mosquitoes and how you can reduce mosquito breeding sites on your property.


Additional Resources:

The Centers for Disease Control and Prevention (CDC):


Texas Department of State Health Services:



Dallas County Health and Human Services Website:


How to Repel Mosquitoes Safely


West Nile virus videos in American Sign Language:


Para Información en Espanol: