West Nile Virus

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West Nile Virus

West Nile virus (WNV) is most commonly transmitted to humans by mosquitoes. You can reduce your risk of being infected with WNV by using insect repellent and wearing protective clothing to prevent mosquito bites. There are no medications to treat or vaccines to prevent WNV infection. Fortunately, most people infected with WNV will have no symptoms. About 1 in 5 people who are infected will develop a fever with other symptoms. Less than 1 percent of infected people develop a serious, sometimes fatal, neurologic illness.

Surveillance and Control

The Richardson Health Department staff conducts mosquito control activities year-round but increases those efforts from April through October, the most active mosquito season in North Texas.

The Health Department works along with the Texas Department of State Health Services, Dallas County Health and Human Services Department and area health departments to conduct surveillance and testing of the mosquito population for diseases including West Nile virus. Monitoring for mosquitos occurs year round.

Mosquito Testing Sites Map

Mosquito Testing Sites
Using traps designed for mosquito collection, the staff of the Health Department regularly collect mosquito samples from approximately 12 geographically dispersed locations throughout the community. These samples are submitted to a laboratory for analysis. The Health Department also works closely with the Dallas County and Collin County health departments to monitor for the incidence of mosquito borne illness in the human population. The Health Department also communicates with local health departments in neighboring communities.

Mosquito control efforts include public education, using larvicide along creeks and other stagnant bodies of water to prevent mosquito eggs from developing into adults, and monitoring and notification in neighborhoods where potential mosquito breeding areas are discovered. The City practices integrated mosquito control with the intent to disrupt the mosquito life cycle in its early stages to eliminate the number of adults, and to eliminate mosquito breeding habitats through proper water drainage.


No symptoms in most people. Most people (70-80 percent) who become infected with West Nile virus do not develop any symptoms.

Febrile illness in some people. About 1 in 5 people who are infected will develop a fever with other symptoms such as headache, body aches, joint pains, vomiting, diarrhea or rash. Most people with this type of West Nile virus disease recover completely, but fatigue and weakness can last for weeks or months.

Severe symptoms in a few people. Less than 1 percent of people who are infected will develop a serious neurologic illness such as encephalitis or meningitis (inflammation of the brain or surrounding tissues).

  • The symptoms of neurologic illness can include headache, high fever, neck stiffness, disorientation, coma, tremors, seizures or paralysis.
  • Serious illness can occur in people of any age. However, people over 60 years of age are at the greatest risk for severe disease. People with certain medical conditions, such as cancer, diabetes, hypertension or kidney disease, or people who have received organ transplants, are at a greater risk for serious illness.
  • Recovery from severe disease may take several weeks or months. Some of the neurologic effects may be permanent.
  • About 10 percent of people who develop neurologic infection due to West Nile virus will die.
  • No vaccine or specific antiviral treatments for West Nile virus infection are available.
  • Over-the-counter pain relievers can be used to reduce fever and relieve some symptoms.
  • In severe cases, patients often need to be hospitalized to receive supportive treatment such as intravenous fluids, pain medication and nursing care.

West Nile virus is most commonly transmitted to humans by mosquitoes.

Additional routes of human infection have also been documented. It is important to note that these methods of transmission represent a very small proportion of cases:

  • Blood transfusions
  • Organ transplants
  • Exposure in a laboratory setting
  • From mother to baby during pregnancy, delivery or breastfeeding

West Nile virus is not transmitted:

  • From person-to-person or from animal-to-person through casual contact. Normal veterinary infection control precautions should be followed when caring for a horse suspected to have this or any viral infection.
  • From handling live or dead infected birds. You should avoid bare-handed contact when handling any dead animal. If you are disposing of a dead bird, use gloves or double plastic bags to place the carcass in a garbage can.
  • Through consuming infected birds or animals. In keeping with overall public health practice, and due to the risk of known food-borne pathogens, always follow procedures for fully cooking meat from either birds or mammals.

The most effective way to avoid West Nile virus disease is to prevent mosquito bites. Be aware of the West Nile virus activity in your area and take action to protect yourself and your family.

  • Use insect repellents when you go outdoors containing DEET, picaridin or IR3535 and oil of lemon eucalyptus.
  • When weather permits, wear long sleeves, long pants and socks when outdoors.
  • Take extra care during dusk and dawn, the peak mosquito biting hours.
  • Install or repair screens on windows and doors to keep mosquitoes outside.
  • Empty standing water from containers such as flowerpots, gutters or buckets.

Frequently Asked Questions

What should I do if I find a dead bird?
The Health Department is no longer testing dead birds for West Nile Virus but rather is focusing the surveillance effort on the mosquito population. Citizens who find a dead bird should place the carcass in a plastic bag and dispose of it in their regular trash, taking care to avoid handling the carcass by using gloves or other means to pick up the carcass. Hands should be thoroughly washed afterwards. West Nile Virus is not transmitted by contact with the carcass and these precautions are appropriate for dealing with any animal carcass.

Can my pet contract West Nile virus?
Although there is some evidence that other animals can contract West Nile virus, horses seem to be most vulnerable. West Nile virus is transmitted through mosquitoes that become infected while feeding on infected birds. Research is continuing on this virus and the impact on other animal populations.

How will I know if I have West Nile virus?
Fortunately, most people who are exposed to this virus will experience no symptoms of illness or they may experience only mild flu-like illness, such as fever, muscle aches, stiffness in the neck, headache or swollen lymph glands. The incubation period typically ranges from 3-15 days. Only in rare cases does this virus cause serious illness. Although this illness can affect people at any age, it tends to be most severe in the elderly, the very young or those with chronic illnesses or weakened immune systems. Persons experiencing severe symptoms should consult their personal physician promptly.

Helpful Links:

The City practices integrated mosquito control with the intent to disrupt the mosquito life cycle in its early stages to eliminate the number of adults and mosquito breeding habitats through proper water drainage. Mosquito control activities are conducted year-round but are increased from April through October, the most active mosquito season in North Texas.

How to Protect Yourself
Follow the Four D's of protection:

  • DRAIN standing water around the home
  • Use insect repellent containing DEET
  • Avoid being outdoors at DUSK and DAWN
  • DRESS to protect yourself with long sleeves and pants