West Nile Virus Frequently Asked Questions

With West Nile virus continuing to spread in North Texas, we asked health officials to answer some questions from NBC 5 reporters and viewers.

What is West Nile Virus?
West Nile virus (WNV) is a potentially serious viral infection that can cause flu-like symptoms and exacerbate underlying health conditions. The neuroinvasive form of the virus is more dangerous and has been known to lead to death.

How is it spread?
Mosquitoes infected with the virus bite humans and other animals. Other rare methods of transmission include blood transfusions or passing from pregnant mother to a child still in the womb.

Mosquitoes are infected with the virus by biting birds that have previously been infected.

How do I know I'm infected?
According to the CDC, about 80 percent of patients infected with West Nile virus never show symptoms (see below for list of symptoms). Health officials say if there are no symptoms, there is no need to worry. If you do begin to have symptoms, contact your health care professional.

What are the symptoms of the virus?
Most people bitten by a West Nile virus-infected mosquito will not show any symptoms. Symptoms, if they appear, are fever, headache, nausea, body aches, swollen lymph nodes and skin rashes.

Fewer than one percent of those infected with West Nile virus experience the serious form of the illness. Serious symptoms include high fever, severe headache, neck stiffness, disorientation, tremors or convulsions, vision loss, muscle weakness and numbness or paralysis.

Who is most susceptible to the virus?
Patients with underlying health conditions are in the most danger from West Nile virus, as the disease causes more strain on the immune system. Patients older than 50 are more likely to develop serious symptoms if infected. Residents who have the most outside exposure are most likely to be infected.

How many cases have been found in North Texas?
NBC 5 is keeping a page updated with the latest numbers of human cases, deaths and areas where the virus was detected. Click here to visit that page. The information listed comes from county health officials and may be different from numbers reported by state or federal health officials.

What can residents do to defend against mosquitoes?
The Centers for Disease Control and Prevention states: "the easiest and best way to avoid WNV is to prevent mosquito bites.

• When you are outdoors, use insect repellent containing an EPA-registered active ingredient. Follow the directions on the package.
• Many mosquitoes are most active at dusk and dawn. Be sure to use insect repellent and wear long sleeves and pants at these times or consider staying indoors during these hours.
• Make sure you have good screens on your windows and doors to keep mosquitoes out.
• Get rid of mosquito breeding sites by emptying standing water from flower pots, buckets and barrels. Change the water in pet dishes and replace the water in bird baths weekly. Drill holes in tire swings so water drains out. Keep children's wading pools empty and on their sides when they aren't being used."

What are cities doing to control mosquito population?
Various cities have established different plans to control their mosquito populations. Ground spraying for mosquitoes has been used in many cities, including Dallas and Fort Worth, to help control the population. Cities have also been offering "mosquito dunks" for residents to place in standing water, which should help control the breeding grounds. Aerial spraying has been recommended for Dallas County because of the number of cases in the area.

What's in these mosquito sprays?
Personal insect repellent, including mosquito sprays, have a variety of ingredients and can have different amounts of active insecticides depending on the formula. The CDC has a web page detailing many elements found in personal insect sprays.

Ground spraying and aerial spraying uses other chemical compounds, including synthetic pyrethroid, to paralyze flying insects. The CDC says these substances pose little risk to mammals at the concentrations used in neighborhood spraying. The Environmental Protective Agency has approved the chemicals being used for ground and aerial spraying.

The product used by Dallas County for their aerial spraying is called Duet. A document containing answers to many frequently asked questions about the product can be found by clicking this link.

How can I protect animals from West Nile virus?
Many viewers wondered about protecting their pets from West Nile virus. Parkland doctors say most animals are not as susceptible to West Nile virus and that the risk of infection is minimal. A vaccine for horses is available and is recommended by vets.

What is the contact information if I have adverse effects to the spraying?
Contact the North Texas Poison Center at 1-800-222-1222 if you have any adverse effects to ground or aerial spraying.

“Our poison center responds to calls 24 hours a day, seven days a week in order to help those who have been exposed to toxic substances and we’re fully prepared to answer questions about the aerial spraying in Dallas County,” said Mike Yudizky, public health education manager at the North Texas Poison Center. “We encourage people to do all they can to protect themselves, such as staying indoors during the time aerial spraying will occur.”

How can I protect animals from adverse effects to the spraying?
Though officials recommend bringing pets inside during known spraying times to minimize exposure, information from the companies that make the substances, federal and state health officials, and local authorities say the spraying pose little risk to mammals at the concentrations used in neighborhood spraying, either by air or by ground.

Why is/isn't my city spraying for mosquitoes?
Each city in North Texas is making its own decision about spraying for mosquitoes. Dallas County has recommended a course of action for cities within its area, but the decision to spray, how to spray and what area to cover is up to city leaders.

Due to the large number of individual cities in our viewing area, we recommend you check your city's local website for the latest information on mosquito control plans, West Nile information, and for potential public meetings to discuss what each city is planning.

Is there a vaccine for West Nile virus?
Researchers at the University of Oklahoma are currently working on creating a vaccine for humans, however it may be years away from availability if testing is successful. A vaccine for horses is available and is recommended by vets.

Sources: Centers for Disease Control and Prevention | Dallas County Health and Human Services | Parkland Hospital | North Texas Poison Center