Below are answers to frequently asked questions about West Nile virus received by the Texas Department of State Health Services (DSHS). Answers to more than 50 frequently asked questions received by the national Centers for Disease Control and Prevention can be found at http://www.cdc.gov/westnile/faq/index.html.
Q. How many human cases have there been in the United States? How many deaths?
A. Between 1999 and 2012, 37,088 cases and 1,549 deaths were reported to CDC. For the latest up-to-date information, go to http://www.cdc.gov/westnile/statsMaps/.
Q. How many human cases have there been in Texas? How many deaths?
A. Between 2002 and 2012, there were 4,070 cases and 229 deaths reported to CDC. For the latest up-to-date information on human cases in Texas, see the DSHS West Nile Virus home page at http://www.dshs.state.tx.us/idcu/disease/arboviral/westNile/.
Q. What is the risk of someone becoming ill with West Nile virus?
A. The risk is very low. Even in areas where the virus is circulating, very few mosquitoes are infected with the virus. Even if the mosquito is infected, less than 1% of people who get bitten and become infected will get severely ill. The chances you will become severely ill from any one mosquito bite are extremely small.
Q. Where in Texas has the virus been found?
A. West Nile Virus has been detected in most counties in Texas. For the most up-to-date information, go to http://www.dshs.state.tx.us/idcu/disease/arboviral/westnile/.
Q. Where does the virus live?
A. Certain types of mosquitos infect birds with the virus. The virus multiplies in the birds which then become a source of the virus for other mosquitos when they feed on infected birds. The infected mosquitoes can also transmit West Nile virus to humans and animals while biting to take blood. The virus is located in their salivary glands and, during blood feeding, the virus can be injected into the animal or human, where it can multiply, possibly causing illness in the animal or human.
Q. Can humans get West Nile virus from handling dead birds?
A. No. West Nile virus is spread to humans mainly through the bite from an infected mosquito. There is no proof that West Nile virus can be spread from person to person or from animal to person.
Q. Can dogs, cats and other pets get West Nile virus?
A. Yes. But they rarely, if ever, get sick. No cases of West Nile disease have been confirmed in dogs and cats. The virus can infect many species of animals, but few actually get the disease. Most infections have been identified in birds, but West Nile virus has been shown to infect dogs, cats, horses, and domestic rabbits, as well as bats, chipmunks, skunks, and squirrels.
Q. Is there a vaccine for dogs and cats?
Q. Is DSHS doing spraying around the state to kill mosquitoes?
A. No. Vector control is up to the Mosquito Control Districts and local health departments. Mosquito control is best performed using the Integrated Mosquito Management (IMM) concept. IMM develops pest management systems that are practical and effective to protect human health and the environment. Mosquito control can be divided into two areas of responsibility, individual and public. Public spraying to control mosquitoes is only one of many pest control methods used for effective long-term mosquito control. The reduction, elimination, or treatment of mosquito breeding areas is the best and most cost-effective technique for mosquito control. The most important things you and the citizens of your community can do to reduce the risk of exposure to West Nile virus are to eliminate mosquito-breeding areas in your environment and limit your exposure to feeding mosquitoes. Many female mosquitoes can lay 100-300 eggs on the surface of fresh or stagnant water every third night during its life span. Here are some simple things you can do to eliminate potential mosquito breeding sites in your environment:
- Do not allow water to accumulate in the saucers of flowerpots, cemetery urns, or in pet dishes for more than 2 days.
- Get rid of tin cans, old tires, buckets, unused plastic swimming pools or other containers that collect and hold water.
- Clean debris from rain gutters, remove standing water from flat roofs, and repair leaks around faucets and air conditioners.
- Change the water in birdbaths and wading pools at least once a week.
- Fill or drain puddles, ditches and swampy areas.
- Check for trapped water in plastic or canvas tarps used to cover boats or pools, and arrange the tarp to drain the water.
- If ditches do not flow and contain stagnant water for a week or longer, report this problem to a mosquito control district or public health office.
Q. In addition to being infected by West Nile virus, what else can cause bird "die-offs"?
A. Chemical spills, pesticides, drought, severe weather, and other diseases can cause die-offs in birds. To report a die-off of birds, contact the Texas Parks and Wildlife Department's Kills and Spills Team (KAST) at (512) 389-4848. For additional information, go to http://www.tpwd.state.tx.us/landwater/water/environconcerns/kills_and_spills/
Note: The Texas Department of State Health Services (DSHS) does not test birds for West Nile virus. However, some local jurisdictions take citizen reports of dead birds and may also do testing. Please do not contact DSHS if you find a dead bird. You may contact your city or county government to find out if they are taking reports from citizens or testing birds for WNV. If you wish to dispose of a bird carcass, wear gloves and dispose of it in the garbage. As a reminder, whenever you handle an animal, you should wash your hands.
Q. What's an arbovirus?
A. Any of various RNA viruses which are the causative agents of encephalitis, yellow fever, and dengue and which are transmitted chiefly by arthropods, such as insects.
Q. What kind of laboratory tests are done to identify the West Nile virus?
A. Various tests can be done. The type of test will vary among mosquitoes, humans, and horses. The type of test also depends on the kind of samples available (blood serum, cerebrospinal fluid, brain tissue, etc.). Samples may be tested to find antibodies to West Nile virus, or there may be an attempt to isolate virus particles from the sample. Tests that can be done include Hemagglutination-Inhibition, IgM-Capture, Plaque-Reduction Neutralization, virus isolation, and PCR. More details are available in the Response Guide at http://www.dshs.state.tx.us/idcu/disease/arboviral/westNile/.
Q. Is there a human vaccine?
A. No. There is no indication that a human vaccine will be available in the near future.
Q. Can a human get the virus twice?
A. We don't think so. It is assumed that a person would develop a natural immunity to future infection by the virus, and that this immunity would be life-long. However, this immunity may wane in later years.
Q. Do the construction of purple martin houses and bat houses near homes help prevent West Nile virus because those animals eat mosquitoes?
A. While it is true that certain types of birds and bats eat mosquitoes, putting up bird and bat houses on your property will not necessarily help prevent the transmission of West Nile virus. Several agencies have tried to control mosquitoes by using birds, bats, dragonflies and frogs. However, according to the American Mosquito Control Association, there is no proof that bats, purple martins, or other animals that eat insects are able to eat enough adult mosquitoes to make a difference. One reason for this is because purple martins fly and eat during the day and most mosquitoes are active at night. In addition, most bats eat June bugs and moths, but do not eat mosquitoes. Also, bats can transmit the rabies virus and encouraging them to live in your yard could pose a health risk to your family and neighbors.A. While it is true that certain types of birds and bats eat mosquitoes, putting up bird and bat houses on your property will not necessarily help prevent the transmission of West Nile virus. Several agencies have tried to control mosquitoes by using birds, bats, dragonflies and frogs. However, according to the American Mosquito Control Association, there is no proof that bats, purple martins, or other animals that eat insects are able to eat enough adult mosquitoes to make a difference. One reason for this is because purple martins fly and eat during the day and most mosquitoes are active at night. In addition, most bats eat June bugs and moths, but do not eat mosquitoes. Also, bats can transmit the rabies virus and encouraging them to live in your yard could pose a health risk to your family and neighbors.
Q. Are “bug zappers” effective in reducing human exposure to West Nile virus?
A. Studies show that bug zappers actually attract mosquitoes into your yard. In addition, most insects killed by bug zappers include moths, beetles and other harmless bugs, not mosquitoes. Mosquito control products are big business. Americans have invested billions of dollars in zappers, repellers, and other products that claim they will keep pesky mosquitoes from biting. The claimed merits of the product are rarely backed with scientific testing. All products should be thoroughly researched before you purchase them. Your best bet would be to use a proven method for keeping your home and property mosquito-free.
Q. Who is responsible for draining mosquito breeding habitat on private property in Texas?
A. In Texas, some city and county governmental agencies have programs for mosquito control. Very often, it is the responsibility of the property owner to address these issues to prevent the creation of a nuisance or public health threat. For advice or assistance with mosquito control on or around your property, check with your local division of health officials to see if your community has a mosquito control district or locally managed mosquito control program.