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Frequently Asked Questions About West Nile Virus
-
What
is West Nile Virus (WNV)
-
How
can I be exposed to WNV?
-
Do
all mosquitoes carry WNV?
- Can WNV make me sick?
-
Reduce
mosquito breeding habitat
- How can I reduce mosquito bites?
- How is Public Health - Madison and Dane County Responding?
- What do I do with dead birds in my yard?
- Map: Mosquito Larvae Monitoring Results - 2005 (PDF)
WEST NILE VIRUS
West Nile Virus (WNV) was first identified in Dane County in 2001, in a dead crow. Multiple WNV positive birds have been found in Dane County every year since then. For this reason, the emergence of the mosquito-borne West Nile Virus (WNV) in Wisconsin, and specifically in Dane County, has created the need for a public health response. The following is information about WNV, the illness that may result, and Dane County's public health response.
Click here for state-wide and national public health information on West Nile Virus.
West Nile Virus is a virus that was first identified in Uganda in 1937. This virus was first identified in the United States in 1999 during an outbreak in New York. Since that time, the virus has been found in mosquitoes, birds, horses, and humans throughout the United States.
People may be exposed to WNV when an infected mosquito bites them. However, only a small percentage of mosquitoes are expected to carry the virus so the risk of being infected with WNV from any single mosquito bite is very small. For a mosquito to become infected with the virus, it must bite an infected bird.
No. Monitoring data in the United States have indicated that mosquitoes in the Culex group are most often infected with WNV. This is significant because most of the nuisance mosquitoes in Madison belong to the Aedes group, which are less likely to carry the West Nile Virus. Culex mosquitoes found in the Madison area (usually Culex pipens or Culex restuans) are considered to be evening and nighttime biters and commonly breed in stagnant or polluted water.
Most of the time, people infected with WNV will have no symptoms or will develop a mild illness that includes fever. In severe cases, encephalitis may develop. The Centers for Disease Control and Prevention (CDC) reports that less than 1% of persons that get infected will develop severe illness. Serious illness resulting from WNV can happen at any age; however, most cases of serious illness have occurred in persons greater than 50 years of age.
WHAT CAN I DO TO PREVENT EXPOSURE TO WNV?
Reduce mosquito breeding sites. The Culex mosquitoes found in Madison prefer to breed in stagnant or polluted water. For this reason, eliminating standing water from your property may have a significant impact on reducing the number of Culex and other mosquitoes. Eliminate standing water around your home and neighborhood by:
- Disposing of used tires.
- Cleaning rain gutters.
- Changing water in bird-baths and child wading pools every 3-4 days.
- Keeping swimming pools chlorinated.
- Keeping any containers from collecting rainwater (i.e. wheel barrows, flower pots, buckets, swimming pool covers, etc).
Click here to see a video showing these types of sources.
Reduce the number of mosquito bites you receive. While mosquito bites cannot be eliminated completely, they can be reduced by simple behavior changes when out amongst the mosquitoes. Some of these include:
- Apply insect repellent sparingly
to exposed skin. Effective repellents include products containing:
- 6 - 30% DEET (N,N-diethyl-meta-toluamide). Products with 6% DEET are effective for about 2 hours while products with 25 – 30% DEET are effective for 8 hours. DEET in high concentrations (greater than 30%) provides no additional protection.
- Picaridin
- Oil of lemon eucalyptus
- IR3535
Products containing picaridin, oil of lemon euclayptus, or IR3535 are effective for shorter periods of time than products containing higher concentrations of DEET.
- Don't let children apply their own repellant and avoid applying repellent to the hands of children.
- Whenever you use an insecticide or insect repellent, be sure to read and follow the manufacturer's DIRECTIONS FOR USE, as printed on the product.
- Spray clothing with repellents containing permethrin or DEET since mosquitoes may bite through thin clothing.
- Wear long-sleeved shirts and long pants when outdoors.
- When the wind is calm or low, sit in front of a fan to reduce the ability of mosquitoes to fly and land on you to bite.
- Install or repair window and door screens.
- Note: Vitamin B and "ultrasonic" devices are NOT effective in preventing mosquito bites.
HOW IS PUBLIC HEALTH - MADISON AND DANE COUNTY RESPONDING?
The Public Health Department is
focusing on education, surveillance, and limited treatment of mosquito
breeding habitat in the Madison Metropolitan Area to address the concern
about WNV in our area. The Madison Metropolitan Area includes the City
and Town of Madison, Middleton, Monona, Maple Bluff, Shorewood Hills,
Sun Prairie, and the University of Wisconsin.
Surveillance
Public Health collects information on dead crows and blue jays to measure the impact of WNV on the bird population from year to year. At this time, this is our best measure of the level of this disease in Madison and Dane County and helps the Department determine the risk of humans to become ill with WNV from May through October.
Dane County residents who find a sick or dead crow or blue jay should call 1-800-433-1610 to report the bird. In Dane County, Animal Services Officers will be picking up some sick blue jays and crows and submitting them for WNV testing. Testing for WNV in sick crows and blue jays ends after two birds test positive for WNV.
Public Health staff also collect and monitor information on WNV infection in humans throughout the season. Infections in humans are monitored through lab testing and reports from healthcare providers. Click here for the 2007 West Nile Virus Surveillance Report in Dane County. (PDF)
Treatment
of Mosquito Breeding Areas
In 2008, Public Health will continue monitoring for mosquito breeding and treating sources of water on public land that are found to produce high numbers of mosquitoes known to carry and transmit WNV (primarily Culex species). The primary objective of this treatment will be to limit the build up of WNV infection in the bird population. This treatment protects human health by reducing the amount of virus in the environment. The Department will continue to trap adult mosquitoes to measure population levels. Click here for the 2007 Mosquito Monitoring and Control Report for the Metropolitan Area. (PDF 16,827KB) For question about mosquito monitoring and control, contact jhausbeck@publichealthmdc.com.
WHAT
DO I DO WITH DEAD BIRDS IN MY YARDS?
After reporting a dead crow or blue jay, the bird can be picked up and disposed of in the household garbage by placing a plastic bag over your hand, picking up the bird with the covered hand, and pulling the bag around the bird. While West Nile Virus is not easily transmitted to humans by handling an infected bird, it is prudent to avoid touching sick or dead birds with bare hands. Double bagging and sealing or tightly tying the bag shut should help prevent odors in the garbage. In the City of Madison, the dead bird can be placed on the terrace and you can call City Engineering Division at 266-4430 to request that the animal be picked up.
If the bird is still alive but obviously sick, call 255-2345 and request an Animal Services Officer response.
If you have further questions about West Nile Virus in Madison and Dane County, call Public Health for Madison and Dane County at (608) 266-4821 or email at akita@publichealthmdc.com.