West Nile Virus FAQ
1What is the basic transmission cycle of the West Nile virus?
West Nile virus normally cycles among birds and mosquitoes. The virus circulates in the blood of birds for a few days after infection. Mosquitoes become infected when they feed on infected birds. Infected mosquitoes can then transmit West Nile virus to humans and animals through their bites. The virus is injected from the mosquito’s salivary glands into the blood stream where it can multiply and cause illness.
2What can be done to prevent outbreaks of West Nile encephalitis?
Prevention of West Nile encephalitis and interruption of West Nile virus transmission is most effectively accomplished through integrated vector management programs like those employed by MMCD. MMCD is working closely with the Minnesota Department of Health to detect and control West Nile virus. This includes surveillance for West Nile virus activity in mosquitoes, birds, horses, other animals, and humans. Also important are implementation of appropriate mosquito control measures to reduce mosquito populations and public notification efforts. MMCD provides mosquito control services in the seven county metropolitan area and we work with MDH to keep the public informed of the current West Nile virus situation.
3Is there a vaccine against West Nile encephalitis?
A vaccine for humans is in development and may be available within the next five years. A vaccine for horses is available. Inoculation requires two doses of the vaccine, so it is important to schedule vaccination prior to elevated mosquito activity. Contact your veterinarian for more details.
4What can I do to reduce my risk of becoming infected with West Nile virus?
- Stay indoors at dawn and dusk when most mosquitoes are active.
- Wear long-sleeved shirts and long pants whenever you are outdoors.
- Spray clothing with repellents containing DEET or permethrin.
- Apply insect repellent containing DEET sparingly to exposed skin. Follow the manufacturer’s guidelines for use of repellents. Several DEET repellents which are formulated for use on children are available.
- Ultrasonic devices and vitamin or herbal supplements do not provide effective prevention from mosquito bites.
- Remove any water-holding containers from your property, they can produce mosquitoes.
- If you are a resident of the District, MMCD will recycle your unwanted tires provided they are off the rims.
5What are the symptoms of West Nile encephalitis?
Most infections are mild, symptoms include fever, headache, and body aches, occasionally with a skin rash and swollen lymph glands. More severe infection may be marked by headache, high fever, neck stiffness, stupor, disorientation, tremors, convulsions, muscle weakness, paralysis, coma, and in 10% to 15% of severe cases, death.
6Who is at risk for getting West Nile encephalitis?
All residents of areas where West Nile virus activity has been identified and all visitors to those areas are at risk of contracting West Nile encephalitis. People who are over the age of 50 are at greatest risk of contracting severe illness after exposure to West Nile virus.
7If I think I have symptoms of West Nile encephalitis, what should I do?
Contact your health care provider if you have concerns about your health. If you or your family members develop symptoms such as high fever, confusion, muscle weakness, and severe headaches, you should seek immediate medical attention.
8What are my chances of getting sick from West Nile virus?
A very small percentage of people actually become ill from West Nile virus even in areas where the virus is active. Few mosquitoes actually carry the virus, less than 1% are infected. Fewer than one percent of people bitten by infected mosquitoes develop severe illness. The chances of contracting West Nile encephalitis are extremely small.
9How is West Nile encephalitis treated?
There is no treatment for the viral infection itself. In severe cases, intensive supportive therapy is required. This may include hospitalization, intravenous fluids, airway management, respirator support, prevention of secondary infections, and nursing care.
West Nile and Birds
1What birds can be exposed to West Nile Virus?
Crows and blue jays are particularly susceptible to West Nile virus.
2Does West Nile virus cause illness in birds?
Most birds show little or no affect from infection with West Nile virus. Some bird species, however, do develop severe illness. Mortality rates are high in crows, blue jays, and some birds of prey. West Nile virus may cause death in other species as well, but at lower rates.
3Can I get West Nile virus directly from birds?
There is no evidence to date suggesting that humans can get West Nile virus from touching sick or dead birds. However, it is strongly recommended, for sanitary reasons, that you use protective gloves or a plastic bag when handling any sick, injured, or dead bird.
West Nile and Horses, Dogs, and Cats
1Does West Nile virus affect horses?
Yes. An infection with West Nile virus can result in encephalitis in horses. Most horses infected with West Nile virus recover, but for horses that develop severe symptoms mortality rates have ranged from 30% to 40% in the United States.
2How do the horses become infected with West Nile virus?
The same way humans become infected, by the bite of infectious mosquitoes. The virus is located in the mosquito’s salivary glands. When mosquitoes bite the horse, the virus is injected into its blood system. The virus then multiplies and may cause illness. The mosquitoes become infected when they feed on infected birds or other animals.
3Can I vaccinate my horse against West Nile virus infection?
A West Nile virus vaccine for horses is available. Proper inoculation requires at least two doses of the vaccine, so it is important to schedule vaccination prior to elevated mosquito activity. Contact your veterinarian for more details.
4Can West Nile virus infect dogs or cats?
Dogs and cats can become infected with West Nile virus in the same way as humans, horses, and birds; by the bite of an infectious mosquito. Illness in dogs and cats is extremely rare.
5Can infected dogs or cats be carriers of West Nile virus and transmit the virus to humans or other pets?
West Nile virus is transmitted by infectious mosquitoes. There is no documented evidence of direct transmission of the virus to people from infected animals or to pets from another infected animal.