Doneen Hollingsworth, Secretary of Health



South Dakota Department of Health
Office of Disease Prevention - 605-773-3737 — (1-800-592-1861 in South Dakota only)
Department of Health West Nile Virus Information
This material is provided for informational purposes only and is not a substitute
for medical care. We are not able to answer personal medical questions. Please see your
health care provider concerning appropriate care, treatment or other medical advice.

What is West Nile virus disease?
West Nile virus disease is a mosquito-borne infection that can cause mild flu-like illness or severe encephalitis. Although chances of a person getting encephalitis are small, there are some steps you can take to reduce your risk of being bitten by mosquitoes.

What is encephalitis?
Encephalitis is an infection of the brain. The symptoms include headache, high fever, stiff neck, stupor, disorientation, coma, tremors, convulsions, weakness and paralysis. These symptoms may last several weeks, although neurological effects may be permanent.

Should we stay indoors?
It is not necessary to limit any outdoor activities, unless local officials advise you otherwise. However, you can and should try to reduce your risk of being bitten by mosquitoes. In addition to reducing stagnant water in your yard, make sure all windows and doors have screens, and that all screens are in good repair. If WNV is found in your area:

  • Minimize time spent outdoors between dusk and dawn.
  • Wear shoes, socks, long pants and a long-sleeved shirt when outdoors for long periods of time, or when mosquitoes are most active.
  • Use mosquito repellent containing DEET, Picaridin, oil of lemon eucalyptus, or IR3535, according to directions, when you are outdoors.

Do all mosquitoes transmit disease?
No. Some mosquitoes do not transmit disease. There have been 43 different species of mosquitoes identified in South Dakota. Of these only 9 species are known vectors of WNV. Other species have been associated with WNV in other states.

Where do mosquitoes live and breed?
The mosquito that commonly transmits WNV lays its eggs in stagnant water, both in natural ground pools and in artificial containers. The eggs become larvae that remain in the water until they mature and fly off. Weeds, tall grass and shrubbery provide an outdoor home for adult mosquitoes. They can also enter houses through unscreened windows or doors, or broken screens. Most mosquitoes will breed in discarded tires.

When are mosquitoes most active?
Some mosquitoes are most active between dusk and dawn, when the air is calm. However, others may be present at any time of day, and feed during the daytime and at dusk.

What bird(s) can carry West Nile virus?
Although most birds can be infected with West Nile virus, crows, blue jays, magpies, hawks, owls and eagles are most likely to die from the virus.

Can you get West Nile virus directly from birds?
There is no evidence that a person can get the virus from handling live or dead infected birds. However, avoid bare-handed contact when handling any dead animals and birds. Use gloves or double plastic bags to place the carcass in a garbage can.

Can other animals become infected?
Yes. WNV can make horses very ill. It can also be detected in dogs, cats, bats, chipmunks, raccoons, skunks, squirrels, and domestic rabbits. It is important to remember that animals cannot transmit WNV to people.

How can I protect my family and myself?
Use mosquito repellent containing DEET, Picaridin, oil of lemon eucalyptus, or IR3535, according to directions, when you are outdoors.

To reduce the mosquito population around your home and property, reduce or eliminate all standing water:

  • Remove all discarded tires on your property. Used tires have become an important source of mosquito breeding in the nation.
  • Drill holes in the bottoms of recycling containers that are kept outdoors.
  • Make sure roof gutters drain properly, and clean clogged gutters in the spring and fall.
  • Turn over plastic wading pools and wheelbarrows when not in use.
  • Change the water in birdbaths.
  • Clean vegetation and debris from edges of ponds.
  • Clean and chlorinate swimming pools, outdoor saunas and hot tubs.
  • Drain water from pool covers.
  • Use landscaping to eliminate standing water that collects on your property.

Since bats eat insects should we encourage bats to live on our property to help control mosquitoes?
No. Research has shown that insectivorous bats are selective feeders and mosquitoes make up a very small percent of their diet. They will typically feed on the larger insects. Bats can also harbor and transmit rabies. Bats are not an adequate means in controlling the population of mosquitoes.

Is there a vaccine against West Nile encephalitis?
There is no human vaccine for WNV.

Should people take the West Nile virus vaccine that is licensed for use in horses?
No. This vaccine has not been studied in humans and could be harmful. The effectiveness of this vaccine in preventing West Nile virus infections in horses has yet to be fully evaluated, and its effectiveness in humans is completely unknown. Veterinary vaccines are not manufactured with the same standards required of human vaccines, nor are they required to undergo the extensive field testing required of human vaccines before they are licensed. For these reasons, veterinary vaccines and other veterinary drugs should never be used in humans.

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