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CDC facts on West Nile Virus
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• West Nile virus can infect humans, birds, mosquitoes, horses and other animals, according to data from the Center for Disease Control.

• The virus is common in Africa, Eastern Europe, West Asia and the Middle East. The U.S. strain, first documented in 1999, is most closely related genetically to strains in the Middle East.

• Mosquitoes generally become infected when they feed on infected birds, which may circulate the virus in their blood for a few days. They in turn pass the virus along when feeding.

• The center estimates that 20 percent of people who become infected will develop mild, flu-like symptoms, including fever, headache, body aches, possibly a skin rash on the trunk of the body and swollen lymph glands. Mild cases typically last a few days.

• A severe infection causes inflammation of the brain and the membrane surrounding it, producing headache, high fever, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness and paralysis. Symptoms may last several weeks, although neurological effects may be permanent. The center estimates that one in 150 persons infected with the virus will develop the more severe form.

• Incubation takes from three to 14 days.

• Game hunters may be more at risk because of outdoor exposure. No evidence exists that eating infected birds or animals transmits the virus to humans. However, people should always cook game fully, and hunters should wear gloves when handling and cleaning animals to prevent blood exposure. The extent to which the virus may be present in wild game is unknown.

• For information on local area risks, hunters should check with their local department of wildlife and state epidemiologists or the US Geological Survey (USGS) National Wildlife Health Center in Madison, Wis., (608) 270-2400.

• Documented evidence does not support transmission of the virus between horses, but infected horses should be isolated from mosquitoes if possible. Data suggest that most horses recover from the virus when treated.

• Dogs and cats do not appear susceptible to serious illness from the virus. It is possible that these animals could contract the infection by eating dead infected animals and birds, but this is unproven.

Source: Center for Disease Control

Compiled by Nancy L. Torner, journalist with the Center for Rural and Regional Studies at Southwest State University in Marshall, Minn.; tornern@southwest.msus.edu; (507) 537-6030.

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Last updated: February 1, 2006