West Nile encephalitis, a mosquito-transmitted disease, was first documented in North America during the summer of 1999, when an outbreak occurred in New York City. Since that time, cases of West Nile virus (WNV) have been reported across North America. As of March,2006, there have been 19,665 confirmed human cases of WNV in the United States, 782 of these cases resulted in death. In 2005 alone, there were 105 fatalities.

23,278 cases in horses have been confirmed in the United States. An equine vaccine is available in some states through licensed veterinarians. For more information, click on the links below.

The strain of WNV circulating in the United States causes significant mortality in exotic and native bird species, especially in the American crow (Corvus brachyrhynchos). Dead birds serve as an early warning that the virus may be active in your area, report these to your local health department.

Current North Dakota West Nile Virus Cases

CDC map of West Nile in the United States

Origin of WNV
WNV was first isolated in 1937 in the West Nile province of Uganda, Africa, and can adversely affect humans, birds, and other animals in Africa, Eastern Europe, western Asia, and the Middle East. Epidemics have occurred in Africa, Europe, and the Middle East, most recently in Israel during 2000.

Virus Transmission
WNV is transmitted by infected mosquitoes, primarily of the genus Culex. In Cass County, a species of mosquito called Culex tarsalis is the primary vector of WNV among other diseases. Cx. pipiens, the northern house mosquito, is a common household mosquito and the primary vector of WNV in the Eastern United States.



Mosquitoes become infected after biting infected wild birds that serve as the primary host of the virus. The virus undergoes a reproductive cycle inside the mosquito, in which it must pass through the midgut wall, multiply in many tissues, and accumulate in the salivary glands of the mosquito. Mosquitoes salivate every time they bite, and they are capable of transmitting the virus 10 to 14 days after feeding on an infected bird, so bites after that time are infectious.

Symptoms of West Nile Encephalitis
Body aches
Swollen lymph glands
Body rash

Most humans infected with WNV have no symptoms.
Encephalitis develops in less than 1 percent of infected people, with severe symptoms that include headache, high fever, neck stiffness, disorientation, tremors, convulsions, paralysis, and coma. If you experience these symptoms, contact a physician or hospital immediately. Occasionally, death can occur. The elderly are most at risk of death due to encephalitis.

Mosquito Prevention and Control - WHAT YOU CAN DO


The primary defense anyone can utilize is to wear an EPA approved repellent- most commonly those containing DEET. Always remove any standing water from your property and make sure your door and window screens are secure and without holes.




The American Mosquito Control Association (AMCA) has published their position on mosquito traps and this can be viewed at: mosquito.org

For more information about WNV and mosquito control recommendations visit the Center for Disease Control Web Site at www.cdc.gov/ncidod/dvbid/westnile/index.htm

North Dakota Department of Health – www.health.state.nd.us/


North Dakota Department of Agriculture – www.agdepartment.com

USDA Animal and Plant Inspection Service – www.aphis.usda.gov/

USGS West Nile Virus Maps - http://cindi.usgs.gov/hazard/event/west_nile/west_nile.html

Real Life Stories from West Nile Virus Survivors - http://www.westnilesurvivor.com/faq.html

Works Cited: http://www.cdc.gov/ncidod/dvbid/westnile/qa/overview.htm


 WNV in North Dakota