Michigan's First 2007 WNV Human Case Detected

August 2, 2007

LANSING - Researchers at the Michigan Department of Community Health (MDCH) public health laboratory have today positively identified the state's first human case of West Nile Virus (WNV) for 2007. A 25-year-old Oakland County woman was hospitalized in mid-July with symptoms associated with the disease.

"Because we cannot predict the impact WNV will have on Michigan again this year, it is crucial that citizens are aware of the potential risk of WNV infection," said Janet Olszewski, MDCH Director. "Communities should use surveillance information to target intervention and prevention strategies in areas where WNV activity has been detected."

Late spring typically signals the beginning of the season for mosquito-borne diseases such as WNV in Michigan. Surveillance activities for WNV continue this year as a cooperative partnership involving the Michigan Departments of Agriculture, Community Health, Environmental Quality and Natural Resources, Michigan State University, and local health departments throughout the state.

All agencies are integral parts of Michigan's WNV surveillance, prevention, and response strategies. Mosquitoes most likely to transmit WNV to humans lay eggs in small collections of stagnant water.

Adults can hatch in as short as 10 days time in the warmest months of the summer. Mosquitoes become infected with WNV after feeding on sick birds carrying the virus. Within 10 to 14 days, the mosquito can transmit the virus to humans.

"It is important that Michigan residents take the necessary precautions to prevent exposure to mosquitoes until our first frost of the season," said Dr. Gregory Holzman, MDCH Chief Medical Executive. "Since West Nile virus is spread to humans and horses almost exclusively through the bite of an infected mosquito, people need to take measures that reduce the chance of receiving mosquito bites."

Most people bitten by a WNV infected mosquito show no symptoms of illness. However, some become sick three to 15 days after exposure.

Holzman said about one-in-five infected persons will have mild illness with fever, and about one in 150 infected people will become severely ill. Symptoms of encephalitis (inflammation of the brain) and meningitis (inflammation of the spinal cord and brain linings) include stiff neck, stupor, disorientation, coma, tremors, muscle weakness, convulsions and paralysis. 

Persons aged 55 and older are more susceptible to severe WNV disease symptoms. Physicians are urged to test patients for WNV if they present with fever and signs of meningitis or encephalitis, or sudden painless paralysis in the absence of stroke in the summer months. Blood donor screening for WNV is expected to continue in 2007.

Michigan residents are encouraged to:

- Maintain window and door screening to help keep mosquitoes out of buildings.

- Drain puddles in the yard, emptying water from mosquito breeding sites such as buckets, troughs, barrels, old tires or similar sites where mosquitoes lay eggs.

- Avoid being outdoors when mosquitoes are most active (dawn and dusk)

- Wear light colored long-sleeved shirts and long pants when outdoors.

- Apply insect repellants that contain the active ingredient DEET to exposed skin or clothing, always following the manufacturer's directions for use. (Avoid applying repellent to children less than 2 years of age, and to the hands of older children because repellents may be transferred to the eyes or mouth potentially causing irritation or adverse health effects).

Collection of information on the sightings of sick and dead wild birds and mammals is necessary for monitoring the risk of WNV to humans, wildlife and domestic animals. For rapid reporting of a sighting, please use the web-based reporting form by visiting the state's website at www.michigan.gov/westnilevirus.

For those without Internet access, you may use your local library to access the Internet or call the statewide toll-free number at: 1-888-668-0869 for updated information about WNV.