Michigan Reports Case Of LaCrosse Virus

July 12, 2007

The Michigan Department of Community Health (MDCH) has positively identified the state's first case of LaCrosse virus for 2007 in a Wayne County woman. The woman first showed symptoms of the LaCrosse virus in early June, was hospitalized, and has since been discharged, officials said Thursday.

Like West Nile Virus (WNV), LaCrosse virus is a mosquito-borne viral infection that can cause encephalitis in humans. Children under the age of 16 are more susceptible to illness following infection with LaCrosse virus. Mosquitoes that transmit LaCrosse virus are typically found in woodland habitats, but they can breed in containers, and also have been associated with scrap tires.

Michigan reported 11 cases of LaCrosse virus in 2002-the first year health care professionals were testing in heavy volume for WNV throughout the state. Michigan had no cases of LaCrosse in 2003 and 2005, one case in 2004, and two cases reported in 2006.

"The detection of LaCrosse virus in Michigan re-emphasizes the importance of efforts to educate the public about how to reduce their risk of mosquito-borne infection," said Dr. Gregory Holzman, State Chief Medical Executive. "This case reminds us that we need to take precautions to protect ourselves and our families from mosquitoes and the diseases they carry."

Even though WNV has not yet been identified in birds or humans in Michigan this year, it is presumed to be present in the state. The virus has been responsible for human illnesses in Michigan every year since 2002. While federal funds to support WNV surveillance are decreasing, state agencies continue to offer WNV testing in birds and mosquitoes for communities conducting mosquito control activities.

Dead crows, blue jays, and ravens remain a sensitive indicator of the presence of WNV in a community. People can report dead bird sightings on the state's WNV web site at www.michigan.gov/westnilevirus.

Holzman said about one-in-five WNV 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 over the age of 50 are more susceptible to severe WNV disease symptoms. Physicians are urged to test patients for WNV and other mosquito-borne viruses 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 active ingredients such as DEET or Picaridin 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).

For more information on LaCrosse and WNV in Michigan, please visit www.michigan.gov/emergingdiseases.