Michigan's first West Nile virus case of the year was confirmed Friday in a bird found in Muskegon County.
The crow was collected earlier this month and tested positive for the virus at Michigan State University's Diagnostic Center for Population and Animal Health.
Health experts are not surprised that West Nile has resurfaced in the state. The Michigan Department of Community Health says cases of the mosquito-borne virus can be expected in birds, horses, other animals and humans in 2006.
But officials say the extent of the virus can't be predicted.
"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," Dean Sienko, the state's acting chief medical executive, said in a statement. "Preventing exposure to mosquitoes in the months ahead will be important."
Most people bitten by a West Nile-infected mosquito show no symptoms. But if they do become sick, symptoms typically show from three days to two weeks afterward.
About one in five people infected with the virus will have a mild illness with fever, headache and body aches, sometimes with a skin rash and swollen lymph glands.
Severe cases may result in encephalitis, meningitis or death.
Michigan had 62 reported human cases and four deaths from West Nile in 2005. There also were 13 cases involving horses and 131 involving birds.