Minnesota's first human case this year of West Nile virus has been confirmed, the state Health Department said this week.
The case involved a man from St. Louis County who developed West Nile encephalitis and meningitis in late May after traveling to south central Minnesota. He was hospitalized and is recovering, state health officials said.
West Nile virus is transmitted through the bite of infected mosquitoes. Health officials urge Minnesotans to protect themselves from mosquito bites from now through the autumn frost.
Sporadic disease sometimes shows up early in the season, such as this first case of 2012, said Dave Neitzel, a state Health Department epidemiologist specializing in mosquito-borne diseases.
But the mosquito species that transmits West Nile virus to humans "is most abundant in July and August," he said. "Anyone not already using repellents should begin doing so now to prevent this severe disease."
Most people who get West Nile virus are mildly ill or have minimal symptoms, but a small percentage of individuals can develop central nervous system disease and become severely ill. About 10 percent of those with the worst form of the virus die from the disease and survivors may have long-term neurological problems.
The risk is greatest for older adults and individuals with weakened immune systems. "They need to be especially diligent about protecting themselves from mosquitoes," Neitzel said.
The risk also is higher in western and central Minnesota counties, where the habitat consists of open agricultural land favored by Culex tarsalis mosquitoes, the species of mosquito that is the primary carrier in Minnesota of the West Nile virus.
Symptoms of West Nile virus usually begin five to 15 days after being bitten and can include headache, high fever, rash, muscle weakness, stiff neck, disorientation, convulsions, paralysis and coma.
Health officials recommend using mosquito repellents and minimizing outdoor time at dusk and dawn, when mosquitoes carrying the West Nile virus are feeding most actively.
Repellents containing DEET are considered among the safest and most effective. They can be applied directly to the skin. Repellents that contain permethrin are applied to clothing. Alternatives include repellents containing picaridin, oil of lemon eucalyptus or IR3535.
Since West Nile virus was first found in Minnesota in 2002, there have been 465 cases of West Nile virus disease, including 15 deaths.