Minnesota reports its first West Nile virus case this year
The first human case of West Nile virus (WNV) disease in a Minnesota resident in 2012 has been confirmed, according to a statement by the Minnesota Department of Health (MDH) today.
The state's first laboratory-confirmed WNV case of the year is a St. Louis County man who fell ill and was hospitalized with West Nile encephalitis and meningitis in May after traveling to south-central Minnesota. Fortunately, he is recovering.
Minnesotans can protect themselves from the potentially life-threatening WNV by regularly using mosquito repellents and taking other precautions such as minimizing outdoor activities at dusk and dawn, prime feeding times for WNV-carrying mosquitoes, according to MDH officials. Another precaution is wearing long sleeves and pants when spending time in areas with many mosquitoes.
Repellents containing DEET (up to 30 percent concentration) can provide long-lasting protection against bites. Permethrin, a strong repellent, can be worn on the clothes rather than the skin and will kill mosquitoes on contact. Effective alternatives to these include repellents containing picaridin, oil of lemon eucalyptus, or IR3535.
The highest risk for WNV is from mid-summer through early autumn, according to David Neitzel, an MDH epidemiologist who specializes in diseases carried by mosquitoes.
"Sporadic early-season cases can occur, such as this first 2012 case," Neitzel said. "However, the species of mosquito that transmits the virus to humans is most abundant in July and August. Anyone not using repellents should begin doing so now to prevent this severe disease."
Approximately one in 150 people bitten by WNV-infected mosquitoes will develop central nervous system disease (encephalitis or meningitis). Roughly 10 percent of people with this severe form of the infection die from the illness, and many survivors will suffer from long-term nervous system problems.
However, most people bitten by infected mosquitoes develop West Nile fever, the less serious form of the disease, or fight off the virus without any symptoms. But for those who do become very ill, the disease can be devastating.
"Each case is one too many, and the disease can be a huge burden for patients and their families," Neitzel said. "WNV infection can lead to lengthy hospitalization or even death, and some survivors do not fully recover for many months after becoming ill."
Here in Minnesota, it's important for everyone to take all the necessary precautions. Illness from WNV can occur throughout the entire state, and among all age groups. However, WNV risk is greatest in Minnesota's western and central counties, which typically have the greatest number of Culex tarsalis mosquitoes, the primary mosquito carrier of the virus in this state.
The elderly and people with weakened immune systems face the highest risk of developing severe or fatal forms of infection, and should be especially diligent about protecting themselves.
Symptoms of WNV disease usually begin three to 15 days after being bitten and can include headache, high fever, rash, muscle weakness, stiff neck, disorientation, convulsions, paralysis and coma.
Since WNV was first found in Minnesota in 2002, 465 cases (including 15 fatalities) of WNV disease have been reported to MDH.
Information on WNV can be found at the MDH website. Further information on repellents can be found on the CDC website. Or, for questions about WNV, call the MDH at (651) 201-5414 or (877) 676-5414 (outstate) between 8 a.m. and 4:30 p.m. Monday through Friday.
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