Polk case raises West Nile risk

By Bob Williams | The Daily Journal

Published Tuesday, July 17, 2007

Residents of west central Minnesota are at risk for West Nile virus, local officials and the Minnesota Department of Health said after the first case was reported in Polk County late last week.

Polk County is southeast of Grand Froks. The woman developed meningitis in late June after becoming infected with the virus. She is recovering.

“A majority of West Nile virus human cases will be in central and western Minnesota, as that is where the Culex tarsalis mosquito is most prevalent,” said JoAnn Bowman, infection control coordinator at Lake Region Healthcare.

The mosquito that most often carries the virus is most abundant in open, agricultural areas and the coming two months are the time of year the pest is prevalent.

“Mid-July through September is the time of year when you’re most likely to be bitten by an infected mosquito,” said David Neitzel, an epidemiologist with the Minnesota Department of Health.

“We’re particularly concerned about agricultural workers,” University of Minnesota Extension Safety and Healthy Specialist John Shutske said. “Or others working outside who might not think about using repellents.”

Bowman said that most people exposed to the West Nile virus have few, if any, symptoms. However, those with weakened immune systems, especially the elderly, are vulnerable to severe disease. Those bitten by an infection mosquito usually show symptoms two to 15 days later.

The most severe form of West Nile virus is encephalitis. Most of the severe cases of West Nile encephalitis begin with a sudden onset of fever, headache, stiff neck and possibly vomiting. The patient may become confused and have other mental status changes. Reflexes next will be altered and this can progress to convulsions and coma.

As many as 10 percent of the elderly with severe encephalitis may die. The patients who survive severe West Nile encephalitis often face a long recovery that may last a year or longer. Some may have permanent neurological problems, such as weakness, difficulty walking, headaches and even permanent hearing loss. Fewer than one out of every 150 people who become infected will become severely ill with encephalitis, an inflammation of the brain.

The MDH recommends using mosquito repellent with DEET when outdoors. Wear long pants and long sleeves when outside and exposure is likely. Avoid being outside during hours when mosquitoes are most active, the early morning and late evening. Last year, 65 cases were reported in Minnesota, including 3 deaths.

Information on West Nile and other forms of mosquito-related encephalitis are available on the MDH Web site at www.health.state.mn.us. People who have questions about West Nile virus can also call MDH at 651-201-5414 in the Twin Cities area, or 1-877-676-5414 in greater Minnesota, between 8 a.m. and 4:30 p.m., Monday through Friday.

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