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Doing battle with West Nile virus
by Cara Hetland, Minnesota Public Radio
August 28, 2003

This map shows West Nile virus cases reported to the CDC as of Aug. 27, 2003. The blue indicates cases in birds and animals, the cross-hatch indicates human cases. (Map courtesy of CDC)

South Dakota Gov. Mike Rounds wants everyone in his state to prepare for battle. The enemy is mosquitoes, which are spreading West Nile virus. Four people have died from the West Nile virus in the last week. More than 250 human cases have been reported in South Dakota this summer. Rounds says the next three weeks is the peak season for mosquitoes and West Nile.

Sioux Falls, S.D. — West Nile virus was first detected in the United States in 1999. Since then the disease has spread to 44 states and the District of Columbia. The disease arrived in the Midwest last summer. This year, Colorado, Nebraska and South Dakota have the most reported human cases of West Nile virus. Minnesota has 15 human cases so far this season.

Experts say from now until mid-September, the mosquitoes carrying the disease are most active. The species is called Culex Tarsalis. It's not your typical mosquito. South Dakota State Epidemiologist Lon Kightlinger says it does well in drought weather and can breed in polluted water. It feeds on birds, humans and horses at dusk and dawn. He calls it a very aggressive mosquito.

"What's most dangerous is that it overwinters in South Dakota. It can crawl in a crack in the soil or in a barn, or in a crack in a tree, and spend the winter and come out with the virus in the spring. And that's what happened this year," says Kightlinger. "That's why we detected West Nile in birds earlier this year, and our human cases were earlier this year."

He says this species of mosquito will be most active during the next three weeks.

If you're at a game, take some (insect repellant) and spray your neighbor. - South Dakota Gov. Mike Rounds

Gov. Mike Rounds says the four deaths so far from West Nile were preventable. He says it's time to do battle with the disease and the mosquito.

"What we're trying to get across is, protect yourself, do it with deet (the active ingredient in insect repellant). Do it with long sleeves," says Rounds. "We've got a period of time here of about two to three weeks, in which we're going to have the strongest possibilities of the infection occuring. Let's get through this time period."

The state offers mosquito control training but it's up to individual communities to monitor and spray areas. This is the first year the city of Sioux Falls sprayed every neighborhood to kill off adult mosquitoes. Normally, communities spray areas where mosquitoes breed, and kill the larva.

Rounds says it's critical for people over the age of 50 to use precautions. Older people infected with West Nile can develop encephalitis, a swelling of the brain that can be deadly.

The Centers for Disease Control and Prevention says 80 percent of the people infected with West Nile virus don't show any symptoms. Up to 20 percent who are infected display mild symptoms. They include fever, headache, body aches, and sometimes swollen lymph glands or a skin rash.

About one in 150 people infected with the virus develop severe illness, including a high fever, headache, stiff neck, coma, or permanent neurological effects.

Minnesota Department of Health Epidemiologist David Neitzel says there are more than 50 mosquito species in the region. He says most of the 15 human West Nile cases in Minnesota are in counties along the South Dakota border. There are fewer mosquitoes around because of the dry weather. Neitzel says that's a problem, because people let their guard down.

"If you have a lot of pest mosquitoes out there along with these culex tarsalis -- the pest mosquitoes might remind people that, 'There's a lot of bugs out here. Maybe I should put some repellent on,'" says Neitzel. "In the absence of them, there might be just a few of these culex tarsalis flying around, and people may not put on the repellent."

The State of South Dakota is working with school districts to educate activity directors about the risks of West Nile. They're encouraging parents to send insect repellant along to football, soccer and even band practice. Gov. Rounds suggests if you're at a game, take some deet and spray your neighbor.

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