St. Louis mosquitoes test positive for West Nile virus

ST. LOUIS -- Health officials announced Wednesday they have discovered mosquitoes infected with the West Nile virus throughout St. Louis County, the first such discovery in Missouri this year.

"They're really all over," said Joan Bradford, supervisor of vector control for the St. Louis County Department of Health. The discovery was not unexpected, she said, because West Nile virus was known to be in the area.

St. Louis County tested its mosquito populations earlier than other areas of Missouri. More cases of West Nile virus could be discovered when 14 communities begin testing Tuesday, said Karen Yates, vector born disease program coordinator for the Missouri Department of Health and Senior Services.

West Nile has been on the rise over the last two years in Missouri, according to the Department of Health. Last year, the state had 77 cases, including five deaths. According to the Missouri Health Surveillance Information System, Missouri had 444 reported cases of West Nile from 2002 to 2007.

The virus can be deadly but severely sickens only one in 150 people who are infected with it, according to the U.S. Centers for Disease Control and Prevention. The small minority of people who get severely sick can suffer from high fever, disorientation, convulsions and vision loss. The symptoms can last several weeks, and neurological effects may be permanent.

About 20 percent of those infected become only mildly sick, suffering from fever, headache and vomiting. Most people show no symptoms at all, according to the CDC. People over 50 are particularly vulnerable to the disease.

While floodwaters along the Mississippi River are forming breeding grounds for mosquitoes this year, they won't breed the kind that spread West Nile, Bradford said. The kind of mosquito that carries the virus breeds in shallow puddles like those found in backyards.

The city of St. Louis will be among the communities that begin testing Tuesday.

To control mosquitoes, the county uses roving trucks to spray an insecticide called permethrin in neighborhoods and parks, Bradford said. The trucks spray in the evenings and before dawn, when the mosquitoes are most active.

While the chemical isn't extremely toxic for humans, Bradford recommends that residents avoid excessive contact with it.

The Department of Health recommends wearing insect repellent to avoid mosquito bites and reducing areas with standing water where mosquitoes breed.

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On the Net:

Missouri Department of Health and Senior Services: http://www.dhss.mo.gov

Centers for Disease Control and Prevention Web page on West Nile: http://www.cdc.gov/ncidod/dvbid/westnile/index.htm