West Nile virus now found in mosquitoes in St. Louis

Monday, July 29, 2002

ST. LOUIS -- Nearly a year since dead birds around St. Louis first were found infected West Nile virus, area health officials have uncovered what perhaps was inevitable -- mosquitoes actually carrying the disease.

Mosquitoes collected in the St. Louis suburbs of University City, Hillsdale and Wellston have tested positive for the virus, marking the first time mosquitoes in St. Louis County have been found to be infected, the St. Louis County Department of Health confirmed.

Health officials swiftly cautioned that people should not be alarmed, given that the species of mosquitoes prefers to feed off of birds, not humans.

"We don't want anyone to panic," the health department's Joan Bradford said. "We're just urging people to use caution but know that not every mosquito out there is carrying any kind of virus that's going to cause harm.

"The fact that we know there are mosquitoes that have it means we want to minimize exposure, and this finding is cause for us being on alert."

To date, no cases of people contracting the virus have been confirmed in Missouri. People elsewhere have been infected by the virus usually carried by birds, though mosquitoes can transfer the virus from birds, other animals or humans.

The virus causes flu-like symptoms and, in about 1 percent of human cases, can cause a serious illness including encephalitis, an inflammation of the brain. Most people infected show no symptoms. According to the U.S. Centers for Disease Control and Prevention, 152 human cases of the virus have been reported, including 18 deaths.

"The chance of becoming ill from any one mosquito bite is extremely small on this," said Steve Fine, chief of the health department's division of public health and ancillary services.

Now in South Dakota

The virus, first discovered in the United States in 1999 in New York City, has spread to the south and west, with officials saying Friday that a dead crow found infected in South Dakota marked the farthest west the disease has been detected.

The virus has been reported in more than 30 states and the District of Columbia.

The disease first showed up in Missouri last year, when eight birds -- all crows in St. Louis city or county -- were confirmed killed by West Nile. The first confirmation of a case this year came earlier this month with the discovery of a dead blue jay in southeast Missouri's Stoddard County.

Hoping to mitigate potential human infection, Bradford said, St. Louis County has been aggressively spraying about 5,000 mosquito-breeding sites.

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