West Nile mosquito warnings renewed

Virus now in 10 counties, city is rarely fatal but incidents are spreading

April 18, 2002|By Frank D. Roylance | Frank D. Roylance,SUN STAFF

Just as Baltimoreans were beginning to enjoy the outdoors again, city Health Commissioner Peter L. Beilenson climbed to the top of Federal Hill Park yesterday to remind the city that mosquitoes infected with the West Nile virus will soon be biting again.

"We're quite likely ... to start getting cases of crows dying by late April or early May," Beilenson said.

The crows die because they've been bitten by the infected mosquitoes. Their demise signals that people also could be bitten.

Beilenson urged city residents to reduce their risk of infection by eliminating standing water on their property, where mosquitoes might breed.

Waving a plastic bucket, he said, "A kid's beach toy sitting in the back yard just two inches full could eventually harbor millions of larvae. A bottle cap could hold thousands."

Although the continuing drought may reduce the number of breeding sites, the mild winter could mean that more infected mosquitoes have survived.

The West Nile virus is believed to have been introduced into the United States in the New York City area in 1999. It has spread beyond the Mississippi River.

Maryland's first infected crow was found in Baltimore in 1999, and the virus has spread to 10 counties and the city. More than 450 dead birds tested positive for the virus last year - nearly half in Baltimore City.

First infections

The first human infections in the state appeared in August. Two of the human cases turned up in the city, three in Baltimore County and the sixth in Prince George's County.

All six victims were hospitalized with encephalitis or meningitis - life-threatening inflammations of the brain or the tissues that surround the brain and spinal cord.

Two died, but doctors said both suffered from other serious ailments that may have contributed to their vulnerability.

Beilenson said he expects more human cases this summer. But he stressed that most people have little to fear.

"The vast, vast majority of human beings bitten by West Nile-infected mosquitoes do not show any symptoms at all," he said. Except for crows, "it's pretty much an innocuous, relatively quite benign virus."

Four or 5 percent of those who are infected may experience relatively mild, flulike symptoms and recover. Fewer than 1 percent will develop life-threatening infections.

Threat to horses

The West Nile virus is also a threat to unvaccinated horses. Seven confirmed cases were found last year, all but one in Baltimore County. One resulted in the animal's death.

Beilenson said the city would be spraying pesticides again this year to kill mosquito larvae where large breeding sites are found.

But neighborhood spray campaigns to kill adult mosquitoes as they fly will be used sparingly, he said - only where large numbers of infected crows have been found or where human cases have been reported.

That policy resulted last year in an 81 percent reduction in the acreage sprayed compared with the year before.

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