WASHINGTON – Transmission of West Nile virus has likely frozen to a halt this year in Maryland, but health officials said the state can expect to see the virus again next year.
Recent freezing temperatures have killed many of the mosquitoes that spread the disease and “driven the rest into hibernation.” said Don Vandrey, spokesman for the Maryland Department of Agriculture.
To see a reoccurrence of West Nile virus this season, temperatures would have to stay around 60 degrees overnight for “at least a couple of nights in a row,” Vandrey said.
But Maryland hasn’t seen the last of the virus.
The virus was first discovered in the state in 1999 in only one bird, according to the state health department’s web site. The number of infected birds jumped to 50 of the 950 birds tested in 2000, and jumped again this summer to 417 birds out of about 1,400 tested.
Five infected humans were found this year, along with four infected horses. Neither humans nor horses were found infected before this year.
Of the five humans affected, three were from Baltimore County and two were from Baltimore City. One victim died, but not from the virus, said Baltimore City Health Commissioner Peter Beilenson.
“West Nile virus is not a major public health threat,” said Beilenson. “Compared to the flu, which actually affects more people, West Nile virus is not something people should be concerned about. We had more cases and a lot more deaths with the flu this year than West Nile.”
With the exception of 16 blue jays and a cooper’s hawk, all of the infected birds were crows. This season, 203 birds were found in Baltimore City, 83 in Baltimore County, 69 in Prince George’s County, 38 in Montgomery County, 11 in Howard County, four in Harford County, three in Anne Arundel County, two in Carroll County, two in Frederick County, one in Charles County, and most recently, one in Cecil County.
The state found 17 West Nile-positive mosquito pools out of over 12,500 tested. Of those, 13 were in Baltimore City, two in Prince George’s County, and one each in Baltimore and Howard counties. No infected pools were found in 2000.
West Nile virus is spread to humans by bites from infected mosquitoes, but most people are not affected by the virus. People over the age of 50, or those with immune system deficiencies have the highest risk of developing the disease.
The Maryland Department of Health and Mental Hygiene says that “less than 1 percent of persons exposed to the virus will develop more severe infections,” and rare cases could lead to meningoencephalitis and possibly death.
West Nile virus is commonly found in Africa, Asia and the Middle East. It first appeared in the Western Hemisphere in 1999 when several crows were found infected in New York. Several people fell ill and 10 have died, nine in New York and New Jersey and one this year in Atlanta.
While health officials expect West Nile to be back next year, Beilenson said it is moving south and west, so Maryland “may have more cases, may have less cases.”