PITTSFIELD -- Tests have confirmed the presence of West Nile Virus in mosquitos here and in the Ashley Falls section of Sheffield, according to the state Department of Public Health.
These are the second and third positive test for West Nile in Berkshire County this year, following a similar result in Pittsfield on June 26. Samples were collected at surveillance sites on July 13 and 17. West Nile was first detected in the area last September.
The Berkshire County Mosquito Control Project will be placing additional surveillance traps in the area where the virus was found and catch basins have been treated with a biological larvicide to reduce the population of the mosquito species.
Christopher Horton, superintendent of the Berkshire County Mosquito Control Project, said positive tests in this region typically come at the end of August or early September, so it's surprising to have a third positive test before the end of July.
West Nile grows in birds and is spread by mosquitos.
Horton said there is an amplification effect on the disease caused by more frequent contact between birds and the mosquitos. Horton said he believes the early occurrences this year could be tied to the dry weather conditions, which have resulted in birds and mosquitos searching out some of the same scant water supplies.
There have been 15 instances of West Nile detection in mosquito populations in Massachusetts in 2012. There have been no confirmed cases of human infections in Berkshire County.
Most West Nile infections don't cause symptoms, but it can cause fever, rash, headache and body aches. The disease can be fatal for a small percentage of infected people.
Health officials are asking residents to be vigilant and to take precautions to avoid mosquito bites.
About West Nile virus
West Nile virus is a mosquito-borne illness. Here are tips to avoid getting bitten by a mosquito:
- Avoid outdoor activity between dusk and dawn, when mosquitos are most active
- When outdoors, use repellent, wear long pants, socks and long-sleeved shirts
- Drain standing water, which mosquitos could use to lay eggs. Check rain gutters and drains; empty any unused flowerpots and wading pools, and frequently change water in birdbaths.
- Install or repair screens.
Symptoms of West Nile virus in humans:
- Eighty percent of those infected will exhibit no symptoms.
- Fewer than 20 percent will exhibit symptoms such as fever, headache, body aches, nausea, vomiting and sometimes swollen lymph glands. They may also develop a skin rash on the chest, stomach and back.
- Less than 1 percent of those infected will develop severe illness, including encephalitis or meningitis. The associated symptoms include high fever, headache, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, vision loss, numbness and paralysis. People over 50 are at a higher risk to develop severe illness.
- Between 2000 and 2010, 67 people have reported West Nile infection in Massachusetts. Six of those people have died.
Source: Massachusetts Department of Public Health
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