PITTSFIELD -- More West Nile Virus and Eastern Equine Encephalitis sites have been confirmed by Berkshire Coun ty Mosquito Control Project surveillance.
Positive samples for West Nile were taken from Cheshire Road, upper North Street, Fort Hill and West streets as well as West Housatonic Street.
Two sites in Pittsfield -- Elm Street and West Hous atonic Street -- tested positive for Eastern Equine Encephalitis (EEE). Surveillance sites vary each week and are used to detect any lo cal outbreaks of viruses trans mitted by mosquitoes.
"Eastern Equine is a lot more deadly than West Nile," said Chris Horton, the superintendent for Berk shire County Mos quito Con trol Project. "There’s a 30 or 40 percent higher mortality rate."
Two cases of the West Nile Virus were also found on South State Street and Route 8A in North Adams.
Cases were also found near the Stockbridge Bowl in Stockbridge, and two cases were reported near Route 7 and Ashley Falls in Sheffield.
Both viruses are carried by birds. If a mosquito feasts on one that is infected, a virus can easily be transmitted to a human.
The sites are examined for diseases by the county’s Mosquito Control Board by testing a dead egg-carrying female mosquito’s reaction to an antibody, according to Horton.
Though the viruses were found at specific sites, potentially infected birds and mosquitoes roam freely, so the viruses cannot be confined to those areas.
"We’ve set 100 traps and that’s taking only a tiny sample of the local mosquito population," said Horton. "We have to assume it’s throughout the county."
It’s a valid cause for concern, according to Kevin Cranston, the executive director of the Massachusetts Department of Public Health’s Bureau of Infectious Diseases, and people should take the appropriate actions.
"People should avoid being outside during the time when most mosquitoes are out, which is from dusk until about dawn," Cranston said. "They should apply bug spray that contains DEET, or wear long sleeves and long pants if the weather permits."
In response to the discovery, the Berkshire County Mos quito Control Project will organize ground-based adulticide applications to reduce the adult mosquito population. Areas with a larger mosquito population will be targeted along with the zones that tested positive, according to an announcement from the Mosquito Control Project.
Mosquito population control begins as soon as the season transitions from winter to spring, with Control Project officials spraying a larvicide. It’s basically impossible to eradicate the entire local mosquito population with just the larvicide, Horton said, so an adult mosquito spray is used for the remainder of the season until the first hard frost.
"We’ve had several hits already," Horton said. "This is usually the beginning of the time that we’d start looking for [the viruses]."
In Berkshire County, West Nile Virus was first discovered in Sheffield last year. This is the first year EEE has been found in western Massa chusetts.
"It probably has something to do with the recent heat and the mild winter we had," Horton said.
The first case of West Nile Virus was found in New York City in 2000. EEE has been traced in the U.S. since the late 1930s, according to Cranston.