West Nile virus has been detected in mosquitoes collected last week in Waltham, the state Department of Public Health said yesterday.
The virus is typically spread to humans through the bite of an infected mosquito. While people of all ages can be infected, those over 50 stand a higher risk for severe illness.
Donna Rheaume, DPH spokeswoman, said the public should take a number of steps to protect themselves from mosquito bites, including using mosquito repellents and avoiding outdoor activities between dusk and dawn - the peak biting times for the insects.
Those who must go outside when mosquitoes are most active are urged to wear long sleeves, pants and socks to reduce the amount of skin that is exposed.
"Certainly the risk is with us until the first frost," Rheaume said."We want people to reduce the risk as much as possible."
Rheaume said no human cases of West Nile virus have been reported so far this year in Massachusetts. Last year, there were six human cases of the virus reported statewide.
Waltham Public Health Director Walter Sweder said to his knowledge, no human cases of West Nile have been reported in Waltham.
However, Sweder said this isn't the first time that mosquitoes collected in Waltham have tested positive for the virus.
According to the state DPH Web site, 62 groups of mosquitoes collected from around the state this year have tested positive for West Nile virus while 43 birds have tested positive. Sweder said other measures that can be taken to prevent exposure to mosquitoes are to fix any holes in screen doors and eliminate standing pools of water around the house, where mosquitoes are likely to breed.
Sweder said the city does have a mosquito control program in place.
"We have a very aggressive mosquito control program here in Waltham," Sweder said.
West Nile originates in birds and is spread from bird to bird by infected mosquitoes. In humans, the virus can cause illnesses including a mild fever to more serious diseases such as encephalitis or meningitis.
In the United States, West Nile was first identified in New York during the summer of 1999. Since then, it has spread throughout most of the country.
Richard Conn can be contacted 781-398-8004 or rconn@cnc.com.
