West Nile Virus Risk Level Raised To 'High' In 27 Massachusetts Communities

BOSTON (CBS) -- The Massachusetts Department of Public Health on Friday raised the West Nile Virus risk level from moderate to high in 27 cities and towns in the Boston area. The decision was made due to four recent human cases and the first animal case discovered in a Middlesex County alpaca.

Health officials are seeing an increase in the Culex mosquito population, which carries the virus, and they say recent rainy weather conditions are favorable for mosquito activity.

The communities seeing their risk level raised are Lynnfield and Saugus, in Essex County; Arlington, Bedford, Belmont, Burlington, Cambridge, Everett, Lexington, Lincoln, Malden, Medford, Melrose, Newton, Reading, Somerville, Stoneham, Wakefield, Waltham, Watertown, Winchester, and Woburn in Middlesex County; Brookline in Norfolk County; and Boston, Chelsea, Revere, and Winthrop in Suffolk County.

Click here to see the West Nile Virus risk map for the entire state.

"September is the month when we are most likely to see people get infected with West Nile virus," said Acting Public Health Commissioner Margret Cooke in a statement. "While we advise everyone to take steps to avoid mosquito bites, this is especially important if you are over the age of 50 or have an immune compromising condition. It is also important to know that as overnight temperatures get cooler, mosquito activity right around dusk and dawn may be more intense."

Most people infected with West Nile Virus do not experience symptoms, but people 50 and older are at a higher risk for severe disease. Symptoms can include fever and flu-like illness.

People can avoid mosquito bites by using repellent, wearing long-sleeved clothes and pants and staying inside during the peak mosquito hours of dusk and dawn.