Buzz Off

Buzzing at your head, biting at your ankles, leaving behind itchy, red welts — mosquitoes are just plain pesky. But that’s not the only reason to slather on the bug repellent. The insects can also carry viruses such as West Nile and eastern equine encephalitis (EEE), which can cause serious illnesses. Both viruses have been detected in mosquitoes in Massachusetts this summer.

About 20 percent of those infected with West Nile virus will develop symptoms, such as fever, headache, body aches, nausea, vomiting, and sometimes swollen lymph glands. A skin rash may also appear on the chest, stomach, and back. Fewer than one percent of those infected will develop severe illness, including encephalitis or meningitis. 

“Severe West Nile virus is more common in persons over 50 years of age,” says Cheryl Barbanel, director of BU’s Occupational Health Programs and the Occupational Health Center and a School of Medicine associate professor of medicine. “Most persons infected with West Nile recover, although a small number may have persistent neurological deficits.”

The virus has been detected in Boston every summer since 2000, according to the Boston Public Health Commission. Between 2000 and 2006, the Massachusetts Department of Public Health documented 54 cases of West Nile virus infection, with 6 deaths. This summer mosquitoes carrying the virus have been collected in several communities, including West Roxbury, Jamaica Plain, Medford, Marlborough, Brookline, Weymouth, and Berkley. As of September 4, two cases in humans were reported in Massachusetts, both of which are believed to have been contracted outside the state.

Often mosquitoes pick up the virus by feeding on infected birds. “Luckily, no birds have tested positive,” says Barbanel.

Eastern equine encephalitis can be more serious. The first symptoms of EEE, which appear 3 to 10 days after a person is bitten by an infected mosquito, are fever, stiff neck, headache, and lack of energy. The disease worsens rapidly, and patients may go into a coma within a week of being infected. Inflammation and swelling of the brain, called encephalitis, is the most dangerous and frequent complication.

“If people have any of the symptoms, especially neurological symptoms,” says Barbanel, “they should contact their physician or seek care in an emergency department,”

The most recent outbreak of EEE in Massachusetts began in 2004, and there have been 13 cases and 6 fatalities through 2006. The virus has been detected this summer in Raynham, Seekonk, Easton, and Rehoboth. The first human case of EEE in the region this year was reported recently in Newton, N.H., just over the Massachusetts border.

“EEE is rarely found in mosquitoes in Boston, and as of August 13 no EEE has been detected in the city this season,” says Barbanel. “Persons over age 50 and younger than age 15 seem to be at greatest risk for developing severe EEE when infected with the virus.”

Mosquitoes are most active between late July and late September, but if the weather remains warm the risk period can continue as long as November.

The state Executive Office of Health and Human Services offers tips to protect yourself against these mosquito-borne illnesses:

•    Avoid being outside during peak mosquito hours, from dusk to dawn.
•    Wear long sleeves, long pants, and socks when outdoors, if possible.
•    Apply insect repellent containing DEET, permethrin, picardin, or oil of lemon eucalyptus when going outdoors.
•    Mosquito-proof your home by draining standing water and installing or repairing window screens.

For more information, contact the Boston Public Health Commission’s Communicable Disease Control Division at 617-534-5611.