The West Nile Virus has hit Medford, although there does not yet appear to be a risk of human transmission. The infected mosquito that was found this summer is not the type that bites humans, according to Karen Rose, director of the Medford Board of Health.
The virus was detected by the East Middlesex Mosquito Control Project, which according to Donna Rheume, a spokesperson for the Massachusetts Department of Public Health, places cone-like mosquito traps at various locations, then tests the captured mosquitoes for multiple viruses. Medford pays each year to be part of the project.
No West Nile has been detected yet this year in Somerville, and it is still not clear that the case in Medford originated locally. Because mosquitoes often fly distances of over two miles, it is difficult to determine their exact place of origin, according to Rose.
Some cities and towns in Massachusetts, such as Halifax and Cohasset, have not been as lucky as Medford, as they have discovered West Nile in mosquitoes that bite humans and can transmit the disease to them.
"Some types of mosquitoes just bite birds, some mosquitoes just bite humans, some mosquitoes bite both," Rheume said.
In some of the locations where human-biting, West Nile mosquitoes have been found, officials have responded by banning planned activities during time periods when the risk of getting bitten is highest. Medford has not yet adopted such policies, but Rose said that the city was included in a conference call on that issue.
"People can still go out at night, but officials don't want large groups of people exposed, so [they] are asking [residents] to cancel scheduled activities where a lot of people may be gathering," Rose said of the restrictions in place in some areas.
According to the Centers for Disease Control and Prevention's Web site, some form of the West Nile Virus has been found in most states this year. Human cases have been found in around 30 states, including Alabama, Connecticut, Nebraska, Pennsylvania and California.
In Massachusetts, there has been only one human case this year, Rheume said. However, it involved a man from Missouri who was visiting Massachusetts and may have contracted the virus in his home state.
According to the Massachusetts Department of Health, 54 people contracted the virus in the state between 2000 and 2006, and six of those infections resulted in fatalities. The last human case discovered in Medford was in 2002.
Those who do contract the disease (only a fraction of those exposed to it) sometimes have severe symptoms.
"When the West Nile virus is bad, it causes encephalitis, which is an inflammation of the brain," Tufts Health Service's Medical Director Margaret Higham said. "People have a hard time walking or talking and can sometimes go into a coma."
One of the most dangerous aspects of West Nile is that, since it is a virus, no medication can fight it off. "Treatment is symptomatic and supportive," Higham said. This care is offered for each patient's specific symptoms with the hope that the immune system will fight off the virus and recover.
In response to the discovery of West Nile, Medford began distributing educational pamphlets and updating information on the city's Web site. The Massachusetts Department of Health also has extensive resources on its Web site and a hotline to report the discovery of dead birds, which usually serve as an indicator of the presence of the virus.
According to both Rose and Rheume, taking measures to protect from mosquito bites is the best response to a West Nile discovery.
Higham explained that protecting oneself from the virus can be as simple as staying indoors during dawn and dusk, when mosquitoes are most likely to bite, or wearing long sleeves and long pants.
Other precautions include avoiding standing water and using a mosquito repellent.
-Jamie Bologna contributed reporting to this article
