Is West Nile Virus Coming to the South End?

After a particularly tough year for the West Nile virus in 2012, Massachusetts health officials are bracing for what could be another busy summer for the mosquito-borne illness. Although, with so many factors playing into the problem, the track of West Nile is not an easy one to predict, said Kevin Cranston, director of the Bureau of Infectious Disease for the Massachusetts Department of Public Health. “We can’t pin down all of the elements that go into why one season is bad and another season is not,” Cranston said. But if this summer is similar to last summer—marked by extended periods of very hot weather—some parts of the state could see a high number of cases as occurred in 2012. To give residents a sense of West Nile’s prevalence in the South End, Patch has pulled together county-level 2012 data from the Centers for Disease Control and Prevention.  Different factors play into outbreaks  Long periods of warm weather can help accelerate the maturation of the type of mosquitoes known for spreading West Nile virus, Cranston said. Rainfall also might play a part in the problem, as these mosquitoes thrive in pools of stagnant water. But there are other factors, too, related to mosquito abundance and activity and the amplification cycle of the virus. The West Nile virus “season” lasts from around mid June until the first “killing frost”—when temperatures drop below 32 degrees for several hours in the local environment, effectively killing that area’s mosquito population, Cranston said. Testing to begin soon The Bureau of Infectious Disease begins collecting and reporting on mosquito samples the week of June 17 and continues testing throughout the season, Cranston said. West Nile virus is reported through two main processes. First, the bureau works with the local mosquito control projects to trap and sort mosquitoes by species—different species are known for spreading different viruses. A pool of about 10 to 15 mosquitoes is then tested for the presence of viruses such as West Nile and Eastern Equine Encephalitis, or EEE. “If even one mosquito in that pool has the virus it is considered to be a positive pool. We assemble that data over time to show how a given region of the state is more or less likely to have infected mosquitoes in the environment,” Cranston said. Information also comes in from physicians when patients report symptoms that may be caused by West Nile virus. Samples are taken from the individual and tested at the state lab in Boston’s Jamaica Plain. This not only helps the physician make a diagnosis and treat the patient but also assists the state in establishing risk […]

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