Why West Nile Virus Risk Level In Boston Has Been Upgraded

BOSTON, MA — The risk level for West Nile Virus in Boston has been elevated from low to moderate, according to the latest Boston Public Health Commission data released Thursday.

Officials said that a moderate risk level means that infection with West Nile Virus—which is carried by mosquitos and can be spread to humans through a bite—is likely or has already occurred. A low risk level means infection with West Nile Virus is unlikely.

Department of Public Health officials told Patch that one of the criteria that establishes an area as being at moderate risk is sustained or increasing West Nile Virus activity in mosquitoes in the focal area.

Sustained activity is defined as when positive West Nile Virus mosquito samples are detected for at least two consecutive weeks within one focal area, according to officials.

West Nile Virus in mosquitos was identified on July 6 in Brookline, followed by a positive sample in Boston on July 18, then 6 positive samples from two different locations in Watertown, officials said.

"Taken together, these data indicate increasing risk in the focal area," officials added.

While no human cases of the virus have yet been confirmed in Boston, health officials say it’s likely that city residents will become infected at some point.

Some people might become infected without knowing it, according to officials.

Last week, the Boston Public Health Commission confirmed that a mosquito pool in South Boston tested positive for West Nile Virus.

It was the first time this summer the virus had been confirmed in Boston, officials said.

“The Boston Public Health Commission works closely with our partners at the State Department of Public Health to monitor mosquito pools and alert residents of the risk of West Nile Virus,” Dr. Bisola Ojikutu, Commissioner of Public Health and Executive Director of the Boston Public Health Commission, said last week's news release.

The Boston Public Health Commission encourages residents to take steps to protect themselves against mosquito bites.

“During this time of the year and into the fall, we encourage residents to protect themselves by using insect repellant and wearing long sleeve clothing when outside at dusk and dawn for prolonged periods of time," Ojikutu said.

According to officials, most people who are infected with West Nile Virus do not experience any signs or symptoms. In some cases, people will experience a headache, fever, nausea, vomiting, and body aches which can last for a few days or several weeks but usually go away on their own, officials said.

However, in rare cases, the virus can cause serious symptoms including high fever, severe headache, confusion, lack of coordination, and muscle paralysis or weakness, officials said.

People who are 50 years old or older are more likely to become sicker from the virus than younger people, according to officials. Anyone with serious symptoms should get medical help immediately, officials said.