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Eastern Equine Encephalitis



EASTERN EQUINE ENCEPHALITIS IS A RARE MOSQUITO-BORNE VIRAL DISEASE THAT CAN ONLY BE TRANSMITTED TO PEOPLE BY THE BITE OF AN INFECTED MOSQUITO. EASTERN EQUINE ENCEPHALITIS IS REGARDED AS ONE OF THE MOST DEADLY MOSQUITO-BORNE DISEASES IN THE UNITED STATES. SYMPTOMS INCLUDE HIGH FEVER, STIFF NECK, HEADACHE, AND LACK OF ENERGY.

The Cambridge Public Health Department leads the city's response to the risks posed by West Nile Virus, eastern equine encephalitis, and other mosquito-borne diseases.

What is the Risk in Cambridge?

EEE is not considered a threat to residents of Cambridge and surrounding cities.  While mosquitoes with EEE are trapped in the area once every few years, this is a very rare occurrence.  Most EEE-positive mosquitoes have been found south and southwest of Boston in Norfolk, Bristol, and Plymouth counties.

Eastern Equine Encephalitis in Masssachusetts

Although eastern equine encephalitis (EEE) is a very rare disease, Massachusetts has the second largest number of reported human cases in the country. Between 2004 and 2013, 82 people in the U.S. were infected with the EEE virus. Of these people, 29% (24 individuals) were infected in Massachusetts. There were no human cases of EEE virus infection identified in Massachusetts between 2014 and 2016. The virus is most often identified in mosquitoes found in and around cedar and red maple freshwater swamps.


Recent Outbreaks
Historically, outbreaks of eastern equine encephalitis occurred in Massachusetts about once every 10 to 20 years. The typical outbreak lasted two to three years. Current evidence suggests that these previously observed patterns may be changing and must be monitored carefully, according to a 2016 report from the Massachusetts Department of Public Health. The most recent outbreaks occurred in 2004–2006 and 2010–2012. 

Infected mosquitoes have been detected in Plymouth, Bristol, Franklin, Middlesex, Worcester, Norfolk, and Essex counties. The area of highest risk for transmission of EEE continues to be southestern Massachusetts, which is the historic area of risk. However, over the last 10 years, human infections of EEE have been acquired outside of these historic areas of risk.

To learn more about the risk of eastern equine encephalitis in Massachusetts, see the risk map from the Massachusetts Department of Public Health.

How to Protect Yourself

The EEE virus is carried by birds that live in natural wetlands. It is usually found only in types of birds and mosquitoes that do not bite people. However, when the virus infects large numbers of birds, the virus may infect other species of mosquitoes that do bite horses and people.

To protect yourself from eastern equine encephalitis and other mosquito-borne diseases, see the health department's prevention tips.

For more information, visit the Massachusetts Department of Public Health's mosquito-borne diseases website and the CDC’s EEE fact sheet.

Last updated on June 27, 2017


CONTACT

For general questions about West Nile virus and eastern equine encephalitis, please call 617-665-3838.