Massachusetts is home to more than 50 mosquito species, several of which are capable of spreading disease to humans. The West Nile virus and eastern equine encephalitis are the two most significant mosquito-borne diseases known to occur in Massachusetts. Culex pipiens, or the “common house mosquito,” is considered to be the primary vector of West Nile virus in the state, and it relies largely on standing water in urban areas in order to reproduce. This species is also believed to be a vector of eastern equine encephalitis (EEE), but another species known to be abundant in woodlands and urban areas of Massachusetts, Culiseta melanura, is likely the primary vector of EEE.

Generally, mosquitoes rarely transmit the West Nile virus and EEE in Massachusetts. However, 2019 year saw 12 reported EEE cases in the state, and three of these cases proved fatal. Naturally, many Massachusetts residents want to know if EEE will become a threat this year as well. According to one public health expert in Massachusetts, the water present on the ground this spring will largely determine whether or not EEE-carrying mosquitoes become abundant in the state during 2020.

Mosquitoes become infected with EEE when they collect a blood meal from birds carrying the virus. The mosquito species known to contract EEE from birds overwinter in marshland, and water has remained abundant in marshes, which will allow emerging mosquitoes to breed in great numbers. If rainfall becomes heavy this April, EEE-carrying mosquitoes will be able to breed in urban and suburban areas. Therefore, it is too early to tell whether or not EEE-carrying mosquitoes will become prevalent near human-populated areas in Massachusetts this year. Outbreaks of EEE occur in 10 to 20 year cycles, and 2019 was the first year of a new cycle in Massachusetts, while the previous cycle occurred in 2010. Between 2010 and 2012, nine EEE cases, four of which proved fatal, occured in Massachusetts, making the current cycle unusually hazardous to Massachusetts residents.

Do you take measures to prevent mosquito bites before leaving your home during the spring and summer?