New Hampshire resident dies after EEEV infection, as rare, lethal mosquito-borne virus spreads in New England

New Hampshire health officials said Tuesday that a person who tested positive for the mosquito-borne infection eastern equine encephalitis virus (EEEV) has died. 

An adult from Hampstead, New Hampshire, who tested positive for EEEV infection, “was hospitalized due to severe central nervous system disease, and has passed away due to their illness,” the New Hampshire Department of Health and Human Services (DHHS), Division of Public Health Services (DPHS) said in a statement. “DHHS offers our sympathies to the individual’s family and friends.”

EEEV is a rare but serious disease transmitted to people by infected mosquitos. The last reported human EEEV infection in New Hampshire was in 2014, when DHHS identified three human infections, including two fatalities, according to the department. In addition to the person with EEEV infection announced Tuesday, EEEV has been detected in one horse and seven mosquito batches in New Hampshire so far this summer. 

“In New Hampshire, mosquitoes transmit infections including Eastern Equine Encephalitis Virus, West Nile Virus, and Jamestown Canyon Virus,” New Hampshire State Epidemiologist Dr. Benjamin Chan said in a statement. “We believe there is an elevated risk for EEEV infections this year in New England given the positive mosquito samples identified. The risk will continue into the fall until there is a hard frost that kills the mosquito [sic]. Everybody should take steps to prevent mosquito bites when they are outdoors.”

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New Hampshire health officials said EEEV can cause flu-like symptoms such as fever, chills, muscle aches, and joint pain. 

EEEV can also cause severe neurological disease, such as inflammation of the brain and membranes around the spinal cord, known as encephalitis and meningitis, respectively. Approximately one-third of all people who develop encephalitis from EEEV die from their infection, and many others experience life-long physical or mental impacts, according to the department. There is no vaccine or antiviral treatment for EEEV. 

EEEV has also been detected in neighboring states. In Massachusetts, one person, one horse and 69 mosquito samples have tested positive, and in Vermont, one person and 47 mosquito samples have tested positive. Vermont state health officials on Aug. 9 announced the first human case in the state since 2012. That case involved a male in his 40s from Chittenden County who was hospitalized on July 16 and left the hospital a week later.

The U.S. Centers for Disease Control and Prevention estimates there are about 11 human cases of eastern equine encephalitis in the U.S. per year. 

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New Hampshire health officials warned residents to prevent EEEV infection by taking steps to prevent mosquito bites, including using effective mosquito repellents, wearing long sleeves and pants when outside, and avoiding outdoor activities in the early morning and evening hours when mosquitoes are most active. 

The department said it is also important for residents to remove standing water from around their homes to reduce mosquito populations, and ensure doors and windows have tight-fitting screens without holes.

Over the weekend, the Massachusetts Department of Public Health (DPH) and the Massachusetts Department of Agricultural Resources (MDAR) announced plans to conduct aerial spraying for mosquitoes in areas of Plymouth County, and truck-mounted spraying in parts of Worcester County. As of Saturday, 10 communities in Massachusetts were raised to high or critical risk for EEEV.

“We have not seen an outbreak of EEE for four years in Massachusetts,” Massachusetts DPH Commissioner Robbie Goldstein. MD, PhD said in a statement Saturday. “This year’s outbreak and activity raise the risk for communities in parts of the state. We need to use all our available tools to reduce risk and protect our communities. We are asking everyone to do their part.” 

The town of Plymouth, about 40 miles southeast of Boston, said Friday it was taking “proactive measures” amid the high risk status for EEEV by closing all parks and fields from dusk until dawn.