A town in Massachusetts is shutting down its public parks and fields at night after a horse tested positive for eastern equine encephalitis, a rare but deadly disease carried by mosquitoes.

Eastern equine encephalitis, known as EEE, is a serious virus that is generally transmitted to humans through mosquito bites from infected insects. The occurrence of the disease is uncommon, with an average of 11 reported human cases each year, according to the Centers for Disease Control and Prevention (CDC).

New protocols in Plymouth, a coastal town about 40 miles southeast of Boston, were implemented after local mosquitoes tested positive for EEE and the state confirmed its first human infection since 2020.

“With the Massachusetts Department of Public Health raising Plymouth’s EEE risk level to high, it’s crucial to take additional precautions outdoors and to adhere to state and local health recommendations to reduce the risk of exposure to EEE,” stated Michelle Bratti, Plymouth’s Commissioner of Health and Human Services.

Although EEE is rare, about 30% of cases can lead to death, and many survivors suffer from long-lasting neurological problems, as per the CDC. The virus is primarily found in Eastern and Gulf Coast states. Experts have also raised concerns that climate change is fostering conditions for mosquito populations to thrive in warm, humid climates.

Massachusetts communities alert residents about the rare but deadly virus

In Plymouth, Massachusetts, where mosquitoes have tested positive for EEE, officials declared on Friday that public parks and fields would be closed from dusk until dawn, the times when mosquitoes are most active. Additionally, the town manager indicated that public parks, fields, and schools will undergo spraying in the following days.

Heightened precautions against the mosquito-borne virus in Massachusetts come five years post the state’s last outbreak, which began in 2019 with 12 cases resulting in six deaths. The state’s Department of Public Health noted that the outbreak persisted into 2020, recording five additional cases and one death. Massachusetts typically experiences EEE outbreaks every 10 to 20 years, lasting two to three years, according to the agency.

Earlier in the month, an elderly man tested positive for EEE— marking Massachusetts’ first confirmed case since 2020— prompting health officials to raise the risk levels for a number of towns nearby. They did not disclose the individual’s identity but mentioned that he was infected in Worcester County.

In Oxford, located in Worcester County, the local Board of Health unanimously recommended that outdoor events should conclude by 6 p.m. until the end of September, and by 5 p.m. from October until the first heavy frost.

Rike Sterrett, Oxford’s public health director, emphasized that this is a recommendation rather than an enforceable rule, adding that all town-sponsored events will comply with the suggested time limits. She acknowledged some resistance from families with children involved in school sports, as this could disrupt practice and game schedules.

Officials advise caution following non-human infections in other states

Officials in New York are advising caution against the mosquito-borne illness after two horses tested positive— one in Galen and another in Newburgh. Positive test results in horses typically suggest that local mosquitoes might also be carrying the virus.

Tests of mosquitoes in Rhode Island, Connecticut, and Massachusetts have also returned positive results for EEE, leading health officials to recommend that residents avoid outdoor activities during dusk and dawn. The CDC has recorded three human cases this year, with one confirmed case each in Massachusetts, Vermont, and New Jersey.

How to safeguard yourself from EEE

Eastern equine encephalitis is transmitted to humans via bites from infected mosquitoes. Symptoms can include fever, headaches, vomiting, diarrhea, seizures, behavioral changes, and drowsiness, according to the CDC.

Most individuals infected with eastern equine encephalitis are asymptomatic, according to the CDC. Anyone can be at risk, but those older than 50 and younger than 15 are the most vulnerable.

There is no available treatment or vaccine for EEE, so individuals in high-risk areas can take steps to avoid mosquito bites, which are most prevalent from dusk to dawn. Here are some recommended precautions:

• Use insect repellent
• Wear loose-fitting, long-sleeved clothing
• Utilize air conditioning and screens in windows to avoid indoor mosquito bites
• Eliminate standing water around your home to remove potential breeding sites

Contributors: Mike Murphy, Rochester Democrat and Chronicle, Henry Schwan, Telegram and Gazette