A rare and dangerous mosquito-borne disease is spreading across New England, with one person already confirmed to have died from the infection and states on high alert.
Cases of Eastern Equine Encephalitis (EEE) have been confirmed in at least five states this year: Massachusetts, Vermont, Wisconsin, New Jersey and New Hampshire.
The Massachusetts Department of Public Health warned over the weekend that 10 areas of the state are at high or very high risk for EEE virus transmission, and a New Hampshire resident was confirmed to have tested positive for EEE and died this week.
EEE, also known as “triple E,” is transmitted by the bite of an infected mosquito. There is no vaccine or treatment for the virus. The mosquito-borne disease is rare in the United States but can be deadly.
Here's what we know:
This is a rare disease that occurs in coastal areas.
As a disease spread by mosquitoes, EEE occurs primarily in coastal areas of the United States, such as New England and New Orleans.
“Certainly, the two major areas in the United States where this disease has occurred in the past have been New England and the Gulf Coast,” said Dr. David Hamer, a professor of global health medicine at the Boston University School of Public Health.
“We've had hundreds of cases in Massachusetts over the last 70 years,” Hamer added, “and we might have a few years without a case, and then we'll have one or two. But we think it's happening a little more frequently.”
Factors such as increased travel and global warming may be contributing to the rising incidence of mosquito-borne diseases such as EEE, Zika, dengue fever and malaria.
According to the Centers for Disease Control and Prevention (CDC), the United States typically sees between three and 15 cases of EEE per year, with a national average of seven cases per year. Seven cases were reported in 2023.
Cases tend to peak between July and September.
“CDC is in contact with affected states to offer assistance, and we encourage Americans to follow the guidance of their state and local health authorities,” the agency said in a statement. “While EEE infections are rare, this is not a new virus, and CDC has been monitoring sporadic infections in the U.S. for years.”
Most people are unaware that they are infected
Most people with EEE don't know it and don't have any symptoms, said Luanne Barnabas, chief of infectious diseases at Massachusetts General Hospital.
“95% of people who are infected have no symptoms at all, are healthy and unaware they have the virus,” Barnabas said.
“But in 5 percent of cases, you'll see symptoms like fever and chills. And it can actually affect the central nervous system, causing confusion, abnormal movements and even encephalitis. And when that happens, about a third of cases are fatal.”
When asked for more information by The Hill, the CDC said it is not currently aware of any deaths from EEE other than one confirmed in New Hampshire this week.
Infections can be severe and life-changing
The small number of people who develop severe cases of EEE may experience flu-like symptoms such as fever, aches, joint pains, chills, etc. More severe symptoms include neurological conditions such as meningitis and encephalitis (inflammation of the brain).
Most people experience asymptomatic infection, but about 30 percent of those who develop severe symptoms will die. According to the CDC, about half of people who survive a severe EEE infection will experience long-term complications.
Infection usually lasts for one to two weeks, but side effects can be long-term. The CDC lists intellectual disability, personality disorder, seizures, paralysis, and impaired cranial nerve function as potential long-term effects of EEE infection.
There is no vaccine or cure for EEE, and treatment of infection is primarily supportive care to reduce the severity of symptoms.
“There are a lot of supportive therapies that can help reduce the inflammation that's associated with encephalitis,” Hamer said, “so there may be steps we can take in the hospital and intensive care unit to reduce not only the risk of death but also the risk of developing complications.”
Risk factors unknown
Unlike other diseases spread by mosquitoes, it is not known whether certain groups are at higher risk of severe illness from EEE.
West Nile virus is thought to affect older people and those with weakened immune systems more severely. Children under the age of five, pregnant women, and people with HIV or AIDS are thought to be more seriously affected by malaria.
However, EEE appears to affect different groups in the same way.
“When you look at the cases, it appears to be teenagers, people in their 30s and 40s – healthy people with no obvious risk factors – getting infected. So I think with Eastern horses, everybody needs to be careful,” Hamer said.
A New Hampshire man died from EEE. Healthy at 41 According to his family, he had no underlying health conditions.
Avoid infection
Although rare, avoiding EEE infection is the same as avoiding other mosquito-borne diseases.
“Wear long sleeves. If you have standing water or pots or anything like that, turn the pots upside down and get rid of the standing water,” Barnabas said, adding that the first frost of the year later this year should kill any remaining mosquitoes.
CDC Recommended insect repellent Ingredients that deter mosquito bites include DEET, picaridin, IR3535, lemon eucalyptus oil, paramenthanediol, and 2-undecanone.
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