What is the mosquito-borne disease that resulted in the death of a man in New Hampshire?

In the Northeastern U.S., a rare and potentially deadly mosquito-borne disease has caused concern.

A man from Hampstead, New Hampshire, passed away last week after being diagnosed with Eastern equine encephalitis (EEE).

According to a statement from the New Hampshire Department of Health and Human Services (DHHS), the man "was hospitalized due to severe central nervous system disease and has passed away due to the illness."

A New Hampshire man, Joe Casey, is currently in the ICU on a ventilator after contracting three mosquito-borne illnesses, including EEE, according to local reports.

In an effort to control the spread of the virus, four Massachusetts towns — Douglas, Oxford, Sutton, and Webster — implemented a voluntary evening lockdown in late August.

An elderly man in Oxford, Massachusetts was confirmed as the first human case of Eastern equine encephalitis (EEE) since 2020 by the Massachusetts Department of Public Health (DPH).

The CDC has reported four cases of the virus in 2024 as of Aug. 27, but the data is subject to change.

In 2020, there were 13 cases reported; in 2021, there were 5 cases; in 2022, one case was reported; and in 2023, seven cases were reported.

The year 2019 saw a spike, with 38 cases reported.

What is Eastern equine encephalitis?

According to the CDC, EEE is a rare but serious disease caused by a virus spread through the bite of an infected mosquito.

Most cases of a certain condition in the U.S. occur in Eastern or Gulf Coast states, with only a few cases reported annually.

According to the CDC, humans and other animals that contract the virus are classified as "dead-end hosts," meaning they cannot transmit it to mosquitoes that bite them.

Dr. Eyal Leshem, director of the Center for Travel Medicine and Tropical Diseases at Sheba Medical Center in Israel, stated to Planet Chronicle Digital that although EEE is prevalent in the Western Hemisphere, it typically affects large mammals, birds, reptiles, and amphibians, and rarely causes clinical infection in humans.

What’s causing the uptick?

The potential for EEE viruses to become more common in the U.S. is increasing, according to Dr. Edward Liu, head of infectious diseases at Hackensack Meridian Jersey Shore University Medical Center.

Mosquitoes have more time to breed as warm seasons become longer, according to Liu, who spoke to Planet Chronicle Digital.

"Standing pools of water resulting from heavy rains will foster larger mosquito populations."

Dr. Marc Siegel, a senior medical analyst for Planet Chronicle and a clinical professor of medicine at NYU Langone Medical Center, stated that the virus is "rare but can be disabling neurologically and fatal."

He stated to Planet Chronicle Digital that while the occurrence is infrequent, with only a handful of cases annually, the apprehension about it is gaining traction.

Symptoms of the virus

The CDC lists fever, vomiting, diarrhea, headache, stiff neck, seizures, behavioral changes, and drowsiness as common symptoms of EEE.

These usually appear five to 10 days after being bitten.

For 30% of infected individuals, the disease can lead to fatalities.

Leshem stated that patients may display altered mental status or neurological symptoms due to inflammation in their meninges or brains.

"There is no specific drug or antiviral that has proven effective in treating EEE."

Those with compromised immune systems and older individuals are most vulnerable to mosquito-borne encephalitis.

If a disease occurs alongside other viral infections that cause encephalitis, it becomes more dangerous, according to Liu.

If mosquitoes carry more than one pathogen, it would be concerning, as ticks already do.

The only treatment for EEE is supportive care to manage symptoms.

Leshem stated that no specific drug or antiviral has been shown to be effective in treating EEE.

There is also no vaccine available for Eastern equine encephalitis.

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Liu cautioned that testing for encephalitis is not widely accessible outside of hospitals and can sometimes be inaccurate.

"It is possible that its testing may confuse two similar viruses, as the accuracy of the antibody testing we use is not always reliable."

Preventing infection

Experts concur that the most effective method of preventing infection is by safeguarding against mosquito bites.

Liu emphasized the importance of maintaining robust mosquito control programs.

"In New Jersey, mosquito control is county-based and therefore not the responsibility of individual homeowners to pay for these services."

"Testing for encephalitis is still not very available outside of hospitals, and sometimes not accurate."

The CDC advises using insect repellent, wearing long-sleeved shirts and pants, and treating clothing and gear with permethrin, an insecticide that eliminates or deters mosquitoes.

The agency advises controlling mosquitoes both indoors and outdoors to prevent infection, as stated on its website.

To prevent mosquito infestations, consider using screens on windows and doors, utilizing air conditioning when possible, and removing standing water where mosquitoes breed.