A New Hampshire father is fighting for his life after contracting three separate viruses from a single mosquito bite.

Joe Casey, 54, has been on a ventilator in intensive care since early August when he tested positive for three mosquito-borne viruses — Eastern equine encephalitis (EEE), St. Louis encephalitis and West Nile virus, according to a fundraiser by his family.

However, his doctors are not yet sure which of the three is to blame for swelling in his brain that is so severe, the Kensington dad is barely able to communicate with his wife, Kim, and their four kids.

“He’s my brother. It’s very difficult, especially because it’s from a mosquito,” his sister-in-law Angela Barker told WBZ-TV through tears.

“He was positive for EEE, for West Nile and St. Louis encephalitis, but the CDC, the infectious disease doctors, they don’t know which one is making him this sick,” she said.

“He just got bit by a mosquito and it could happen to anybody.”

Casey has been in the ICU on a ventilator under 24-hour care, and has also undergone a tracheotomy, his family said.

“My brother-in-law is not a small man, and to see someone that you love be as sick as he is and not be able to talk, to move, to communicate for over three weeks is terrifying and gut-wrenching,” Barker added.

“Joe is going to have to go a long-term care and patient rehabilitation, that’s going to be 24-hour care, and really want to get the word out to help this incredible family,” Barker said.

EEE is a rare but serious, potentially fatal disease spread from horses to people through mosquitoes, killing about 30% of those afflicted. Those who survive commonly develop ongoing neurological issues, according to the Centers for Disease Control and Prevention. Coma and seizures are also possible.

West Nile virus is the nation’s leading cause of mosquito-borne disease, according to the CDC. There have been 377 cases of the virus in humans across 38 states in 2024, according to the agency.

The CDC warns that people infected with St. Louis encephalitis often do not have symptoms but some can develop a fever, headache, nausea, vomiting and tiredness.

There are no medications or vaccines to treat any of the three diseases, according to the CDC.

The town of Kensington, where Casey is from, discovered it had at least one mosquito pool that tested positive for EEE, the New Hampshire Department of Health and Human Services said. The town has sent out postcards warning residents and the threat level has been raised to high.

Last week, another New Hampshire man, 41-year-old Steven Perry, died after contracting EEE.

Perry, a Hampstead resident, was the first infection in the state in a decade, the state agency said.

There are typically about 11 human cases of Eastern equine encephalitis in the US per year, according to the CDC.