The Hampstead residents infection was the first in the state in a decade, the New Hampshire Department of Health and Human Services said Tuesday. The resident, whom the department only identified as an adult, had been hospitalized due to severe central nervous system symptoms, the department said.

About a third of people who develop encephalitis from the virus die from the infection, and survivors can suffer lifelong mental and physical disabilities. There is no vaccine or antiviral treatment available for infections, which can cause flu-like symptoms and lead to severe neurological disease along with inflammation of the brain and membranes around the spinal cord.

When it does cause an infection, it is very, very severe. Although its a very rare infection, we have no treatment for it, said Dr. Richard Ellison, immunologist and infectious disease specialist at University of Massachusetts Memorial Medical Center. Once someone gets it, its just - all we can do is provide supportive care, and it can kill people.

Nationally, the burden of eastern equine encephalitis can vary from year to year. There are typically about 11 human cases in the U.S. per year, according to the U.S. Centers for Disease Control and Prevention. There were seven cases nationally last year, but more than 30 in 2019, which was a historically bad year in which at least a dozen patients died, according to federal data. (AP)

FILE PHOTO: A biologist examines a mosquito in Salt Lake City, Utah, Aug. 26, 2019. Eastern equine encephalitis, a deadly mosquito-borne illness, claimed a rare human victim in the northeastern U.S. state of New Hampshire this week