Mosquito Diseases You Need to Know About

Eastern equine encephalitis, a rare but potentially deadly mosquito-borne disease, has been in the news recently. There have been at least two deaths linked to the viral illness in the U.S. this year, one in New York and the other in New Hampshire.

There are typically only a handful of neuroinvasive cases each year. So far in 2024 there have been 13 reported cases in the Northeast and Wisconsin. There were seven reported cases in 2023 and just one in 2022. (During the past 20 years, 2019 had the most reported cases, with 38.) Most cases occur in states on the East Coast, Gulf Coast, and Great Lakes region.

Though some people have only flu-like symptoms, others develop full-blown encephalitis. About one-third of all people who develop eastern equine encephalitis die from it. Others are often left with disabilities, including intellectual impairment, paralysis, or seizure disorders.

Another uncommon but potentially severe form of encephalitis—St. Louis encephalitis—can cause manageable symptoms such as fever, headache, dizziness, and nausea. But about 90 percent of older adults who get it develop meningitis as a result, and 5 to 15 percent of those who do die. Twenty neuroinvasive cases were reported last year, 33 in 2022, 17 in 2021, and 16 in 2020, most of them in Arizona, Arkansas, California, Mississippi, and Texas.