Sept. 25, 2019 — This is a particularly bad season for the potentially fatal Eastern equine encephalitis — the rare mosquito-borne EEE that has infected almost 30 people from seven states this year. In the United States, an average of seven EEE cases are reported each year, according to the CDC.
A second Connecticut resident died this week from the disease, bringing the national death toll to nine. Even though the number of confirmed cases is still very low compared to, for instance, West Nile virus, many governments are urging people to stay indoors or are increasing their mosquito spraying programs. One reason for the concern is that an estimated 30% of people who get EEE die from it.
WebMD talked to William Schaffner, MD, an infectious diseases specialist at Vanderbilt University Medical Center, about the infection, its effect on the body, and how to avoid it:
WebMD: What makes EEE so dangerous?
Schaffner: This is a virus that does not normally infect humans. When it gets into people, it is a very nasty infection. It has an attraction to the central nervous system, especially the brain. When it gets to the brain, it destroys brain cells. It creates an inflammatory response, which causes fluid to get around the brain. The brain is encased by the skull, so it can’t expand, causing increased pressure, which compromises brain function.
WebMD: Why are there more cases this year?
Schaffner: We’re not entirely sure. Let’s put it into context: This is a pretty unusual infection in humans. The virus circulates among wild birds and is transmitted by mosquitoes. It lives in that ecologic niche, particularly swampy water. That’s its habitat. It’s been an infection largely on the Gulf Coast and East Coast. Occasionally, a different mosquito species gets in the middle of this — one species that will bite both horses and humans, so infections can occur in those species.
It has raised speculation about climate change. One of the things that will happen, if you get a wetter and warmer climate and more prolonged seasonal warmth, you get more mosquitoes. That’s an increased opportunity to exploit this ecologic niche. The military calls it collateral damage — you get infection in horses, and in people — species that are not usually part of the virus ecology.