Understanding Eastern Equine Encephalitis

Interviewer – Can you explain what Eastern Equine Encephalitis is and why it’s important to be aware of it?

Dr. Sydney Crawley – I can. So Eastern Equine Encephalitis, or EEE, is a neurological disease caused by a virus that has the same name, and it’s a zoonotic infection. So that means it’s passed from animals to people. And it’s also considered an arbovirus because it is transmitted by an arthropod, in this case, mosquitoes. It was first recognized in horses back in 1831, and it’s very important to be aware of this virus because in very rare cases, individuals that contract the virus can actually develop Eastern Equine Encephalitis in its diseased form, which is fatal in one of three patients. And additionally, survivors that recover are actually at risk of developing very severe, permanent neurological defects, and those can range from mild to severe.

Interviewer – So, how is Eastern Equine Encephalitis transmitted, and which insects are primarily responsible?

Dr. Sydney Crawley – So Eastern Equine Encephalitis is transmitted through the bite of an infected mosquito. The virus naturally circulates through bird populations, and they serve as the reservoir. And there is a primary vector, Culiseta melanura, and that species in particular rarely attacks humans. And so it’s thought that there are approximately three, maybe four bridge vector mosquito species that spread the virus from infected animals to people.

Interviewer – Are there certain areas or seasons more prone to EEE outbreaks? And if so, why?

Dr. Sydney Crawley – There are. So most cases of this virus actually occur in the eastern coast, coastal states, or the Gulf Coast states. And outbreaks tend to occur near freshwater habitats; hardwood swamps, bogs are very common as well, and that’s just because these are the habitats where we see the virus, the vector, and the reservoirs – being birds – overlapping. And the primary vector, Culiseta melanura, prefers low-wind swamp areas.