This summer, eastern equine encephalitis (EEE) has been found in mosquitoes across the state. This month, four people have been diagnosed with the virus. One of those four, a woman from Bristol County, died this weekend. This is the first time human cases of EEE have been diagnosed in the state since 2013. Dr. David Hooper is the chief of the infection control unit at Massachusetts General Hospital. Dr. Hooper spoke with WGBH Radio’s Jeb Sharp about EEE. This transcript has been edited for clarity.
Jeb Sharp: I don't think we can do enough of the basics on this. So what is EEE?
Dr. David Hooper: EEE is a virus that is transmitted by mosquitoes and it has the particular ability to infect both birds and humans — sometimes horses, hence the name.
Sharp: And just to make sure I'm understanding it, how exactly is it transmitted?
Hooper: It's transmitted by bites of mosquitoes. In fact, the virus is in birds, and there are certain mosquitoes that bite birds and transmit to other birds. And then there are other mosquitoes that bite birds and then bite humans.
Sharp: What are the symptoms?
Hooper: Well, it's important to put in perspective that not everyone who gets bitten by an infected mosquito comes down with the disease. It's been estimated that maybe one in 30 people who were exposed to the virus by an infected mosquito bite will actually become sick.
And then usually when a person becomes sick, it starts out with a non-specific sort of flu-like illness — fever, muscle aches — and then in some people, but not all, it then progresses from that point. It varies from person to person in the particulars, but confusion, loss of consciousness, seizures are the ones that are most commonly found.
Sharp: Maybe this is morbid curiosity, but is the virus actually attacking brain cells, destroying them?
Hooper: It can, yes. It can replicate within brain cells and in so doing, damages them — which is one of the reasons why even if someone is able to survive, there's often residual neurologic findings and abnormalities due to that damage of the brain cells themselves.
Sharp: And what is the treatment?
Hooper: Unfortunately, there are no specific treatments. Supportive therapy is the particular treatment that we have available. There are no antiviral agents or antibodies that are yet available.
Sharp: And do you understand why some people die and some don't? And does that have to do with how quickly they get some kind of care?
Hooper: Certainly the symptoms that bring people to medical attention usually are not the very first symptoms because they're pretty non-specific. It's when people then get a particularly severe headache or their family members or they note that they're confused that brings them to medical attention.
Why some people go on to that and others don't, isn’t fully understood. It is understood that there's an age difference. The likelihood of developing EEE is higher in the extremes of age, in children and older adults.
Sharp: And how long would it be between someone getting it and showing up with that terrible headache or other symptoms?
Hooper: Between four and 10 days after being bitten by an infected mosquito, then some symptoms appearing at that point. Unfortunately, it can be a very severe infection and 30 to 50 percent of patients with EEE in fact die. And a 30 to 80 percent of the people who survive may have residual neurologic abnormalities.
Sharp: And can you tell us how localized the danger is? How much does the geography matter?
Hooper: The geography of this particular virus is largely in the eastern United States, and even within Massachusetts at the current time, the more exposure risk is in the southeastern part of the state.
Sharp: And I ask, of course, because, as a resident of Massachusetts, should we all be taking the same precautions? Or does it matter whether you're in one of these locations?
Hooper: Well if you take overall risk, yes, it's probably higher risk in those locations, but it seems prudent at this time of year where EEE or other mosquito-borne viruses like West Nile virus can emerge to just to do common sense things in terms of avoidance of mosquitoes, and that involves a number of factors. Obviously, keep screens on the windows so that you keep the mosquitoes out, use long sleeve clothing — shirts and long pants — when going outside, use mosquito repellents DEET and other related ones are highly recommended, and also avoid going out at the times that these particular mosquitoes are most active and most likely to bite humans or other mammals. And that would be at dawn and dusk.
