If you live in northern Vermont or other places in the northeast, you’ve surely heard the buzz about EEE (Eastern Equine Encephalitis, pun intended). We are currently under high alert in several areas as mosquitos infected with the virus that causes EEE have been found.
But what does “high risk for EEE” mean, and how worried should I be? Understanding EEE is key to making informed choices and minimizing anxiety.
People hear “high risk” and “30% mortality” and understandably get super worried. Phones in doctors’ offices are ringing off the hook, and people are scheduling appointments because they have been bitten by a (or several) mosquito. As a doctor, I want to take a moment to discuss the actual risk of contracting EEE to help people be less worried (while still promoting all the easy and prudent measures you can take to avoid getting bitten by a mosquito carrying EEE).
Encephalitis, which means brain swelling, can be caused by many different things. Encephalitis caused by EEE is serious. The mortality rate for EEE encephalitis is 30%. Survivors of EEE encephalitis are often left with permanent neurologic complications.
In other words, EEE can be super serious and you don’t want to get it. That’s the bad news.
The good news is about the low incidence of mosquitoes infected with EEE and the extremely low frequency of EEE encephalitis in humans. To say it more clearly, very few mosquitoes have EEE, and even if you have the misfortune to be bitten by a mosquito with EEE, it’s very unlikely that you will go on to develop EEE encephalitis. Understanding EEE allows everyone to assess their own risk and take appropriate precautions.
In Vermont, 75 out of a total of 2,703 pools of mosquitos tested positive for EEE. That means that in MOSQUITOS, less than 3 out of 100 mosquitoes (3%) test positive for EEE.
Now, this mosquito infection rate varies by region with the high-risk areas having more EEE-infected mosquitoes than the low-risk areas, but overall, infectivity in mosquitos, while higher than in most years, is still pretty low. As far as the likelihood of being bitten by an infected mosquito, if you have a few bites, take a deep breath- the odds are that you won’t be infected.
The next piece of good news is that the vast majority of people bitten by an EEE-infected mosquito get no symptoms at all. Of those who do get symptoms, the vast majority of them (95-98%) get flu-like symptoms of fever and body aches which resolve after 1-2 weeks with symptomatic care at home. People over age 50 or younger than age 15 are at greatest risk for developing severe disease.
Remember, flu-like symptoms can be caused by the flu, COVID, a viral infection, or a tick-born illness (all of which you are statistically MUCH more likely to have than EEE). Once flu season starts, in late fall or early winter, flu-like symptoms are likely flu or Covid.
Now, going back to our discussion of understanding EEE and how likely it is that you might get EEE encephalitis, of the people who have been bitten by an EEE-infected mosquito, and who do get symptoms, only about 2-5% may develop encephalitis, which, as previously discussed, is devastating.
Encephalitis causes sudden high fever (103° to 106°F), stiff neck, severe headache, and altered mental status. The disease can sometimes worsen quickly. About one-third of people who develop EEE encephalitis will die. There is no treatment and care is primarily supportive. This remote possibility is serious and this is why EEE is in the news. But understanding EEE helps assuage our tendency to panic.
We don’t really know the exact number of people bitten by an EEE-infected mosquito because most don’t develop symptoms, but the reality is that we see encephalitis from EEE very rarely. Historically, in the whole US, there are usually only about 11 cases per year of human encephalitis caused by EEE virus.
In other words, the severe disease, while extremely dangerous, is also very rare.
In VT, there has been 1 reported case of a human testing positive for EEE this year, and this is the only human case reported in VT since 2012. From reading the news reports, it is unclear to me if this infected person had encephalitis or if they had flu-like symptoms and tested positive for EEE. So far, in 2024, there have been no EEE cases in animals reported. Since 2012, when EEE was first reported in VT, there have been 6 animal cases, with one fatality in a horse in 2023.
So, now that you understand EEE and know that you have a very low risk of catching it, what should you do?
First and foremost, AVOID GETTING BITTEN by mosquitoes. This is a surefire way to avoid getting infected. Other tips include:
- Dont go outside from dusk to dawn, if you can help it
- Use an EPA-registered mosquito repellent
- Wear heavy, long sleeve clothes with a mosquito netting hat if you need to be out in the evening
- Check your property for standing water pools and drain them if you are able (ie bird baths, kiddie pools, etc)
- Consider using mosquito dunks (biologic mosquito larvae disrupter) in standing water near your home
Don’t freak out if you do get bitten- the odds are in your favor. Understanding EEE helps!
Second, should you develop symptoms consistent with EEE, TEST FOR COVID (at the onset of symptoms and every couple of days for about a week)!!! The likelihood that you have Covid or some other viral illness FAR outweighs the likelihood that you have symptomatic EEE.
I’m seeing a lot of Covid presenting with headache, body ache, fever, and chills with minimal upper respiratory symptoms lately. Accordingly, if you have Covid-like symptoms, you should:
- Test for Covid
- Mask
- Stay away from people
- Drink plenty of fluids
- Take acetaminophen or ibuprofen for symptoms
As the cooler weather of fall approaches, and the EEE risk declines, consider getting vaccinated for both flu and Covid (there is a new formulation of Covid vaccine out currently). Early October is often a great time to be vaccinated to be protected through cold and flu season and the predictable winter holiday Covid wave.
Symptoms of encephalitis (persistent high fever, altered mental status, severe headache with stiff neck, and pain with looking at light) should prompt evaluation by a medical professional. Emergency medical care is indicated in these cases.
I hope that understanding EEE lets you feel more reassured about your very low risk of contracting EEE. I am promoting prudence (around mosquito bite prevention) without worry.
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