What Mosquitoes Carry Eastern Equine Encephalitis?

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Eastern Equine Encephalitis (also known as EEE, Triple E and sleeping sickness) is a rare but very serious illness. It is transmitted to humans and horses by the bites of infected mosquitoes and, though uncommon, kills a handful of people in the United States every year.

The best way to protect yourself from Triple E (and other mosquito-borne illnesses for that matter) is to educate yourself on the risks.

So, what types of mosquitoes carry EEE? what percentage of these are infected? And, most importantly, how can you stop them from biting you?

What is Eastern Equine Encephalitis?

Eastern Equine Encephalitis (EEE) is a rare but potentially fatal illness that causes infections of the brain. The EEE virus was first identified in horses (hence the name), but can also be spread to humans through the bite of an infected mosquito.

Most people who are infected with EEE will not develop any symptoms. Others will develop a milder form of the disease, known as a systemic infection. This usually results in flu-like symptoms, such as:

  • Fever
  • Chills
  • Joint pain
  • Muscle pain
  • General discomfort and feeling unwell

Around 5% of people who are infected with EEE will develop a far more serious condition known as encephalitis.

This is a highly dangerous infection that causes swelling and inflammation in the brain, causing symptoms such as:

  • Vomiting
  • Diarrhea
  • Drowsiness
  • High fever
  • Headache
  • Irritability
  • Changes in behavior
  • Loss of appetite
  • Confusion
  • Seizures
  • Coma

Encephalitic EEE is a serious infection that is thought to kill about 30% of sufferers. Those who survive the infection are often left with lasting neurological problems, which can impair their cognitive function and motor skills. Others suffer from seizures and some even develop personality disorders after a bout of EEE.

There’s no doubt about it, EEE is a terrifying illness. But, how scared do you need to be? How common are EEE infections, and what can you do to protect yourself?

How common is EEE in the United States?

EEE is a very serious and potentially fatal illness but, fortunately, it’s also incredibly rare. Only a handful of cases are reported in North America each year, and 2019 saw only 9 EEE deaths in the US.

For a lot of people, however, that’s 9 too many – so how can you protect yourself from contracting the deadly EEE virus?

Do all mosquitoes carry EEE?

No! Most mosquitoes don’t carry any diseases, and those that do are highly unlikely to be harbouring the EEE virus.

What mosquitoes carry EEE?

Mosquitoes that are known to carry and transmit EEE to humans include:

  • Coquillettidia pertubans
  • Aedes sollicitans
  • Ochlerotatus canadensis

Most cases of EEE in the United States are reported in the Eastern and Gulf coast states, and the risk of infection is highest in the summertime. Mosquitoes that carry EEE are most often found in wetland or swamp habitats, so people working in these areas are most at risk of infection.

What percentage of mosquitoes carry EEE?

The good news is that only a very tiny percentage of mosquitoes in the United States carry EEE. There were around 47,500 cases of mosquito-borne diseases reported in the USA in 2016, but only 118 (that’s a little over 0.2%) of those were EEE. It’s also important to remember that not every mosquito bite results in disease – far from it! The vast number of people who are bitten by mosquitoes walk away with nothing more than an itchy bump.

It’s impossible to know exactly how many mosquitoes carry Triple E. However, your chances of catching any kind of illness from a mosquito in the United States is slim, and EEE cases represent only a very tiny number of those.

What other mosquito-borne diseases are there in the United States?

EEE may be uncommon, but it’s far from being the only mosquito-borne disease in the United States. Other illnesses that can be caught from mosquito bites include:

  • West Nile Virus
  • Zika Virus
  • Malaria
  • Dengue virus
  • Chikungunya
  • La Crosse encephalitis
  • Jamestown Canyon encephalitis

How can you protect yourself from EEE infection?

The only way to protect yourself from Triple E (and other types of mosquito-borne illnesses) is to prevent mosquito bites.

Use insect repellent

A good insect repellent is one of the best ways to keep mosquitoes (and other types of biting bugs) away from your skin. Sprays containing DEET or picaridin are highly effective, though natural repellents can also work well.

Wear long, loose-fitting clothing

Creating a physical barrier between bugs and your skin is another foolproof way to prevent bites. Long, loose-fitting clothing is a great way to keep mosquitoes and other insects off your skin.

Install screens at home

Keep in mind!

Screens are a highly effective way to keep mosquitoes (and other pests) out of your home. This is especially important if you live in an area where mosquitoes are common.

Sleep under a net

If you live in an area with lots of mosquitoes, or where diseases like EEE are known to exist, a mosquito net is a must-have. Sleeping under a net is the only way to guarantee you won’t be bitten at night, which is critical for preventing mosquito-borne illnesses.


Eastern Equine Encephalitis is one of the deadliest mosquito-borne illnesses in the United States. Fortunately, it’s also very rare, and only a tiny percentage of mosquitoes are thought to carry the virus. It is most prevalent in Eastern and Gulf Coast states, particularly in wetland and swamp areas.

People working in these areas during summer have the highest risk of contracting the virus, but wearing repellent spray and protective clothing is advisable for everyone. EEE may be uncommon but it’s far from being the only bug-borne disease in the USA, and preventing bites is the only way to avoid infection.

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