You may have heard the news about a rare mosquito-borne illness that is on the rise in the United States. It’s called eastern equine encephalitis (EEE), and while the risk of exposure has typically been low, a recent surge in infections has raised a lot of concern about this potentially deadly virus. 

We’ve been tracking the progress of EEE since August, keeping a close eye on its spread and the impact the virus has on the communities it encounters. We know the details can seem overwhelming, and in the wake of a worldwide pandemic, the news of another outbreak can be deeply unsettling. That’s why today, we’re here to break down everything you need to know about EEE and, most importantly, how to keep yourself and your family protected from this virus and others like it. 

Overview of Mosquito-Borne Illnesses

Mosquito-borne diseases are caused by microscopic bacteria, viruses, or other parasites that travel from the bloodstream of one animal into another through mosquito bites. Some of the most common examples include malaria, West Nile virus, Zika, yellow fever, and dengue, though dozens of others can be found in mosquito-prone areas around the world. Altogether, these diseases cause over 700 million infections each year and over a million deaths globally, with malaria alone accounting for 748,000 in 2021. 

We’re not trying to scare you. Rather, we want to help put things in perspective. Your risk of serious infection by mosquito-borne diseases is significantly reduced with vaccination, and even if you are infected, most have a high infection rate but a relatively low mortality rate.
But that’s where EEE differs. 

Why Is Everyone Talking About Eastern Equine Encephalitis?

On August 23, 2024, in Plymouth, MA, city officials closed parks from dusk until dawn after a horse in the area was diagnosed with EEE. Why was this necessary? 

Mosquitoes Are Carriers of EEE

Let’s talk about disease vectors. A vector is any living being that transmits a pathogen to another, whether it’s an animal, plant, or some other form of life. For example, deer ticks are a well-known Lyme disease vector, and, being the only proven vector for this disease, the only way to catch it is through a tick bite. This also means there is no person-to-person transmission, making humans a dead-end host. 

EEE typically cycles between birds and mosquitoes, specifically a species of mosquito called Culiseta melanura. Here’s how it usually works:

1. A carrier mosquito bites a bird.
2. EEE begins to multiply in its new host.
3. Another mosquito bites the bird, becoming a carrier of the virus.

We say “typically” because this cycle can be broken when another species of mosquito enters the picture. We call these “bridge vectors.” Bridge vectors allow this otherwise isolated disease to cross over to new hosts, including humans and horses. In fact, EEE was first discovered in horses during a 1933 outbreak, which is where the “equine” in the name comes from. This is what happened in Plymouth, and it’s a big deal. 

What’s Different About EEE in 2024?

The presence of an infected horse in Plymouth indicated that EEE was bridging from birds to mammals, and sure enough, cases of human infection followed shortly. 

At the time of writing, there have been no fewer than 10 cases of EEE in the United States, including four in Massachusetts and at least one as far west as Wisconsin. Of those cases, at least two have resulted in death, with one in New Hampshire and another in New York. 

This is consistent with EEE’s unusually high mortality rate of 30%, and even among survivors, severe neurological problems are common. We won’t go into all the symptoms, but you can find the CDC’s complete list here. Mild cases tend to include fever, chills, and muscle aches, while severe infections can lead to convulsions and potentially life-threatening brain damage. Unfortunately, there is no vaccine for eastern equine encephalitis, but there is one reassuring detail—the virus cannot pass between humans. 

Just like Lyme disease, humans are dead-end hosts for EEE. What’s out of the ordinary is the number of cases we’re seeing, as the yearly average for EEE in the U.S. hovers around 11, a case count that has likely already been surpassed. This means a large number of mosquitoes are acting as bridge vectors for the virus. As mosquito populations in the U.S. expand, along with an ever-growing mosquito season, so will the risk of infection. 

Frequently Asked Questions about Eastern Equine Encephalitis

Should I Be Worried About Catching EEE in California?

Despite the alarming spread and high mortality rate, your risk of catching EEE is low. At this time, no cases have been reported in the western U.S., and while the development of this outbreak is being monitored closely by the CDC, your best bet right now is to exercise caution rather than concern. 

Eastern equine encephalitis is not the only mosquito-borne disease on the rise in the U.S. West Nile virus, which is far more prevalent than EEE, led to the first mosquito-related death in the Bay Area in over two decades this past July. That’s why now, more than ever, it is important to limit your exposure to mosquitoes through awareness and effective pest control. 

5 Ways To Avoid Mosquito-Borne Illnesses

• Avoid peak mosquito times. Mosquitoes are most active at dawn and dusk, so try to limit outdoor activities during these times.
• Wear protective clothing. Cover up with long sleeves, pants, and socks to reduce exposed skin when outdoors.
• Use insect repellent. Apply an EPA-approved repellent containing DEET, picaridin, or oil of lemon eucalyptus to protect against mosquito bites.
• Keep doors and windows closed or screened. Use screens on windows and doors to prevent mosquitoes from entering your home.
• Remove standing water. Reduce the standing water around your home, such as in birdbaths, flower pots, and gutters, to prevent mosquito breeding.

The best approach will always be the professional one. So when you want to be sure you have the highest level of protection against mosquitoes this fall, reach out to Dewey Pest and Termite Control for your free quote and consultation.