Triple E vs West Nile Virus: What’s the Difference?

MMosquito-borne diseases are on the rise, and we haven’t even started talking about mosquito season yet.

Last summer, news of dengue fever at the Paris Olympics caused concern, but there are two other diseases on the rise in the U.S. right now: West Nile virus and Eastern Equine Encephalitis (also known as EEE or Triple E). Both can only be contracted through the bite of an infected mosquito.

While they’re still relatively rare, they’re not impossible to get, and the illnesses can lead to serious complications for some. Recently, former National Institutes of Allergies and Infectious Diseases director Anthony Fauci, MD, was hospitalized for six days after contracting West Nile virus. According to STAT News , he said of his symptoms, “I honestly felt like I got hit by a truck.” And last week, a New Hampshire man died from Triple E, according to CBS . According to Today , additional cases have been reported across New England.

Why are mosquito-borne diseases on the rise? It likely comes down to the ecology of the mosquito, William Schaffner, MD, a professor of preventive medicine and health policy in the division of infectious diseases at Vanderbilt University, tells Well+Good.

“We had a mild winter, so a lot of them didn’t get killed. Then we had a warming season, which expanded the geographic range and lifespan of the mosquito population. We also had a very wet season, which gave mosquitoes plenty of breeding grounds,” Dr. Schaffner added. It’s all a perfect recipe for increased mosquito populations and infection, leading public health officials in some states to advise residents to stay indoors during dawn and dusk (when mosquitoes are most active).

We know they’re both on the rise, but how are Triple E and West Nile virus different? And how likely are you to contract either one? We spoke to a pathologist who specializes in vector-borne infections (also known as mosquito-borne diseases) and Dr. Schaffner about the differences between the diseases and how you can best protect yourself.

What is West Nile Virus?

Although it is not widespread, West Nile virus is the leading cause of mosquito-borne illness in the U.S., according to the Centers for Disease Control and Prevention (CDC). It is usually spread from bird to bird through mosquito bites, but people can also get it after being bitten by infected mosquitoes, Dr. Schaffner says. “West Nile virus has been endemic in the U.S. since about 1999, when the first cases of the disease were found in several states during the summer. This started primarily on the East Coast and over a period of four or five seasons it moved west,” he says.

According to Bobbie Pritt, MD, a pathologist and clinical microbiologist with a special interest in vector-borne infections at Mayo Clinic Laboratories, cases typically increase around August and September, which is peak mosquito bite season. Bites occur most frequently around dawn and dusk, when mosquito populations are highest.

When people contract West Nile virus, they are considered “dead terminal hosts.” That means the disease cannot be passed from person to person, Dr. Pritt says. (The only exceptions to this are an organ transplant from an infected person, Dr. Pritt says, or if you are a health care provider exposed to an infected person’s open wound or injury, the CDC says.)

What is the Triple E virus?

Triple E stands for Eastern Equine Encephalitis. This rare but deadly mosquito-borne disease was first discovered in the 1830s in horses in Massachusetts (hence the name), and the first human case was identified in 1938, according to the Center for Food Security and Public Health (CFSPH). Today, it’s most commonly found in North America and the Caribbean and can infect horses, humans, and birds such as ducks and emus. It circulates most frequently between mosquitoes and birds in wetland environments, according to the CDC.

Since 1964, only a few hundred cases of Triple E have been identified in the U.S., with outbreaks most often occurring in late summer, according to the CFSPH. Like West Nile, humans (and in this case horses) are considered “dead-end hosts.” Both humans and horses can develop serious illness and complications from this disease.

Where are they found and how common are they?

In general, West Nile virus can be found throughout the U.S., while Triple E is more localized to the northeastern and Gulf Coast states, Dr. Schaffner says. According to the CDC, as of August 27, there have only been 289 human cases of West Nile virus in 33 states. States with the highest number of cases are Texas, California, Pennsylvania and New York.

“Meanwhile, only a few cases of Triple E are reported each year,” Dr. Pritt says. (According to the CDC, there are an average of 11 cases per year.) This year, Triple E has been reported in only five states, including Massachusetts, New Hampshire, New Jersey, Vermont and Wisconsin.

People at higher risk are those you might suspect: older adults, people with underlying health conditions or people with weakened immune systems, Dr. Schaffner says. You’re also at higher risk if you work outdoors, travel to the tropics or are a health care worker, the CDC says.

Symptoms of Triple E vs West Nile Virus

The symptoms of West Nile disease and Triple E are very similar.The time between the first bite and when you actually feel symptoms coming on can be anywhere from a few days to a few weeks. It may just be a headache and a mild fever that goes away after a few days,” says Dr. Pritt.

About 70 to 80 percent of West Nile virus cases are mild, she adds. “You might just think, ‘I must have had some kind of virus,’ and then you feel normal again,” she says.Mild symptoms of both include chills, body aches, joint pain, and other flu-like symptoms. Dr. Pritt says you may also get a rash of flat or raised lesions called a maculopapular rash. Often, these symptoms go away within a week or two.

That said, severe cases of Triple E and West Nile virus are a little different. Unlike the flu, which is an upper respiratory infection, mosquito-borne illnesses are systemic, meaning they can affect your entire body, particularly your nervous system and neurological function. Both can cause something called neuroinvasive disease, Dr. Pritt says. With West Nile virus, “about 1 percent develop neuroinvasive disease, where the virus invades the brain or central nervous system,” she adds.

Both Triple E and West Nile virus can cause serious complications, such as meningitis (i.e., inflammation around the membranes of the brain and spinal cord), encephalitis (i.e., inflammation of the brain) or other long-term complications, such as difficulty walking, tying shoes or doing other daily tasks, mental and cognitive problems or even bedriddenness, Dr. Pritt adds. While the symptoms are similar, Triple E is more likely to cause serious illness.

Is one deadlier than the other?

While West Nile virus is more common and widespread in the U.S., Triple E is more dangerous. “I view (Triple E) as the worse of the two,” Dr. Pritt says. About 30 percent of people who get severe Triple E will die, according to Dr. Pritt and the CDC. This is different from the 1 percent of people who get severe illness from West Nile virus, of whom “10 percent will die, and probably most of them will have long-term deficits,” Dr. Pritt says. These complications can range from cognition and mental problems to neurological and mobility problems.

Bottom line: Triple E is often more deadly than West Nile and appears to pose a greater threat to long-term health. And it doesn’t necessarily discriminate: While there are certain people who are at higher risk, Dr. Pritt says people in their 50s and younger are also at risk for serious illness.

Triple E vs West Nile Virus Treatment

Unfortunately, there’s no cure or specific treatment for any of these mosquito-borne illnesses, Dr. Pritt says. If you do develop a severe case that requires hospitalization, healthcare providers will offer supportive therapies to help your body heal. According to Dr. Pritt, this could include a ventilator to help you breathe better or medications to help treat inflammation in the brain or meningitis. Because there are no vaccines or cures, it’s essential that you protect yourself from mosquito bites in the first place. “Prevention is key here,” Dr. Pritt says. (More on that below.)

How to Protect Yourself from Triple E and West Nile Virus

Mosquito bites may not seem like a big deal, but both Dr. Schaffner and Dr. Pritt noted that the insects are among the deadliest creatures on the planet. When we’re seeing an increase in mosquito-borne diseases, preventing bites in the first place is key. According to both Dr. Schaffner and Dr. Pritt, staying indoors during dawn and dusk can help reduce exposure (though you can still get bitten by an infected mosquito in the afternoon, they point out).

Other measures include wearing insect repellent when you go outside, especially if you’re near water or in heavily wooded areas, wearing long, loose clothing to protect your skin, and removing sources of standing water from around your home (e.g., birdbaths, old tires, buckets, or children’s plastic toys that collect water after rainstorms, Dr. Schaffner says). If you plan to be outdoors for an extended period of time, such as hiking or camping, you may want to douse your clothing, boots, and gear in a substance called permethrin. It’s an insect repellent that can help prevent tick and mosquito bites, Dr. Pritt says.

When it comes to insect repellents specifically, Dr. Pritt recommends looking for ones with 30 percent DEET, or using natural lemon eucalyptus oil repellents, which can work just as well as DEET. If you’re having trouble finding the right type of repellent for you, the Environmental Protection Agency has an interactive page where you can explore the different types, ingredients, and how long each repellent lasts.

When should you see a doctor?

“This summer, we’re asking people to think of[mosquitoes]not as a nuisance, but as a potential health risk,” Dr. Schaffner says. “We’re asking people to take them more seriously.” While the chances of a serious infection are low, it’s still possible to contract these diseases, especially if you live in an area where infected mosquitoes have been identified. (You don’t have to be in the woods; the mosquitoes could be in your backyard, he adds.)

If you know you’ve been bitten recently and develop a fever, chills, fatigue, or a headache that goes down your neck, see your doctor as soon as possible to rule out mosquito-borne illness. Your doctor can perform tests to help distinguish between Triple E and West Nile virus (or other viruses) and get you the proper care you need.