Mosquito-Borne Illnesses Have U.S. on High Alert - How Real Is the Risk?

Key Takeaways

• West Nile virus has been reported in 33 states this year, and has so far led to 18 deaths.
• Eastern equine encephalitis (EEE) virus, also transmitted by mosquitoes, has been reported in four states and has caused one death.
• Both viruses cause flu-like symptoms, and usually resolve on their own, but certain groups are vulnerable to severe illness.

As Americans get outdoors to enjoy the last weeks of summer, public health officials are urging everyone to take precautions against insect bites as the threat of mosquito-borne illnesses rises.

Nearly 300 cases of West Nile virus have been reported in 33 states so far this year, killing at least 18 people, according to the Centers for Disease Control and Prevention.

Among those infected was Anthony Fauci, MD, the former director of the National Institute of Allergy and Infectious Diseases, who was hospitalized with severe symptoms last month.

A less widespread disease, eastern equine encephalitis virus (EEE), has infected four people in four states this year, and a 41-year-old New Hampshire man who was otherwise healthy died of EEE infection in August.

"It's déjà vu all over again," says Richard Pollack, PhD, a senior environmental public health officer at Harvard University in Boston, about the seasonal return of these viruses. "West Nile virus spread from coast to coast some years ago, and it is here to stay, and you can expect it to be encountered in most any community every year."

He adds that EEE is generally restricted to some traditional hot spots, such as southeastern Massachusetts. The virus is likely to return each late summer and early fall - although it does not necessarily come back every year.

West Nile and EEE Attack the Central Nervous System

Primarily spread through mosquito bites, both the West Nile and EEE viruses infect the central nervous system and can cause a range of symptoms, including:

• Fever
• Headache
• Body aches
• Vomiting
• Diarrhea
• Rash

"When I had West Nile virus, I was the sickest I've ever been," said Lyle Petersen, MD, the director of the CDC's division of vector-borne disease, in an August 31 post on X . "I was a marathon runner at the time, yet couldn't make it up the stairs. It took six months to fully recover."

Overall, however, severe illness from these viruses is rare, says Stephen Rich, PhD , a professor in the department of microbiology at the University of Massachusetts in Amherst. Dr. Rich studies zoonotic diseases that originate in animals but may spill over into human populations.

"For most people, these diseases are self-resolving," says Rich, meaning they get better on their own. "Eventually your immune system wipes them out without treatment, and often without any signs of illness."

He does note that EEE virus is deadlier than West Nile, albeit less widespread. Nearly a third of those who develop EEE die, while the fatality rate with West Nile is 3 to 15 percent.

"EEE is also less discerning in terms of the age profile of the people that it makes very sick," says Rich. "West Nile virus, on the other hand, tends to be a disease that causes the most problems in very old people or very, very young people who may not have well-developed immune systems."

There is no specific medicine or vaccine for either virus. Those infected may relieve symptoms with supportive treatment, including good hydration, pain relievers, and plenty of rest.

Take Precautions to Avoid Mosquito-Borne Infection

People living in areas of the country where the viruses are most prevalent are advised to take extra precautions against mosquito bites.

Although West Nile is in more than half of states, the disease is most prevalent in Texas, Nebraska, Nevada, California, Arizona, New York, Pennsylvania, and Illinois. At this time, EEE is in just four states: Massachusetts, New Jersey, Vermont, and Wisconsin.

To avoid mosquito bites, public health officials recommend:

• Wear protective clothing such as long pants, long-sleeved shirts, and socks.
• Limit outside activity between evening and dawn when mosquitoes are most active.
• Use insect repellent on exposed skin.
• Empty water from buckets, cans, pool covers, flower pots, and other items to eliminate standing water around buildings and driveways when possible.
• Clean out clogged rain gutters.
• Fix or install window and door screens.
  
  

To help stop the spread of mosquito-borne illnesses, New York City and parts of Massachusetts have been spraying communities with pesticides.

People with known sensitivities to chemicals or with respiratory conditions like asthma are encouraged to stay indoors during spraying to reduce the chances of aggravating those conditions.

Rich notes that some communities in his state of Massachusetts have set up voluntary curfews on outdoor activities to protect residents.

"It gets controversial when decision makers say we're going to close down parks or cancel evening events, concerts, and football games," he says. "If you do curtail your outdoor activities a little before dusk [and at dawn], however, you will be making a meaningful reduction in your exposure to mosquitoes."

The good news is that colder fall weather should soon be here, and when the first hard frost comes (two consecutive hours of temperatures below 28 degrees F), virtually all mosquitoes die.

"Hopefully, we'll get a nice hard frost in early October, and the mosquito season will be done for the year," says Rich.

Editorial Sources and Fact-Checking

Everyday Health follows strict sourcing guidelines to ensure the accuracy of its content, outlined in our editorial policy . We use only trustworthy sources, including peer-reviewed studies, board-certified medical experts, patients with lived experience, and information from top institutions.

Sources

1. West Nile Virus. Centers for Disease Control and Prevention . August 27, 2024.
2. Illinois, Wisconsin report their first West Nile virus deaths of 2024. CNN . August 30, 2024.
3. Bean K, LaPook J. Dr. Anthony Fauci Recovering at Home After Hospitalization for West Nile Virus. CBS News . August 24, 2024.
4. NH DHHS Identifies Person Infected With Eastern Equine Encephalitis Virus in New Hampshire. New Hampshire Department of Health and Human Services . August 27, 2024.
5. About West Nile. Centers for Disease Control and Prevention .
6. About Eastern Equine Encephalitis. Centers for Disease Control and Prevention .
7. MacDonald R, Krim V. West Nile Virus. Canadian Family Physician . June 2005.
8. Protect Yourself Against Eastern Equine Encephalitis and West Nile Virus. New Hampshire Department of Health and Human Services .
9. Mosquito Control. NYC Health . September 2024.
10. Mosquito Control and Spraying. Mass.gov . September 2024.
11. Information for Determining the End of the Mosquito Season and Other Public Health Recommendations. Mass.gov .

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Don Rauf

Author

Don Rauf has been a freelance health writer for over 12 years and his writing has been featured in HealthDay, CBS News, WebMD, U.S. News & World Report, Mental Floss, United Press International (UPI), Health , and MedicineNet. He was previously a reporter for DailyRx.com where he covered stories related to cardiology, diabetes, lung cancer, prostate cancer, erectile dysfunction, menopause, and allergies. He has interviewed doctors and pharmaceutical representatives in the U.S. and abroad.

He is a prolific writer and has written more than 50 books, including Lost America: Vanished Civilizations , Abandoned Towns , and Roadside Attractions . Rauf lives in Seattle, Washington.

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