'Remain vigilant': Mosquito season renews concerns about rare but deadly EEE virus


With the pandemic dominating health headlines, it’s easy to forget about mosquito-borne diseases — even as mosquito season enters its peak during the hot summer months.

The threat is real, especially after a particularly deadly season for Eastern equine encephalitis least year. Health officials have called EEE "one of the most dangerous mosquito-borne diseases" in the U.S. and there are concerns it’s finding new opportunities to spread.

The virus — which is more virulent than West Nile — can cause inflammation of the brain that leads to death in about one-third of cases. People who do survive are often left with brain damage.

Only a few human EEE cases are reported in the U.S. each year — there were just six cases in all of 2018, for example. But 2019 brought an unexpected and alarming spike: 38 people were infected and 15 of them died, according to the Centers for Disease Control and Prevention.

Most infections happened in Massachusetts and Michigan, but cases were also reported in Alabama, Connecticut, Georgia, Indiana, New Jersey, North Carolina Rhode Island and Tennessee.

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How the 2020 season will turn out depends on whether rainfall amounts and temperatures will be higher than typical, said Joe Conlon, a retired U.S. Navy entomologist and spokesman for the American Mosquito Control Association.

“It would be prudent to remain vigilant and make preparations for at least the same levels as last year,” Conlon told TODAY.

“Mosquito season is just beginning to enter its peak time frame and mosquito control districts have been assiduously preparing for this the entire spring. It’s what they do. That being said, people probably are suffering a bit of ‘health emergency fatigue’ at this point and are bit less likely to fret over mosquito-borne diseases at the moment.”

People should know the new coronavirus isn’t transmitted through mosquitoes or ticks, according to the CDC and the World Health Organization. Coronaviruses have never been shown to be transmitted in that manner, Conlon added.

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Most cases of EEE are usually reported in Atlantic and Gulf Coast states, the CDC said. But in 2019, the virus “had spread in an unprecedented pattern, showing up in regions where it had previously not been seen before,” according to a report published Wednesday in OneZero, a Medium publication.

EEE is seen from late spring through early fall, but the report noted that as the Northeast warms due to climate change, it’s expected to have a longer period without freezing temperatures between spring and fall by 2035, increasing the period during which insects can spread diseases, including EEE.

How EEE spreads:

The virus grows in birds that live in swamps. When a mosquito that feeds on both birds and mammals bites an infected bird, it can then transmit the virus to horses and other animals and, in rare cases, people.

Anyone in an area where the virus is circulating can get infected, though people who work or exercise outdoors, or live in wooded areas face the highest risk.

Most people have mild symptoms or none at all, but in severe cases, a person may experience headache, high fever, chills and vomiting four to 10 days after being bitten. As the disease progresses, the patient can suffer from disorientation, seizures and coma. There is no specific treatment.

“They give you palliative care and you either get better or you die,” Conlon told TODAY last year.

As humans move closer to and deeper into hardwood forests, they’re increasing their risk, he noted. Climate change plus human travel and migration may also play a role in mosquito-borne diseases, potentially exposing half of world’s population to disease-spreading mosquitoes by 2050, an analysis published in Nature Microbiology in 2019 found.

But other studies have found the ban on the insecticide DDT, rather than a warming climate, may be responsible for mosquitoes thriving in the U.S. It appears many factors are at play.

“If the climate change that’s occurring is producing higher temperatures and more rainfall, that’s going to abet this type of disease transmission,” Conlon noted. Before the coronavirus pandemic, the world was constantly getting smaller as travel continued to get cheaper and more accessible.

“We’re putting travelers in contact with these exotic diseases that are a seven-hour plane flight away,” he added. “They’re bringing these diseases, in some cases, back to the U.S.”

His main concern was keeping mosquito-borne disease like Rift Valley fever, found in Africa, and yellow fever, found in South America and Africa, out of the U.S.

How to reduce the chance of getting a mosquito-borne disease:

  • There is no vaccine for EEE, so preventing mosquito bites is key.

  • Stay indoors at dawn and dusk, when the mosquitoes that transmit the virus are active, Conlon said.

  • Use a mosquito repellent with an EPA-registered ingredient.

  • Mosquitoes need water to breed, so get rid of anything in your yard that holds water.

Originally published