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Home / Health / What to know about EEE, a mosquito-borne virus on the rise

What to know about EEE, a mosquito-borne virus on the rise



I f you live in Massachusetts or Michigan, you're probably hearing a lot of questions about something called EEE.

But 2019 is turning out to be a big year for Eastern equine encephalitis, generally called EEE – "triple E" – for short. And if it has not hit your radar yet, it likely will.

We think you'll have questions.

What is EEE?

Eastern equine encephalitis is one of several New World encephalitis viruses. It is also known as arbovirus – that is spread by a mosquito or other arthropod. West Nile is another kind of arbovirus.

The virus is found in the northeast of the country as well as along the Great Lakes and the Gulf Coast. It is also occasionally found in Canada;

In a word: severe.

Actually, some people have mild, fluent Marc Fischer, a medical epidemiologist with the Center for Disease Control and Prevention's Arboviral Disease Branch, located at Fort Collins, Colo.

But about 20% of the people infected with clinical illness and about half helped of them develop neuroinvasive disease ̵

1; in which the virus moves into and inflames the brain, triggering encephalitis.

It can start with the sudden onset of a headache, high fever, chills, and vomiting, and lead to disorientation and seizures. 19659003] The death rate is high: About a third of EEE patients who develop encephalitis die. And survivors of severe EEE often have lasting side effects, including mild to severe brain damage.

"It is the highest case of fatality of all arboviruses that occur in the United States," Fischer said.

How common is EEE?

That's the good news. It is not common at all. "

From 2009 to 2018, 21 states recorded 72 human EEE cases, the CDC reports. Most had only single cases during that decade; Florida (13), Massachusetts (10), New York (8), Michigan and North Carolina (7), and Georgia (6) are more than just a handful of human cases over that period.

The CDC says the United States has an average of seven cases a year.

That is far less common than West Nile virus cases, of which there are generally hundreds each year , West Nile virus, including 21 deaths – and this is not a bad year for West Nile.

But it seems to be shaping up to be a bad year for EEE, is not it? Why?

Six states have reported 20 cases of EEE so far this year, with Massachusetts – a historic hot spot for the virus – recording nine cases and Michigan reporting seven. 2019 are New Jersey, North Carolina, Rhode Island, and Connecticut.

 EEE Graph

There were EEE year, said Scott Weaver, to arbovirus expert at the University of Texas Medical Branch at Galveston.

"I It's still only mid-September, "said Weaver, who heads the Microbiology and Immunology department at UTMB. "In Massachusetts and other areas of the northeast and mid-Atlantic, we may have another month or even more to do with transmission and more cases to come."

Some years are more active than others when it comes to these kinds of viruses , explained Fischer.

"Every few years you get a higher number of cases. And they can be in different places. Massachusetts has historically had a higher number of cases. But there are other states. Florida typically has the most cases overall, "Fischer said. "So it moves around, it occurs in different places in different years. And they have high and low years. "

What is the virus' life cycle?

19659003] If you know anything about West Nile virus, this is going to sound familiar. The virus infects mosquitoes, which feed on birds, infecting them in the process.

With EEE, the mosquitoes involved in this cycle are called Culiseta melanura, which live in freshwater swamps and feed on songbirds. It's thought these mosquitoes feed almost exclusively on birds.

At a point – generally from July onward – there's enough of the virus in the mosquitoes and birds in a spot that it spills over into other populations. Different kinds of mosquitoes – some Culex mosquitoes that can transmit West Nile virus, for instance – feed on infected birds and pick up the virus. These different mosquitoes, known as bridging vectors, can then draw other species such as humans into EEE's web.

Once an area has had frost, mosquito activity drops off, and the virus effectively goes dormant until the next spring. Weaver said along the Gulf Coast, where hard frosts are uncommon.

Why more spillovers happen some years than others are not certain.

Climatic conditions likely play a role ; Weaver said.

Many of the studies look at the virus' life cycle are decades old, and may not fully reflect the current circumstances.

"A lot of our understanding of the basic enzootic transmission cycle comes from being done more than 60 years ago," Weaver said.

When EEE spills out of its mosquito-songbird cycle, which species does it infect? ​​

The second E of EEE is a clue. The first known outbreaks of eastern equine encephalitis actually occurred in the 1800s in horses – long before what the disease was discovered in the 1930s.

Deer, therefore, on the occasion of dogs. But these other animals, like humans, are considered dead-end hosts in the EEE transmission cycle.

The virus is very dangerous for horses and they may be vaccinated against it in places where [EEE is known to spread]

If horses can be vaccinated against EEE, can people?

Not unless you are a researcher studying EEE. Weaver and some other scientists who study the dangerous virus have been vaccinated with an unlicensed vaccine.

Multiple experimental EEE vaccines for people have gone through the preliminary stages of development, but because cases are so uncommon, there is not a human market for EEE vaccine. Given the very high cost of developing, testing and licensing a vaccine – North of $ 1 billion – without a market there is no chance one gets made.

Darci Smith, an arbovirus expert and Chief of the immunodiagnostics department at the Naval Medical Research Center at Fort Detrick, Md., Brought West Nile virus to make that point.

When West Nile was first found in North America in 1999, there was deep concern. And in a number of years since, there have been cases in the thousands. Like EEE, West Nile can cause severe illness and death. In fact, it was believed to have killed more than 2,000 Americans between 1999 and 2016.

Sanofi (SNY) Pasteur began to develop a West Nile vaccine, and eventually shelved the project after that concern to guarantee sales.

"And there's still no licensed [West Nile] vaccine," Smith said.

If there are no business prospects for a vaccine, why does EEE vaccine work continue?

The Department of Defense sees EEE as a potential biological weapon threat because of the severity of disease it causes and its high case fatality.

But for the Pentagon's interest, there would be little EEE research, Weaver and others said.

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