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How concerned should we be about the mosquito-borne Chikungunya virus?

BY Jenny Marder  July 23, 2014 at 5:19 PM EST
The mosquito Aedes aegypti, with its distinctive markings in the form of a lyre, spreads disease like yellow fever and is a carrier of the Chikungunya virus. Photo courtesy Centers for Disease Control/Wikimedia Commons

The mosquito Aedes aegypti, with its distinctive markings in the form of a lyre, spreads disease like yellow fever and is a carrier of the Chikungunya virus. Photo courtesy Centers for Disease Control/Wikimedia Commons

On Thursday, federal officials announced that the tropical Chikungunya mosquito-borne disease had been transmitted for the first time within the United States, infecting two Florida residents.

What’s notable about these cases is that the people affected reported no recent trips to the Caribbean, Africa or Asia, where the painful virus is widespread. Until last week, all cases reported in the continental United States were from people who had recently traveled to endemic areas. Read: Chikungunya-infected mosquitoes are now living, breeding and sucking human blood in the continental United States.

“This is not good news,” said Mike Raupp, professor of entomology at the University of Maryland.

A few facts. The word Chikungunya derives from the Kimakonde language in Southeast Africa. (Click here for pronunciation.) It means contorted, a nod to the stooped-up appearance of people with severe joint pain, one of the main symptoms of the virus, along with fever, muscle pain, headache, fatigue and rash, according to the World Health Organization.

“Mainly, you’re going to get a fever,” said Walter Tabachnick of University of Florida’s Florida Medical Entomology Laboratory. “You’re going to feel lousy. With Chikungunya, you’re going to ache. You do not want to get this disease.”

It is seldom fatal. But that fact shouldn’t deter anyone from aggressive mosquito control, stressed Tabachnick, who believes the media has downplayed the danger of the virus.

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“No one wants to be a fearmonger. No one is saying, ‘We’re all going to die.’ But on the other hand, it does take public awareness and public responsibility to protect themselves. We’ve been very frustrated by the inability to get this message out to the public and nothing seems to take.”

The virus is primarily transmitted by two types of mosquitoes, the Aedes aegypti and Aedes albopictus, also known as the yellow fever and Asian tiger mosquitoes, respectively. Both are invasive to the United States. The yellow fever mosquito arrived in the 1500s; the Asian Tiger more recently, in the 1980s.

Unlike the West Nile virus, which is transmitted to mosquitoes mostly from birds and only occasionally to humans, Chikungunya is a mosquito-man virus. This means mosquitoes easily and efficiently transmit the virus to humans.

Transmission of the virus goes like this: A female mosquito bites an infected person. For about seven days, the virus incubates inside the mosquito, multiplying. The warmer the weather, the shorter that incubation period. Eventually, it migrates into the insect’s salivary glands, and as the mosquito feeds on human blood, she spits, transmitting the virus. (Note: only female mosquitoes bite. They need the protein in the blood to grow eggs.)

These mosquitoes prefer to breed in man-made storage containers: soda cans, birdbaths, rain barrels and garbage can lids. Standing water that collects on tarp-covered boats is a major breeding site in Florida, Tabachnick said. Yellow fever mosquitoes prefer these sites to natural water, like puddles.

As of July 18, 2014, a total of 436,586 suspected and 5,724 laboratory-confirmed Chikungunya cases had been reported in the Caribbean, Central America, South America and the United States, according to the Pan American Health Organization.

“This is not a trivial illness,” Raupp said. “Even though it’s not often lethal. What’s disturbing is we know we have vector-competent mosquitoes who are able to feed off someone who has a virus circulating in their bloodstream and to transmit it to people who have not yet traveled.”

To prevent breeding, he said, police and clean up your yard. Dump the birdbath twice a week. Dump or monitor other sources of water.

“The public outcry should be to demand your neighbors to clean up,” Tabachnick said. “All it takes is one property owner who doesn’t care, and he could be rearing enough mosquitoes to endanger the entire neighborhood.”

And a rule of thumb: apply insect repellant over sunscreen, not the other way around.