Mosquito-Borne Virus Now in U.S. Territory

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Mosquito-Borne Virus Now in U.S. Territory

News Review from Harvard Medical School

June 13, 2014

News Review From Harvard Medical School -- Mosquito-Borne Virus Now in U.S. Territory

A case of the mosquito-borne virus chikungunya has been reported for the first time in a U.S. territory. The virus was acquired in the U.S. Virgin Islands, health officials there said. A second patient acquired the infection elsewhere, they said. The virus mostly has been found in Africa and Asia. But it has been spreading rapidly across the Caribbean in recent months. More than 135,000 suspected and confirmed cases have been reported in the Western Hemisphere since December. This is the first case anywhere in the United States. But health officials are concerned that it will spread to the mainland soon. The 2 types of mosquitoes that spread chikungunya are also found in southern and eastern U.S. states. Symptoms of chikungunya include a high fever, headaches and severe pain in joints. The virus is rarely fatal, but symptoms can linger for months. There is no vaccine. The Associated Press and wrote about the virus June 12.


By Mary Pickett, M.D.
Harvard Medical School


What Is the Doctor's Reaction?

A couple of months ago, one of my most uncomplaining of patients came in to clinic several times. She had terrible aches throughout her body. One of my colleagues thought she might have a common problem called polymyalgia rheumatica (PMR). He put her on prednisone. But this did not solve the problem.

She continued to ache and she went on to have severe headaches and spells of profound confusion. "I would stare at an e-mail for an hour and not know how to answer it," she told me. I diagnosed her with encephalitis, inflammation of the brain. This was starting to look more like a very bad infection. But from what cause?

I asked her about travel before her illness, and my eyes widened as she described fly-fishing trips to both South America and Central America.

I described some standard tests we would run. And then, "I think we should test you for one more virus," I told her. "The virus is called chikungunya."

It felt almost silly to order this test. Why? Because this is a virus that has never been found in the specific countries that she visited. For the last 50 years, chikungunya virus has existed only in Africa and Southeast Asia.

But this virus has been spreading across the map. Seventeen countries or territories in the Caribbean and South America have now had cases. Just yesterday, a first case was reported from the U.S. Virgin Islands. Also this week, a patient in North Carolina was diagnosed. This person had recently traveled to the Caribbean.

The U.S. Centers for Disease Control and Prevention (CDC) has asked doctors to be watchful for possible cases. This was the first time I had tested for chikungunya. But with its spread, I am sure it will not be the last.

Mosquitoes spread the infection. Some people think it is spreading because global warming is allowing mosquitoes to have a wider range.

My patient's chikungunya test just came back last week, and it was negative. I was relieved to give her this result, because the symptoms from this virus can last for many months. She is doing better after an antibiotic. As is the case with 60% of encephalitis cases, we probably will not ever figure out what caused her symptoms.


What Changes Can I Make Now?

I first heard about chikungunya virus in 2005 when there was a terrible epidemic on Reunion Island, near Madagascar. Within a year, roughly 20% of the entire island population had been infected. It was a memorable, awful-sounding disease. Chikungunya causes profound body aches. They can be lasting and disabling.  The name is from the Makonde language in Tanzania and Mozambique. It means "he who walks bent over."

It is not good news that this virus is spreading. Doctors need to be aware of the new presence of "chik" in the Western Hemisphere. It is not treatable. Only time heals a person who is infected. So our focus needs to be on prevention.

The mosquito has been named the most deadly non-human animal on the planet. Chikungunya has "upped the ante" in mosquito-bite prevention. You can get some bad, bad infections from mosquito bites, including West Nile virus, malaria and dengue fever. Chikungunya is rarely fatal. But because this virus can cause lasting symptoms and can be so severely painful, it ranks up there in importance with those other infections.

So far, chikungunya is still rare in the Western Hemisphere. But I strongly recommend wearing insect repellant if you are in areas with significant mosquito biting. Long sleeves and long pants prevent bites. Bed nets create a helpful screen that can protect you from mosquitoes as well.

Even if you plan to use insect repellant, don't forget to talk with your doctor about malaria-prevention pills if you will travel to an area where malaria occurs.


What Can I Expect Looking to the Future?

It is expected that chikungunya will continue to spread. There will probably be cases in the southern United States within the next several years.

Several research groups are working to develop a vaccine against chikungunya, but no vaccine is currently available.

New strategies also are being researched related to mosquito control. One of the most creative strategies involves purposeful release of infertile male mosquitoes into the environment. Female mosquitoes are distracted by mating with these males, and over time the mosquito population diminishes.

Last updated June 13, 2014

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