disease, human conditions, microbes

The Chikungunya Virus is in the U.S.: Get to Know the Virus

Have you heard of the chikungunya virus? The virus (pronounced chik-en-gun-ye) was discovered in 1952 in Africa, and has been slowly making its way around the world… although the pace has been quickened in recent years. The first U.S. case was reported just earlier this month, on July 17, 2014, and a second case soon followed it, so the virus is definitely in the country now.

Aedes aegypti mosquito biting chikungunya
The yellow fever mosquito (Aedes aegypti) is one of the two mosquito species that can transmit the chikungunya virus. (Image credit: Centers for Disease Control and Prevention)

Luckily, the infection is not usually fatal, but can be extremely painful and debilitating. The virus, which is spread by certain mosquitos from person to person, primarily causes a fever and joint pains in 4 to 7 days after being bitten, but other symptoms include headaches, joint swelling, muscle aches, and rashes. (The virus’s name, “chikungunya,” actually means “that which bends up” in an African language because of how people bend up due to joint pains.)

While the virus was first discovered in Tanzania in 1952 (likely from infected chimpanzees), it’s thought there may have been a recorded outbreak in 1779 (which agrees with genetics studies that place it as having evolved around 1700). Since its discovery, there have been occasional outbreaks in Africa, Southeast and South Asia, and Europe. In late 2013, cases appeared in the Western Hemisphere for the first time from local mosquitos — this was in South America and the Caribbean islands, with over 20 countries reporting cases.

In the U.S., travelers have brought the virus back from overseas, with 28 international travelers being infected on average each year from 2006 to 2013. These numbers skyrocketed since the virus made its way to mosquitos in the Western Hemisphere — since the beginning of the year, there’ve been 87 cases in the U.S. (as of July 19, 2014), mainly from people who had traveled to the Caribbean (primarily Puerto Rico). But there had not been any cases from local mosquitos (in people who had not traveled internationally) until July 17, 2014, when a person in Florida contracted the virus. There has been a second locally-transmitted Florida case since then, so it is clear that the virus is living in the state’s mosquitos. However, the Centers for Disease Control and Prevention (CDC) does not think the chikungunya virus will have a widespread outbreak in the U.S. (although over half of the states have now had cases — to see if your state is one of them, check out this map of chikungunya virus cases in the U.S.).

Sustained transmission of the virus is somewhat limited by the mosquitos that can spread it. It’s carried by two mosquito species, the yellow fever mosquito (Aedes aegypti) and the Tiger mosquito or forest mosquito (A. albopictus). Both of these mosquitos are found in the southeastern U.S. and parts of the Southwest U.S., and the Tiger mosquito is also found north along the East Coast and lower Midwest. (Interestingly, the virus was only carried by the yellow fever mosquito until 2006, when it met up with the Tiger mosquito on a small island east of Madagascar and underwent a small mutation to be able to be transmitted by the Tiger mosquito too.)

Because there is no vaccine for the virus, and no specific treatment when a person becomes infected, if you’re in an area where there have been cases of chikungunya and don’t want to catch it yourself, it’s best to avoid getting bitten by mosquitos. (This means wearing long sleeves and pants, keeping secure screens on windows and doors that are open, getting rid of standing water to prevent mosquitos from reproducing nearby, and wearing insect repellent.) While most people who get it just have a fever and joint pains for a few days or weeks, a small percentage can have joint pains for months. It can also be more dangerous for people who are older (over 65 years old), pregnant, or have a medical condition.

So if you’re having second thoughts about whether you should take a moment to put on some mosquito repellent before going out on that evening walk, knowing that you could get more than just an itchy bump if a blood-sucking pest picks you for their dinner might help you make up your mind. (But really, while it’s not a real danger in the U.S. yet, you should definitely take precautions if you’re planning a trip to the Caribbean!)

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