Week 11 ~ Chikungunya May Soon Say Hello to the U.S.

I had never heard of Chikungunya until this semester's epidemiology class. This is probably because the viral disease mainly occurs in Africa, Asia, and the Indian subcontinent. Today, chikungunya has been identified in nearly 40 countries in Asia, Africa, Europe, and in late 2013, the Chikungunya virus was found for the first time in the Americas on islands in the Caribbean (CDC, 2014; WHO, 2014). Now there is concern that this disease may soon make its way into the United States.

Chikungunya is a viral disease transmitted to humans by the bites of infected female mosquitoes. There is no medicine to treat this disease, so treatment is focused on relieving the symptoms: "Chikungunya is characterized by an abrupt onset of fever frequently accompanied by joint pain. Other common signs and symptoms include muscle pain, headache, nausea, fatigue and rash" (WHO, 2014). Symptoms usually begin within 3-7 days after being bitten by an infected mosquito. Most patients start to feel better within a week or two after symptoms appear and will fully recover, but the joint pain (which can be very severe and debilitating) may continue for weeks or even months (CDC, 2014). But the good news is, once you are infected you become immune to the virus.

The first documented outbreak of chikungunya with autochthonous (native) transmission in the Americas occurred in December 2013: France reported 2 laboratory-confirmed cases of the disease in the French part of the Caribbean island of St. Martin. Since then, there have been confirmed cases of local transmission in the Dutch part of St. Martin, Anguilla, British Virginia Islands, and a few other islands (WHO, 2014). According to Rob Quinn's online article for USA Today (2014), there have now been more than 25,000 cases reported in the Caribbean region as of mid-April. There have also been reported cases in French Guiana, a French region on the northeast coast of South America. Public health officials suspect the virus may already be in Puerto Rico, and they believe it could spread to the southern United States within months (McGowan, 2014).

Aedes aegypti - Yellow Fever Mosquito

In her article (2014), McGowan includes a quote by Kristy Murray from Baylor College of Medicine: "We have cruise ships coming in every day [from the Caribbean]. We have the vectors here and the perfect conditions for spread."

I completely agree with this statement. The Caribbean is a very popular place to travel on a cruise, so the risk of Americans being bitten and becoming infected seems somewhat high. However, the strain of chikungunya that is spreading in the Caribbean is most commonly transmitted by Aedes aegypti, the yellow fever mosquito. This species can only survive in the warmest parts of the country: Alabama, Florida, Georgia, Louisiana, Mississippi, South Carolina, southern Texas, as well as parts of southern Arizona and a few California cities (McGowan, 2014). This could definitely limit transmission, which is good news if the virus does end up spreading into the U.S.

Aedes albopictus - Asian Tiger Mosquito

In other outbreaks around the world a different strain of the chikungunya virus was carried by Aedes albopictus, the Asian tiger mosquito. This is a very invasive species which first appeared in Houston in the 1980s. It is now found from Illinois to New York, meaning it can survive in colder environments unlike the yellow fever mosquito. Right now, researchers do not know whether the Asian tiger mosquito can efficiently transmit the chikungunya strain that is currently circulating in the Caribbean (McGowan, 2014). If it can, though, the disease could easily travel very far past the southern states.

Prevention is definitely a key component when dealing with the current outbreaks and the possible spreading of the disease to the U.S. Although an infected individual cannot directly transmit the virus to another human, the risk of spreading the disease is greater when infected and non-infected people don't take precautions. People traveling to chikungunya-affected areas should take extra precautions because they could end up being the ones who start a U.S. outbreak. Wearing mosquito repellent and covering up as to not expose a lot of skin can definitely decrease the chance of being bitten by an infected mosquito. People who have already been infected in the past should not be any less cautious. Although they cannot contract the disease again, they can still be bitten and carry the virus, increasing the chance of infecting other mosquitoes who may bite them. This then increases the number of infected mosquitoes, which of course will raise the risk of spreading the disease.

References
1. Centers for Disease Control and Prevention. (2014). Chikungunya virus. Retrieved from http://www.cdc.gov/chikungunya/
2. Quinn, R. (2014). Next stop for Chikungunya virus: The U.S.? USA Today. Retrieved from http://www.usatoday.com/story/news/nation/2014/04/22/newser-chikungunya-virus/8003463/

3. World Health Organization. (2014). Chikungunya. Retrieved from http://www.who.int/mediacentre/factsheets/fs327/en/ 

4. McGowan, K. (2014). Chikungunya, a highly infectious disease, may soon arrive in the U.S. Al Jazerra America. Retrieved from http://america.aljazeera.com/articles/2014/4/21/chikungunya-a-highlyinfectiousdiseasemaysoonarriveintheus.html

5. Photo (top): http://www.cdc.gov/chikungunya/image/maps/CHIK_Americas_Larger_Area_Map.gif

6. Photo (2nd from top): http://images.medicinenet.com/images/government/yellow-fever-mosquito.jpg 

7. Photo (2nd from bottom): http://upload.wikimedia.org/wikipedia/commons/e/ea/Aedes_Albopictus.jpg

8. Photo (bottom): http://cdn2-b.examiner.com/sites/default/files/styles/image_content_width/hash/77/0b/770bee3b72379afd48446ce3536977e4.jpg?itok=j-3TzAxG