The Centers for Disease Control and Prevention (CDC) is closely following new reports of the mosquito-borne chikungunya virus among residents of the French side of St. Martin in the Caribbean. While outbreaks of chikungunya have been reported in some parts of Africa, Europe, Asia and the Pacific, this marks the first time the disease has been reported among non-travelers in the Western Hemisphere.
The World Health Organization has reported 10 confirmed cases on the island. Testing to confirm other suspected cases is ongoing. Chikungunya virus is transmitted by the same mosquitoes that spread dengue virus (Aedes aegypti and Aedes albopictus); these mosquitoes are widely found in the Caribbean and the tropics.
The affected St. Martin residents had not traveled recently, suggesting that chikungunya virus is now present in island populations of mosquitoes and is being spread locally. Further spread on St. Martin, to other Caribbean islands, and to the surrounding mainland areas is possible in the coming months and years. The mosquitoes that spread it are also found in some areas of the United States.
“Microbes know no boundaries, and the appearance of chikungunya virus in the Western hemisphere represents another threat to health security,” says CDC director Tom Frieden, MD, MPH. “CDC experts have predicted and prepared for its arrival for several years and there are surveillance systems in place to help us track it. To protect Americans, we have to support and maintain capacity to detect and respond to the emergence of new viruses."
CDC has been working since 2006 with the Pan American Health Organization (PAHO) and countries in the Americas to prepare for the arrival of chikungunya in the Americas. CDC and PAHO issued joint guidelines in 2011 to help establish regional response plans.
CDC also conducted a planning workshop for 22 Caribbean countries to build local capacity to detect and respond to cases of chikungunya and other mosquito-borne diseases. CDC trained laboratory staff from 10 regional reference labs in testing techniques for chikungunya virus.
A total of 109 laboratory-confirmed cases of chikungunya were identified in the United States from 1995 through 2009. All were in travelers, and all but three of them occurred between 2006 and 2009 when there were large outbreaks of the disease ongoing in India and Indian Ocean Islands. From 2006 through 2009, an average of 26 travel-related chikungunya cases was identified per year. None of the cases triggered a local outbreak in the United States.
CDC estimates that about 9 million U.S. residents travel to the Caribbean each year. Given that volume of travelers, chikungunya could occur more frequently in returning U.S. mainland travelers if the virus expands in the region. Infected travelers could then cause local transmission of the virus in the United States if mosquitoes bite infected people and then bite other people.
CDC has issued a travel health notice advising those planning to travel to St. Martin to take steps to protect themselves from mosquito bites. These steps include using insect repellent, wearing long sleeves and pants, and using air conditioning and screens on windows and doors to keep mosquitoes out.
Travelers returning from the Caribbean who experience fever and joint pains as well as other symptoms of chikungunya (e.g., headache, muscle pains, or rash) should seek medical care, and health care providers should be on the alert for possible cases. People infected with chikungunya should protect themselves from further mosquito bites during the first few days of illness, in order to prevent other mosquitoes from becoming infected and reduce the risk of further spread.
The term chikungunya comes from a word in the Makonde language (spoken in southeast Tanzania and northern Mozambique in Africa) and means “that which bends up,” because patients often are stooped in pain while suffering from the disease. The symptoms resemble those of dengue, another serious mosquito-borne infection that is common throughout the Caribbean islands.
Infection with chikungunya virus is rarely fatal but the joint pain seen with chikungunya can often be severe and debilitating. The virus is not spread person to person. There is no vaccine and no specific treatment for the infection. Patients recover in about a week, although long-term joint pain occurs in some people. Infection is thought to confer lifelong immunity.
For more information, visit: www.cdc.gov/chikungunya