A holiday trip to the Caribbean could lead to infection with a virus brand-new to the Americas, the CDC is warning.
The mosquito-borne chikungunya virus -- pronounced chik-un-GUHN-ya -- is widespread in Asia and Africa and is considered endemic in some regions.
But until now cases in the Americas have been imported by travelers, rather than being homegrown infections.
That changed this month, according to the World Health Organization, when investigation of possible dengue fever in St. Martin turned up two confirmed, four probable, and 20 suspected cases of chikungunya.
Importantly, the CDC noted, the affected people had not traveled, implying there is -- for the first time -- local transmission of the virus in the Americas.
Symptoms include high fever and headache, with significant joint pain that can persist for several weeks. The symptoms appear within 7 days of a person being bitten by an infected mosquito.
The insects involved are usually Aedes aegypti and Ae. albopictus mosquitoes, which also spread dengue fever, the CDC and WHO noted in a 2011 report on the possibility of chikungunya coming to the region.
After the WHO report of chikungunya in St. Martin, the French half of the Caribbean island, the CDC warned travelers to protect themselves from mosquito bites by using insect repellent, wearing long sleeves and pants, and using screens on windows and doors to keep mosquitoes out.
"Microbes know no boundaries, and the appearance of chikungunya virus in the Western hemisphere represents another threat to health security," CDC Director Tom Frieden, MD, said in a statement.
He noted that the agency had predicted the virus would arrive sooner or later. The 2011 paper, titled "Preparedness and Response for Chikungunya Virus: Introduction in the Americas," reported that Asia and Africa have been seeing epidemics of "unprecedented magnitude" in recent years.
And the number of travelers returning to the U.S. with the disease has been growing -- from just three laboratory-confirmed or probable cases between 1995 and 2005 to 106 from 2006 through 2009.
None of the imported cases has so far triggered local transmission in the U.S., the CDC said, but the mosquitoes involved are found in some states.
The agency said it estimates that about nine million people travel from the U.S. to the Caribbean annually. If the chikungunya virus spreads more widely in the region, it could occur more often in returning travelers and that could lead to local transmission in parts of the U.S.
There is no specific treatment for the virus and no vaccine.
The 2011 CDC/WHO report noted that the "only available method" to prevent or slow a possible epidemic is control of the mosquitoes that carry the virus.
But mosquito control, the report said, "has rarely been achieved and never has been sustained."
The name of the virus comes from a word meaning "that which bends up" in the Makonde language of southeast Tanzania and northern Mozambique.
That's because patients are often stooped or bent in pain.
The virus is rarely fatal but the joint pain is often severe and debilitating, the CDC noted.
The agency also said the virus is not spread from person to person, patients usually recover after a week although some may have long-lasting joint pain, and infection is thought to confer lifelong immunity.