The first case of chikungunya virus infection acquired within the continental U.S. has been reported by the CDC. The case was reported today in Florida in a male who had not recently traveled outside the U.S. the agency announced late Thursday.
The CDC added that it was working with Florida public health officials "to investigate how the patient contracted the virus" and would monitor for additional domestically acquired cases that may occur.
Although the virus has spread rapidly in the Caribbean islands, where it apparently originated, the CDC downplayed the risk of further movement into the continental U.S.
"CDC officials believe chikungunya will behave like dengue virus in the U.S., where imported cases have resulted in sporadic local transmission but have not caused widespread outbreaks," the agency said.
"None of the more than 200 imported chikungunya cases between 2006 and 2013 have triggered a local outbreak. However, more chikungunya-infected travelers coming into the U.S. increases the likelihood that local chikungunya transmission will occur."
As of this week, the region is reporting 4,576 confirmed and 165,990 suspected cases of the virus, for a total of 170,566, according to the Pan American Health Organization.
There have been 14 deaths, all in the French- and Spanish-speaking islands. The CDC is recommending that travelers to the Caribbean protect themselves from mosquito bites.
In the U.S., the CDC is reporting that 80 chikungunya cases have been reported to ArboNET, the national surveillance system for arthropod-borne diseases, from U.S. states and territories.
Puerto Rico has the largest number of cases, with 23, all a result of local transmission. Travelers returning from the Caribbean imported the other 57 cases reported by the agency.
Florida has 34 of those cases and Virginia six, but no other state has more than three. The total doesn't include a case reported by Tennessee and two reported by Rhode Island.
The virus -- pronounced chik-un-GUHN-ya -- is carried by mosquitoes, mainly Aedes aegypti and Aedes albopictus, which are widespread in the U.S.
Nevertheless, there is no indication yet of local transmission in the U.S., other than the cases in Puerto Rico. The virus is not a national notifiable disease but can be reported to ArboNET, although not all cases are.
Chikungunya is widespread in Asia and Africa, but until late last year, cases in the Americas were imported by travelers to those regions, rather than being homegrown infections.
That changed in December, when the World Health Organization reported that an investigation into possible dengue fever in St. Martin turned up two confirmed, four probable, and 20 suspected cases of chikungunya.
The patients had not traveled, suggesting they had been infected locally.
The PAHO defines a suspected case as a patient with acute fever greater than 38°C, severe arthralgia (joint pain) or arthritis that isn't explained by other conditions, and who lives in or has recently visited an epidemic or endemic area. Cases are said to be confirmed if there is also a positive lab test for the virus using any of several methods, the agency said.