The Centers for Disease Control (CDC) announced July 8 that they have received reports of 153 cases of chikungunya in U.S. residents thus far in 2014. Puerto Rico has reported 14 cases acquired locally and the U.S. Virgin Islands have reported one. The remaining are imported cases, two in the Virgin Islands and the remaining 136 in the continental United States. In addition, five illnesses in non-residents are reported by the CDC.
Imported chikungunya cases, or "travel-associated" as the CDC prefers to call them, have been found in 32 states. Alabama and West Virginia have confirmed cases which have not yet been reported by the CDC. Florida has updated its total from the 34 cases on the CDC site to 66 chikungunya cases through July 5.
A compilation of state reports show that the continental U.S. has 42 more cases than in the CDC report. Florida leads the nation in total chikungunya illnesses and 96 percent were acquired in either Haiti or the Dominican Republic. California and Tennessee follow with ten reported illnesses each.
This period's reporting was affected by the July 4 holiday weekend. The Pan American Health Organization reported in its June 27 statement that Puerto Rico had 20 confirmed chikungunya cases and 119 suspected cases. It shows three confirmed cases in the Virgin Islands. Both differ from the CDC report.
No locally acquired cases of chikungunya have been reported from the continental United States. For that to happen, the vector for the current strain must be present. If Aedes aegypti, the Yellow Fever mosquito, is not present in a region, the illness cannot be spread.
The Centers for Disease Control describe the transmission of chikungunya this way:
Chikungunya virus is transmitted to people through mosquito bites. Mosquitoes become infected when they feed on a person already infected with the virus. Infected mosquitoes can then spread the virus to other people through bites.
It is not contagious and cannot be spread other than through the bite of an already infected mosquito. Travel-acquired chikungunya illnesses are those diagnosed in the United States but the patients contracted the illness out of the country. The potential for a local outbreak of chikungunya exists where the mosquito vector exists. A timeline of yellow fever outbreaks in the United States put together by PBS notes that summer epidemics have been seen in places as diverse as Boston in 1693, New York City in 1702 and New Orleans in 1853.
Aedes aegypti makes its habitat in tropical and sub-tropical climates. It feeds, almost exclusively, on humans and other primates. It is considered an urban mosquito, living closely to its source of blood. Blood is vital to the reproductive process of the insect.
It is a container mosquito. It will lay eggs in any source of still, fresh water such as an unused pool or abandoned tire. Mosquito control for the Yellow Fever mosquito consists of a number of tactics, including draining or dumping cans, tires, bird baths and other containers that can serve as a breeding ground.