Chikungunya — In Your Back Yard?

Chikungunya (CHIK) fever is an acute illness that is caused by an alphavirus and transmitted to humans through the bite of an infected mosquito — usually of the genus Aedes. First recognized during an outbreak in 1952, the disease is characterized by sudden onset of fever, headache, severe joint pain, myalgia, and malaise occurring 2–4 days following a bite. Skin rash occurs in about 50% of cases. The infection is almost always self-limited, lasting 3–7 days. Diagnosis is by PCR demonstration of CHIK virus RNA, or by detection of IgM antibodies or rising neutralizing antibodies to CHIK virus.

During 2005–2006, twelve cases were diagnosed in individuals arriving in the U.S. from areas known to be epidemic or endemic for CHIK fever. The CDC has described four such cases (U.S. residents returning from Somalia and Kenya, Zimbabwe, and the Indian Ocean island of Réunion; and a traveler from India). All four patients showed the classic symptoms, and two had a rash. These cases were confirmed serologically; only one of the patients had detectable viral RNA. An editorial note points out that no known mosquito-borne CHIK virus transmission has occurred outside of endemic areas. However, such transmission is possible from travelers with high-grade viremia because the mosquito vector is widely present in tropical and temperate areas. No drug therapy is available; mosquito control and protection are the keys to prevention.

Researchers in France have detailed five cases of CHIK fever — four in travelers returning from Indian Ocean islands in early 2006 and one in a nurse who had direct contact with blood from an infected traveler. Virologic studies identified a new CHIK virus variant, recently emerged from the East/Central African lineage.