(CHIKV) is a positive single-stranded RNA virus within the genus Alphavirus, family Togaviridae (1–3). In humans, CHIKV infection has a rapid onset and is typically cleared in 5–7 days. Following transmission, CHIKV replicates in the skin and then disseminates to the liver and joints. The incubation period for CHIKV infection is 2–4 days. Signs and symptoms of infection include high fever, rigors, headache, photophobia, and a petechial or maculopapular rash, and most infected persons also report severe joint pain (2–4). CHIKV is transmitted through the bite of infected Aedes aegyptiand Ae. albopictus mosquitoes. The current reemergence of CHIKV seems to be related to 1) CHIKV host switching from Ae. aegypti to Ae. albopictus mosquitoes, while retaining Ae. aegypti mosquitoes as a vector, and 2) introduction of Ae. albopictus mosquitoes, which were originally from Southeast Asia, into new areas of the world, including Africa. Severe epidemics of CHIKV infection have occurred in countries in the Indian Ocean region and Africa (1–3). We report an outbreak of CHIKV infection in Brazzaville, Republic of Congo, that was associated with the mosquito vectors Ae. albopictus and