95: Chikungunya Fever

Classification: ICD-9 066.3; ICD-10 A92.0

Syndromes and synonyms: Chikungunya means ‘that which bends up’ in Makonde language, to describe the pain.

Agent: Chikungunya virus (CHIKV), an enveloped RNA virus, genus Alphavirus in the family Togaviridae. CHIKV belongs to the same antigenic complex as Mayaro, Ross River, and o’nyong-nyong viruses. Phylogenetic analysis suggests an African origin about 500 years ago, with spread to Asia within the last century.

Reservoir: Non-human primates in Africa and humans in Asia; Asian monkeys can be infected, but do not seem to constitute an important reservoir. During intra-epidemic periods, several vertebrates have been implicated as potential reservoirs.

Vector: In Africa, the principal vectors are the sylvan mosquitoes Ae. furcifer and Ae. africanus, Ae. luteocephalus, and Ae. taylori; in Asia, urban Ae. aegypti, Ae. albopictus, and various Culex species.

Transmission: By mosquito bite. Transmission from mother to neonate can occur in the intrapartum period; blood-borne transmission is possible.

Cycle: Humans are viremic at a titer high enough to infect mosquitoes for 3 to 7 days post illness onset. The virus travels from the mosquito gut to the salivary glands in 5–7 days, after which it can infect another human by bite.

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