A severe outbreak of Chikungunya fever has been reported at La Réunion Island (France) in 2005-2006. Chikungunya is a viral disease. Chikungunya virus is an alphavirus transmitted to humans by the bite of infected mosquitoes, usually of the genus Aedes (Aedes albopictus in La Réunion).

To date, more than 266,000 cases were estimated to have occurred in the island (760,000 inhabitants). Most of cases are expressed as a mild disease, with intense fever and arthralgias, with rare but serious complications (encephalitis, liver, cardiac or renal failures.) having required a hospitalization in an intensive care unit. 273 of such serious cases (immediately life threatening condition) have been reported among the cases, in patients aged over 10 days (59% were 65+ age old). Chikungunya was proven in 246 serious cases; 101 patients had comorbidities, and 27% of confirmed cases eventually died. In addition 44 cases of mother-to-child infections were reported and 40 were confirmed (one died).

To date, in 248 death certificates, chikungunya was reported as the direct or indirect cause of death, with a median age of 79, range 0-102, and a sex-ratio (M/F) of 0.95. InVS, in collaboration with Inserm (French NIH) also reported (by June 6, 2006) a significant excess of mortality (from all causes) during the major outbreak which occurred from December, 2005 (+10%) to April, 2006 (10.1%), with a peak of excess mortality reached in February (+34.4%), concommitant to the peak of incidence.

Today, there is no antiviral treatment against Chikungunya. We showed from ex-vivo studies (in a sensitive model of cells culture to the viral infection) that chloroquine provides a significant inhibition on the replication of the Chikungunya virus. This efficacy seemed also to be reached at a plasmatic concentration of similar order of magnitude as recommended for treating malaria with this drug.

This trial aims to assess efficacy and safety of chloroquine as as therapeutic treatment of chikungunya disease.