Chikungunya is an arbovirus transmitted by Aedes mosquitoes, causing viral arthritis, fever, and rash. Infection is generally mild, but in rare cases patients can develop severe and fatal complications. Outbreaks have occurred in Africa, Asia, the Indian subcontinent, and the Americas, with no treatment or vaccine available. In March 2005, the first case of chikungunya was reported on Réunion island, an overseas department of France located off the coast of Madagascar in the Indian Ocean. The Regional Department of Health and Social Affairs (DRASS) declared the disease to be nonfatal and projected the epidemic to be over by the end of July 2005. However, the epidemic persisted until April 2007 with a total of 266,000 infections, nearly one third of the island’s population, and 250 deaths reported. To understand how a seemingly mild and controllable epidemic persisted for much longer than it should have, we must look beyond infectious disease biology and epidemiology.

Contributed by Mika O’Shea