Chikungunya, a tropical disease transmitted by the aedes mosquito, is characterised by fever, headache, rashes, and debilitating arthralgia. Chikungunya was believed to be a non-fatal and self-limiting disease, but recently a severe form of the disease with CNS involvement and fulminant hepatitis has been reported on the Indian Ocean island of Réunion. By March, 2006, a third of the population was affected and the disease had caused 237 deaths. 1 Asia reported its first outbreak of chikungunya virus in Thailand in 1958. In 2001–2003, chikungunya virus re-emerged in Java, Indonesia, after a gap of 20 years. 2 The first reported outbreak of chikungunya in India was in Calcutta city in 1963 and the last outbreak occurred in Barsi in 1973. 2 The virus re-emerged in India in December, 2005, and is spreading continuously. The Indian government has reported 1 391 165 suspected chikungunya virus cases in 12 states in the country. 3 We feel this is a gross underestimate because no systematic surveillance system for chikungunya virus existed until August, 2006, there are only two laboratories for virological testing for the whole country, and most private doctors do not report cases of the disease.

Scientists at the National Institute of Virology of India reported that the outbreaks of chikungunya virus in 1963 and 1973 were of an Asian genotype, whereas the recent outbreaks are of an African genotype similar to the strain of virus found in the Réunion epidemic. 4 A mutation in the chikungunya virus that improves its ability to invade mosquito cells and to replicate has been reported. It has also been speculated that the virus might have acquired a higher neurovirulence leading to unusually severe cases. 1 In Ahmedabad, India, private doctors have reported complications and severe cases of chikungunya virus with involvement of the CNS and the renal system. Since August, 2006, various state governments have set up special mechanisms for reporting fever cases with joint pains. Major efforts were mounted for mosquito control including insecticide fogging and larvicidal measures. The print media and television have launched public awareness campaigns. Some states and city health departments have reported systematic surveys of mosquito breeding, which have been carried out by teams who go from house to house in selected areas. 5 Many non-governmental organisations and private doctors have also organised