A widespread unknown fever broke out in nine districts of West Bengal, from August 2007, that continued up to December 2007. A total of 800 patients were investigated and 321 (40.13%) were found to be reactive for Chikungunya antibodies by IgM capture ELISA and HI test. 66% of the patients were male. Predominant signs & symptoms observed in the sero-positive cases were fever (100%), arthralgia (96%) and diffuse erythematous rash(94%). 3% of the patients had hemorrhagic manifestations. Four suspected deaths occurred.
