Rapid spread of chikungunya virus following its resurgence during 2006 in West Bengal, India.

Re-emergence of chikungunya virus (CHIKV) in West Bengal was detected after almost 40 years when an outbreak of fever occurred in Baduria village (West Bengal, India) in October 2006. The symptoms of CHIKV infection are similar to those of dengue virus (DENV) infection. Serum samples were tested for detection of IgM antibody to CHIKV and DENV and the aetiological agent was detected as CHIKV. RT-PCR was carried out for confirmation of CHIKV infection. By 2009, CHIKV had spread rapidly within ten districts of West Bengal. Middle-aged women (age group 31-40 years) were predominantly affected. Here we report the analysis of 2134 serum samples collected during 2006-2009 from the different districts of West Bengal, among which IgM antibody to CHIKV and DENV was detected in 403 and 199 samples, respectively. This report highlights the gradual dominating activity of CHIKV with dengue-like clinical features in dengue-endemic regions such as West Bengal.