In 2005, a strain of the Chikungunya virus that arose in east Africa spread to the islands of Comoros, Mayotte, Seychelles and Reunion in the south-western Indian Ocean.
Later that year, the virus began to cause large-scale outbreaks in India.
Links:
[1] http://admin.indiaenvironmentportal.org.in/news/two-mutations-factor-chikungunya
[2] http://admin.indiaenvironmentportal.org.in/category/newspaper/hindu-new-delhi
[3] http://admin.indiaenvironmentportal.org.in/category/thesaurus/chikungunya
[4] http://admin.indiaenvironmentportal.org.in/category/thesaurus/vector-borne-diseases
[5] http://admin.indiaenvironmentportal.org.in/category/thesaurus/health-care
[6] http://admin.indiaenvironmentportal.org.in/category/thesaurus/global