Re-emergence of chikungunya virus in India.

Chikungunya virus is no stranger to the Indian sub­ continent. Since its first isolation in Calcutta, in 1963, there have been several reports of chikungunya virus infection in different parts of India. The last outbreak of chikungunya virus infection occurred in India in 1971. Subsequently, there has been no active or passive surveillance carried out in the country and therefore, it ‘seemed’ that the virus had ‘disappeared’ from the subcontinent. However, recent reports of large scale outbreaks of fever caused by chikungunya virus infection in several parts of Southern India have confirmed the re-emrgence of this virus. It has been estimated that over 1,80,000 cases have occurred in India since December 2005. Andhra Pradesh (AP) was the first state to report this disease in Deccmber 2005, and one of the worst affected (over 80,000 suspected cases). Several districts of Karnataka state such as Gulbarga, Tumkur, Bidar, Raichur, Bellary, Chitradurga, Davanagere, Kolar and Bijapur districts have also recorded large number of chikungunya virus related fever cases. Over, 2000 cases of chikungunya fever have also been reported from Malegaon town in Nasik district, Maharashtra state, India between February-March 2006. During the same period, 4904 cases of fever associated with myalgia and headache have been reported from Orissa state as well. According to the National Institute of Virology, Pune, out of 362 samples collected from different places in AP such as Kadapa, Secunderabad, Chittoor, Anantapur, Nalgonda and Prakasam, Kurnool and Guntur districts, 139 were found positive for chikungunya, antibodies, six for dengue fever and 15 related to both the fevers. Apart from India, several small countries in the southern Indian Ocean such as the French Reunion Islands, Mauritius, Seychelles and other countries have also been reporting large scale outbreaks of chikungunya virus infection this year.