Clinical and virological characteristics of patients during the outbreak of chikungunya in Thiruvananthapuram, Kerala, India, 2019–2020

•An outbreak of chikungunya fever cases occurred in Thiruvananthapuram District, Kerala during 2019–2020, after a gap of about one decade of the past wide spread epidemic in India.•The clinical and virological studies carried out indicated a change in the symptomology as well as occurrence of two non-synonymus (NS) mutations in the envelope gene of the CHIKV.•The implications of the two NS mutations needs to be elucidated to understand the evolutionary trends of the CHIKV to prevent future large epidemics of chikungunya fever in the country.