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

Background: After the 2007 epidemic, a major outbreak of chikungunya was reported from Thiruvananthapuram, Kerala, India during 2019-2020. Study design: A cross sectional survey was conducted during the period to elucidate the clinical profile of patients and the genotype of CHIKV involved in the infections in one of the worst affected villages. Patients (n = 148) meeting WHO case definition were recruited both prospectively and retrospectively. All the samples were subjected to either RT-PCR or IgM ELISA based on the duration of symptoms. The CHIKV envelope gene sequences amplified among the positives were analyzed. Data on socio-demographic details, mosquito control practices, clinical features, details of hospitalization and treatment were collected. Results: Among the CHIKV suspected cases, 38 were recruited prospectively and 110 retrospectively. Among the former group 92% tested positive for CHIKV infection by either PCR or ELISA. Fever (51.4%) and joint pain (20.0%) were the presenting symptoms. More than 45% of the subjects had involvement of the knee joints. CHIKV Envelope gene sequence analysis indicated that all the cases belonged to the genetic lineage similar to 2006 outbreak CHIKV in Kerala. In addition, two novel non-synonymous mutations, K211E and I317V was recorded. Conclusions: The clinical presentation of Chikungunya has shown some changes compared to previous epidemic. Fever was reported to be the initial symptom of the clinical profile. Implication of the two additional mutations found in the envelope gene of the virus needs further exploration towards recent increasing trend of CHIKV infection in the state.