Evaluation of chikungunya virus infection in children from India during 2009-2010: A cross sectional observational study

Chikungunya virus, a small (about 60–70 nm diameter), spherical, enveloped, positive, single stranded RNA virus is transmitted by Aedes mosquitoes. After a short period of incubation (3–5 days) symptoms like fever with joint pains and others start appearing. After a gap of 20 years, this virus re‐emerged during 2006–2008 in India causing a major outbreak of CHIKV in India. This study was conducted subsequent to the major outbreak in order to evaluate the proportion of chikungunya virus infection in children with suggestive symptoms at three geographical locations of India. Lineage of circulating strains and changes in the E1 structural polypeptide were also determined. Blood samples were collected (in Sodium citrate vacutainer tubes) during 1st June 2009 to 31st May 2010 from children (age 0 ≤ 18 years) suspected to have chikungunya infection, that is, those who presented with sudden onset of fever and/or joint pain, myalgia, and headache from three regions of India, All India Institute of Medical Sciences (AIIMS) in New Delhi, Karnataka Institute of Medical Sciences (KIMS) in Hubli and Sawai Mansingh Medical College (SMS) in Jaipur. Detection of CHIKV antibodies in all acute‐phase patient plasma samples was done by IgM ELISA and for samples within ≤5 days of fever, a one‐step RT‐PCR was carried out on a block thermo‐cycler targeting 294 bp region of E1 gene that codes for the viral envelope protein. Comparison of nucleotide and amino acid sequences from few positive samples of two regions was done with African S‐27 reference strain using BioEdit. A phylogenetic tree was constructed using MEGA 6 by using the Maximum Likelihood method based on the Kimura 2‐parameter model. Out of the 723 acute phase samples tested from three geographical locations of India, Chikungunya virus infection was detected in 249/723 (34.44%) subjects by either IgM Elisa (180/723) or RT‐PCR (69/412). RT‐PCR was employed in samples collected from children with ≤5 days of fever. Maximum positive cases were from KIMS center, Hubli. Seasonally, positivity varied with number of enrolled cases at KIMS and SMS. Joint pain was significantly associated with CHIKV positivity (P = 0.0156). Presence/absence of certain clinical features varied with age (P