Chikungunya infection in India: results of a prospective hospital based multi-centric study

Abstract

Background: Chikungunya (CHIKV) has recently seen a re-emergence in India with high morbidity. However, the epidemiology and disease burden remain largely undetermined. A prospective multi-centric study was conducted to evaluate clinical, epidemiological and virological features of chikugunya infection in patients with acute febrile illness from various geographical regions of India.

Methods and findings: A total of 540 patients with fever of up to 7 days duration were enrolled at Karnataka Institute of Medical Sciences (KIMS), Karnataka (South); Sawai Man Singh Medical College (SMS) Rajasthan (West), and All India Institute of Medical Sciences (AIIMS) New Delhi (North) from June 2008 to May 2009. Serum specimens were screened for chikungunya infection concurrently through RT-PCR and serology (IgM). Phylogenetic analysis was performed using Bioedit and Mega2 programs. Chikungunya infection was detected in 25.37% patients by RT-PCR and/or IgM-ELISA. Highest cases were detected in south (49.36%) followed by west (16.28%) and north (0.56%) India. A difference in proportion of positives by RT-PCR/ELISA with regard to duration of fever was observed (p<0.05). Rashes, joint pain/swelling, abdominal pain and vomiting was frequently observed among chikungunya confirmed cases (p<0.05). Adults were affected more than children. Anti-CHIK antibodies (IgM) were detected for more than 60 days of fever onset. Phylogenetic analysis based on E1 gene from KIMS patients (n = 15) revealed ∼99% homology clustering with Central/East African genotype. An amino acid change from lysine to glutamine at position 132 of E1 gene was frequently observed among strains infecting children.

Conclusions: The study documented re-emergence of chikungunya in high frequencies and severe morbidity in south and west India but rare in north. The study emphasizes the need for continuous surveillance for disease burden using multiple diagnostic tests and also warrants the need for an appropriate molecular diagnostic for early detection of chikungunya virus.

Figure 1. Proportion of CHIKV-positivity by RT-PCR or IgM ELISA according to days of fever onset.

n denotes the total number of CHIKV positive cases.

Figure 2. Age distribution of chikungunya patients at hospitals in Karnataka and Rajasthan, June 2008 through May 2009.

Figure 3. Phylogenetic analysis of the E1 gene (nt 10246 to 11158) of chikungunya strains from adults (shown in closed circles) and children (shown in straight closed triangles).

The tree was constructed using the neighbor-joining method with 1000 bootstrap resamplings and rooted with the E1 gene of the O'nyong-nyong virus. Reference sequences were obtained from the GenBank and EMBL databases; accession numbers are given in parentheses.