Prevalence of respiratory syncytial virus group B genotype BA-IV strains among children with acute respiratory tract infection in Kolkata, Eastern India.

Background: Although recognized as a significant respiratory pathogen, there is a dearth of information on genetic diversity of human respiratory syncytial virus (HRSV) strains among children in India.

Objectives: To study prevalence and genomic diversity of HRSV strains among children (<5 years of age) with acute respiratory tract infection (ARTI) at Dr. B.C. Roy Memorial Hospital for Children, Kolkata, Eastern India.

Study Design: During September 2005 to August 2008, nasal and/or throat swabs from children with ARTI were screened for presence of HRSVs by RT-PCR of nucleocapsid (N) and glycoprotein (G) genes. Classification of G gene of HRSV strains were achieved with different primer pairs designed for amplification of N'- and/or C'-terminal hypervariable regions (HVR1 and HVR2) of HRSV A and B strains. The HVR1 and HVR2 of G gene of 27 and 22 HRSV B strains were sequenced.

Results: One hundred seventy seven of 1720 clinical samples were positive for HRSVs. Group B strains were detected at higher rates (95% against 5%, n=80) than A in 2005-2006, whereas in consecutive years, the rate of detection of group A were higher (94.84% against 5.16%, n=97). The group B strains were genetically related to globally spreading BA genotype, exhibiting conserved nature of stop codon, six nucleotide deletions in HVR1 and formed single phylogenetic clusters for both HVR1 and HVR2.

Conclusions: The detection of significant high rates of group B strains in 2005-2006 followed by increase in prevalence of A strains in subsequent years highlight the dynamic nature of prevalence of HRSV subtypes among children with ARTI in Eastern India.