Comparative evaluation of real-time PCR and conventional RT-PCR during a 2 year surveillance for influenza and respiratory syncytial virus among children with acute respiratory infections in Kolkata, India, reveals a distinct seasonality of infection.

Acute respiratory tract infections (ARTIs) are one of the most common causes of morbidity and mortality in young children worldwide. Influenza virus and respiratory syncytial virus (RSV) are the predominant aetiological agents during seasonal epidemics, and thus rapid and sensitive molecular tests for screening for such agents and timely identification of epidemics are required. This study compared real-time quantitative PCR (qPCR) with conventional RT-PCR for parallel identification of influenza A virus (IAV) or influenza B virus (IBV) and RSV. A total of 1091 respiratory samples was examined from children with suspected ARTIs between January 2007 and December 2008. Of these, 275 (25.21 %) were positive for either influenza or RSV by qPCR compared with 262 (24 .01%) positive by RT-PCR. Overall, IAV, IBV and RSV were detected in 121 (11.09 %), 59 (5.41 %) and 95 (8.71 %) samples, respectively. In spite of overlapping clinical symptoms, RSV and influenza virus showed distinct seasonal peaks. IAV correlated positively and RSV negatively with rainfall and temperature. No distinct seasonality was observed in IBV infections. This is, to the best of our knowledge, the first report of a systemic surveillance of respiratory viruses with seasonal correlation and prevalence rates from eastern India. This 2 year comparative analysis also confirmed the feasibility of using qPCR in developing countries, which will not only improve the scope for prevention of epidemics, but will also provide crucial epidemiological data from tropical regions.