Influenza activity among the paediatric age group in Chennai.

BACKGROUND & OBJECTIVE Respiratory viral infections have a major impact on public health. Acute respiratory infections largely caused by viruses, are the most common illnesses experienced by otherwise healthy adults and children. Among the respiratory viruses, influenza viruses are known to cause outbreaks globally. Information on the activity of influenza virus in our country is limited and none from Chennai. The present study was carried out to isolate and identify the influenza virus serotypes causing acute respiratory infection in children attending a tertiary care centre at Chennai. METHODS During January to December 2002, 240 children with acute respiratory infection attending the out patient clinic of Institute of Child Health were included by convenient sampling. Throat swabs were collected from 4 to 5 cases every week. Isolation of influenza virus was attempted by inoculating the sample in Madin Darby Canine Kidney (MDCK) cell line. The isolates were typed by haemagglutination inhibition test and confirmed by immunoflourescence assay. RESULTS Virus isolation was positive in 30 (12.5%) of the 240 samples. Influenza A/H3N2/Panama/ 2000/99 was the predominant serotype isolated accounting for 24 (80%) of the 30 isolates. Influenza B/Sichuan/379/99 was isolated in 4 (13.33%) and a combination of Influenza A/H3N2 and B/Sichuan in 2 (6.6%) of the isolates. INTERPRETATION & CONCLUSION Isolation of influenza A and B viruses indicated a significant activity of these viruses in Chennai. Peak activity was observed during and after the first spell of rain. The predominance of A/H3N2/ Panama is an indication that the Indian scenario is similar to the global picture of influenza activity.