A pilot study of seroprevalence of influenza virus type A in Vellore, south India.

ABSTRACT

BACKGROUND & OBJECTIVES: Influenza virus type A is active in many regions of the world. However, information from many parts of India is sparse. Hence we carried out a serological study on the prevalence of antibodies to influenza virus type A in Vellore, south India. METHODS: Antibodies to influenza virus type A (H1N1 and H3N2) were detected using a haemagglutination inhibition (HI) test. A total of 186 individuals comprising healthy blood donors and laboratory workers were tested. RESULTS: The titres ranged from < 20-2580, with a high geometric mean titre (GMT) of 200 for H3N2 and < 20-1280 with a GMT of 74 for H1N1 serotype of influenza virus type A. Among the 186 serum samples tested, 175 (94.04%) were positive for H1N1 and 185 (99.5%) for H3N2 with a titre > 20. INTERPRETATION & CONCLUSION: The prevalence of elevated level of antibodies in the individuals indicates a high exposure to the influenza A virus in our population with a seropositive status in 99.5 per cent of the individuals tested. Virus surveillance needs to be instituted in different parts of the country to monitor the activity of these viruses.