title: A pilot study of seroprevalence of influenza virus type A in Vellore, south India.
abstract: OBJECTIVE
  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.
  
  
  CONCLUSIONS
  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.
mesh_terms: D000914:Antibodies, Viral / Q000097:blood*; D003430:Cross-Sectional Studies; D006385:Hemagglutination Inhibition Tests; D006801:Humans; D007194:India / Q000453:epidemiology; D009980:Influenza A virus / Q000276:immunology*; D007251:Influenza, Human / Q000453:epidemiology*; D010865:Pilot Projects; D016036:Seroepidemiologic Studies
chemical_list: D000914:Antibodies, Viral