Pandemic H1N1 was first observed in the year 1918 in Spain, where it caused millions of deaths. Later, several outbreaks of influenza virus were reported in 1968, 1998, 2009 and so on. Recently, from 13 May 2012 to 26 May 2012, 19,710 specimens were tested for influenza virus. Out of those specimens, 2297 were positive for influenza viruses, of which 1699 were influenza A (including 157 that were pH1N1-positive) and 598 were influenza B. Antigenic drift results in mutation of the viral genome, potentially improving its efficiency as a pathogen. A total of 90% of influenza-related deaths occur in older adult populations, indicating that viral dysregulation of the immune system becomes more severe with age, owing to immunosenescence. Influenza virus infection leads to symptoms such as fever, body pain, sore throat, loss of appetite, headache, cough, aching muscles and joints, weakness, fatigue, pneumatoceles, mediastinal emphysema and secondary renal failure leading to fatality in extreme cases.
Future Virology. 2012;7(10):947-950. © 2012 Future Medicine Ltd.