Prevalence and epidemiology of outbreaks of influenza A(H1N1)pdm09 virus in Gujarat from August 2009 to March 2016 with special reference to 2015 resurgence

Purpose: Influenza is a widespread viral infection and a major cause of morbidity and mortality worldwide. The present study was performed to investigate the Influenza A H1N1 2009 pandemic (influenza A(H1N1)pdm09) virus outbreaks, its pattern and its clino-epidemiological correlation in and around the region of Gujarat, during the period of August 2009 to March 2016 with special reference to outbreak of 2015. Materials and Method: This is a retrospective study. A total of 17206 patients attending various hospitals in Gujarat were included from August 2009 to March 2016. Nasal swabs, nasopharyngeal swabs, or throat swabs were collected and tested by real time Reverse Transcriptase PCR (rRTPCR) for presence of influenza A(H1N1)pdm09 virus. Results: Out of 17206 samples, 6078 clinical samples were positive for swine flu and 2605 were positive for seasonal Influenza A flu. Over all people in the age group between 30 years to 60 years were highest affected and females were affected more than males. Case fatality rate of the patients admitted in our hospital in 2015 outbreak was 23.07% with highest mortality in pregnant women. Conclusions: Influenza A(H1N1)pdm09 is still active six years after 2009 pandemic and unable to replace seasonal influenza A virus unlike previous pandemic strains. Middle age patients and pregnant women were highly affected with high mortality in pregnant women. Keywords: Influenza A(H1N1)pdm09, Seasonal influenza A, Outbreaks, rRT-PCR