Molecular and epidemiological analysis of pandemic and post-pandemic influenza A(H1N1)pdm09 virus from central India.

Influenza A(H1N1)pdm09 virus pandemic struck India in 2009 and continues to cause outbreaks in its post-pandemic phase. Diminutive information is available about influenza A(H1N1)pdm09 from central India. This observational study presents epidemiological and molecular findings for the period of 6 years. Throat swab samples referred from districts of Madhya Pradesh were subjected to diagnosis of influenza A(H1N1)pdm09 following WHO guidelines. Clinical and epidemiological data were recorded and analyzed. Hemagglutinin (HA) gene sequencing and phylogenetic analysis were performed. The H275Y mutation responsible for antiviral resistance was tested using allelic real-time RT-PCR. Out of 7365 tested samples, 2406 (32.7%) were positive for influenza A(H1N1)pdm09, of which 363 (15.08%) succumbed to infection. Significant trends were observed in positivity (χ2  = 50.8; P < 0.001) and mortality (χ2  = 24.4; P < 0.001) with increasing age. Mutations having clinical and epidemiological importance were detected. Phylogenetic analysis of HA gene sequences revealed that clade 7, 6A, and 6B viruses were in circulation. Oseltamivir resistance was detected in three fatal cases. Influenza A(H1N1)pdm09 viruses having genetic diversity were detected from central India and continues to be a concern for public health. This study highlights the need of year-round monitoring by establishment of strong molecular and clinical surveillance program.