Influenza A H1N1 virus in Indian pigs & its genetic relatedness with pandemic human influenza A 2009 H1N1.

Background & objectives: With the emergence of a new reassortant influenza A H1N1 virus that caused the 2009 pandemic it was felt necessary that pigs should be closely monitored for early detection of any influenza virus infection. Therefore, we investigated disease outbreaks with clinical history suggestive for swine influenza reported to our laboratory by owners of affected pig farms in Uttar Pradesh. Methods: Detection of swine influenza A virus (SIV) was attempted by isolation in embryonated chicken eggs. Presence of virus was detected by haemagglutination (HA) test and RT-PCR for amplification of different gene segments, cloning and sequencing. BLAST analysis of sequence data, phylogenetic analysis and mutation analysis based on HA, NA and matrix genes was done. Results: SIV could be isolated from one farm and all eight gene segments amplified by RT-PCR. BLAST analysis of partial nucleotide sequences and phylogenetic analysis using nucleotide sequence of HA (601 nt), NA (671 nt) and M (1031 nt) genes indicated close genetic relationship of the Indian swine isolate (A/Sw/UP-India-IVRI01/2009) with human pandemic 2009 (H1N1). The HA gene showed close relationship with the viruses of “North American Swine” lineage, whereas the NA and M genes clustered with the viruses of “Eurasian Swine” lineage, indicating a novel HA-NA reassortant. The remaining of 5 genes (NP, PA, PB1, PB2 and NS) belonged to “North American Swine” lineage. Interpretation & conclusions: This is perhaps the first report describing swine influenza among Indian pigs caused by an influenza A H1N1 virus sharing close homology with the human pandemic (H1N1) 2009 virus. Further reassortment with circulating influenza viruses must be closely monitored.

Novel swine-origin H1N1 influenza / 소아과

Since its identification in April 2009, a swine-origin H1N1 influenza A virus (S-OIV) which is a reassortment of gene segments from both North American triple-reassortant and Eurasian swine influenza has been widely spread among humans in unexpected rapidity. To date, each gene segment of the 2009 influenza A (H1N1) outbreak viruses have shown high (99.9%) neucleotide sequence identity. As of July 6, 94,512 people have been infected in 122 countries, of whom 429 have died with an overall case-fatality rate of <0.5%. Most confirmed cases of S-OIV infection have been characterized by self-limited, uncomplicated febrile respiratory illness and 38% of cases have also included vomiting or diarrhea. Standard plus droplet precautions should be adhered to at all times. Tests on S-OIV have indicated that current new H1N1 viruses are sensitive to neuraminidase inhibitors (oseltamivir). However, current less virulent S-OIV may evolve into a pathogenic strain or acquire antiviral resistance, potentially with more severe clinical consequences. Efforts to control these outbreaks would be based on our understanding of novel S-OIV and previous influenza pandemics.