Abstract
To investigate the aetiology of the 2015 A(H1N1)pdm09 influenza outbreak in India, 1,083 nasopharyngeal swabs from suspect patients were screened for influenza A(H1N1)pdm09 in the state of Madhya Pradesh. Of 412 positive specimens, six were further characterised by phylogenetic analysis of haemagglutinin (HA) sequences revealing that they belonged to genogroup 6B. A new mutation (E164G) was observed in HA2 of two sequences. Neuraminidase genes in two of 12 isolates from fatal cases on prior oseltamivir treatment harboured the H275Y mutation.
Highlights
To investigate the aetiology of the 2015 A(H1N1)pdm09 influenza outbreak in India, 1,083 nasopharyngeal swabs from suspect patients were screened for influenza A(H1N1)pdm09 in the state of Madhya Pradesh
The RNA samples were screened by World Health Organization (WHO)–Centers for Disease Control and Prevention (CDC) approved quantitative real-time reverse transcription-polymerase chain reaction for influenza A(H1N1)pdm09 [3]
Six clinical samples testing positive for influenza A(H1N1)pdm09 by quantitative real-time reverse transcription-polymerase chain reaction (qRT-PCR) were selected based on patients’ disease severity category A (n=2; A/India/ DRDE_GWL897/2015 and A/India/DRDE GWL721/2015), B (n=2; A/India/DRDE_GWL703/2015, A/India/ DRDE_GWL989/2015), and C (n=2; A/India/DRDE GWL719/2015 and A/India/DRDE_GWL812/2015) as previously described [2], and used for direct nucleotide sequencing of the haemagglutinin (HA) gene
Summary
Emergence of influenza A(H1N1)pdm genogroup 6B and drug resistant virus, India, January to May 2015. A new mutation (E164G) was observed in HA2 of two sequences. Neuraminidase genes in two of 12 isolates from fatal cases on prior oseltamivir treatment harboured the H275Y mutation. We show that genotype 6B strains forming two sub-lineages circulated during the outbreak. Comparison of the sequences of six outbreak strains recovered in this work, to other published genotype 6B sequences, reveals a unique combination of previously-reported mutations in the haemagglutinin (HA) gene. Among strains analysed from 12 fatal cases on prior oseltamivir treatment, two harbour the H275Y mutation in the neuraminidase (NA) gene, which confers resistance to this antiviral
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