Abstract
BackgroundThe Influenza A pandemic H1N1 2009 (H1N1pdm) virus appeared in India in May 2009 and thereafter outbreaks with considerable morbidity and mortality have been reported from many parts of the country. Continuous monitoring of the genetic makeup of the virus is essential to understand its evolution within the country in relation to global diversification and to track the mutations that may affect the behavior of the virus.MethodsH1N1pdm viruses were isolated from both recovered and fatal cases representing major cities and sequenced. Phylogenetic analyses of six concatenated whole genomes and the hemagglutinin (HA) gene of seven more isolates from May-September 2009 was performed with reference to 685 whole genomes of global isolates available as of November 24, 2009. Molecular characterization of all the 8 segments was carried out for known pathogenic markers.ResultsThe first isolate of May 2009 belonged to clade 5. Although clade 7 was the dominant H1N1pdm lineage in India, both clades 6 and 7 were found to be co-circulating. The neuraminidase of all the Indian isolates possessed H275, the marker for sensitivity to the neuraminidase inhibitor Oseltamivir. Some of the mutations in HA are at or in the vicinity of antigenic sites and may therefore be of possible antigenic significance. Among these a D222G mutation in the HA receptor binding domain was found in two of the eight Indian isolates obtained from fatal cases.ConclusionsThe majority of the 13 Indian isolates grouped in the globally most widely circulating H1N1pdm clade 7. Further, correlations of the mutations specific to clade 7 Indian isolates to viral fitness and adaptability in the country remains to be understood. The D222G mutation in HA from isolates of fatal cases needs to be studied for pathogenicity.
Highlights
The first influenza pandemic of the 21st century was declared with the emergence of a novel Influenza A (H1N1) strain in Mexico and the USA in April 2009 [1]
The D222G mutation in HA from isolates of fatal cases needs to be studied for pathogenicity
The genetic analysis of the novel H1N1 virus isolated from a patient in California revealed that it was a recent reassortant of gene segments from both the North American and Eurasian swine lineages [7]
Summary
The first influenza pandemic of the 21st century was declared with the emergence of a novel Influenza A (H1N1) strain in Mexico and the USA in April 2009 [1]. As of December 6, 2009, the total number of confirmed cases in India was 19,632 with 621 deaths [4] Several reports describe both the emergence and the pandemic potential of the virus in the perspective of prior pandemic influenza viruses of 1918 (H1N1), 1957 (H2N2) and 1968 (H3N2) [5,6] by comparison of the available genetic sequence data. Other reports comparing the HA gene sequence with those of the earlier influenza pandemics have shown that human-specific markers supporting efficient transmissibility of these viruses in human are present in the H1N1pdm virus [9,10]. The Influenza A pandemic H1N1 2009 (H1N1pdm) virus appeared in India in May 2009 and thereafter outbreaks with considerable morbidity and mortality have been reported from many parts of the country. Continuous monitoring of the genetic makeup of the virus is essential to understand its evolution within the country in relation to global diversification and to track the mutations that may affect the behavior of the virus
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