Dating the emergence of pandemic influenza viruses

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Mean TMRCA estimates also suggest that the avian-derived genes of the H2N2 and H3N2 pandemic strains may have been introduced to humans on multiple occasions over a number of years. We also show that seasonal and classic swine H1N1 viruses were not derived directly from BM/1918; rather, their precursors co-circulated during the pandemic. These pandemics were initiated by the introduction and successful adaptation of a novel hemagglutinin subtype to humans from an animal source, resulting in antigenic shift. In the 20th century, 3 influenza viruses caused major pandemics: the 1918 H1N1 virus, the 1957 H2N2 virus, and the 1968 H3N2 virus.Here we estimated the evolutionary history and inferred date of introduction to humans of each of the genes for all 20th century pandemic influenza strains. Estimates for BM/1918 virus TMRCAs (node 2) ranged from 1903 (BCI 1867–1918) for the PB2 gene to 1916 (BCI 1910–1918) for the HA gene ().

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dating the emergence of pandemic influenza viruses-64

We therefore investigated evolutionary mechanisms of pandemic emergence by conducting comparative genetic analyses of all available viruses associated with the emergence of the 1918, 1957, and 1968 pandemics.

These pandemics were initiated by the introduction and successful adaptation of a novel hemagglutinin subtype to humans from an animal source, resulting in antigenic shift (4, 5).

In the 20th century, 3 influenza viruses caused major pandemics: the 1918 H1N1 virus, the 1957 H2N2 virus (H2N2/1957), and the 1968 H3N2 virus (H3N2/1968) (2, 3).

Here we estimated the evolutionary history and inferred date of introduction to humans of each of the genes for all 20th century pandemic influenza strains.

Despite global concern regarding a new pandemic influenza, the emergence pathway of pandemic strains remains unknown.

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