The public health implications of the pandemic therefore remain in doubt even as we now grapple with the feared emergence of a pandemic caused by H5N1 or other virus.
However, new information about the 1918 virus is emerging, for example, sequencing of the entire genome from archival autopsy tissues.
But there are no known precursor viruses to the 1918 strain, so the computational results can only infer the time of interspecies transmission, based on known patterns of genetic evolution.
Such studies have only become possible in the past few years, with the advancement of computational techniques that can incorporate known rates of various species’ evolution–techniques that are proving to be quite accurate when tested against known relationships.
But the results are still, as Smith notes, “all just inference,” working backward from known relationships and based on estimated dates.
The "Spanish" influenza pandemic of 1918–1919, which caused ≈50 million deaths worldwide, remains an ominous warning to public health.
Many questions about its origins, its unusual epidemiologic features, and the basis of its pathogenicity remain unanswered.
All influenza A pandemics since that time, and indeed almost all cases of influenza A worldwide (excepting human infections from avian viruses such as H5N1 and H7N7), have been caused by descendants of the 1918 virus, including "drifted" H1N1 viruses and reassorted H2N2 and H3N2 viruses.
The latter are composed of key genes from the 1918 virus, updated by subsequently incorporated avian influenza genes that code for novel surface proteins, making the 1918 virus indeed the "mother" of all pandemics.
, suggests that all three influenza pandemics–1918, 1957, and 1968–were the result of stepwise genetic integrations of both avian and mammalian genes over a number of years, ultimately creating the more virulent virus strains.
And although the research was done before the emergence of the current H1N1 “swine flu” strain, the scientists’ conclusions are relevant, showing that the current virus follows the same historical pattern.
The study's findings suggest people are made critically ill, or even killed, by their own immune response.
A hallmark of pandemic flu throughout history, including the 2009 H1N1 pandemic, has been its ability to make healthy young and middle-aged adults seriously ill and even kill this population in disproportionate numbers. 5 in Nature Medicine, Vanderbilt University Medical Center researchers provide a possible explanation for this alarming phenomenon of pandemic flu.
Martin was among the first wave of critically ill middle Tennesseans, hit hard by the H1N1 flu pandemic in late 2009.