A study led by Michael Worobey at the University of Arizona in Tucson provides the most conclusive answers yet to two of the world's foremost biomedical mysteries of the past century: the origin of the 1918 pandemic flu virus and its unusual severity, which resulted in a death toll of approximately 50 million people.
Worobey's paper on the flu, to be published in the early edition of the Proceedings of the National Academy of Sciences (PNAS) on April 28, not only sheds light on the devastating 1918 pandemic, but also suggests that the types of flu viruses to which people were exposed during childhood may predict how susceptible they are to future strains, which could inform vaccination strategies and pandemic prevention and preparedness.
"Ever since the great flu pandemic of 1918, it has been a mystery where that virus came from and why it was so severe, and in particular, why it killed young adults in the prime of life," said Worobey, a professor in the UA Department of Ecology and Evolutionary Biology. "It has been a huge question what the ingredients for that calamity were, and whether we should expect the same thing to happen tomorrow, or whether there was something special about that situation."
The origin of the 1918 pandemic influenza A virus (IAV) and the reasons for its unusual severity are two of the foremost biomedical mysteries of the past century. The researchers now infer that the virus arose via reassortment between a preexisting human H1 IAV lineage and an avian virus. Phylogenetic, sero-archeological, and epidemiological evidence indicates those born earlier or later than ∼1880–1900 would have had some protection against the 1918 H1N1 virus, whereas many young adults born from ∼1880–1900 may have lacked such protection because of childhood exposure to an antigenically distinct H3N8 virus. These findings suggest that better understanding of how initial exposure shapes lifetime immunity may enhance the prediction and control of future IAV pandemics and seasonal epidemics.