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Going deep into the evolutionary history of H1N1 Influenza virus A, scientists have discovered that reassortment of Influenza virus happens frequently. Specifically, the scientists have found that the severe influenza epidemics that occurred in 1947 and then again in 1951 were caused by genetic reassortment events in which two human influenza influenza viruses of the same H1NI strain exchanged genetic materials, producing a new hybrid virus in both cases.
A team of researchers from Pennsylvania State University jointly with National Institute of Health (NIH) studied the evolutionary history of influenza viruses between 1918 to 2005. Their study focused on viruses that cause seasonal epidemic in humans, with an emphasizes on those that were associated with high mortality. The revolutionary research was published in the open access journal PLoS Pathogens.
The paper defines genetic reassortment as a process wherein genetic material mixes from two similar viruses that are infecting the same cell. Influenza virus A is a species of virus that causes influenza in birds, humans, pigs, and horses. The deadly Influenza virus A has often given rise to human influenza pandemics.
So far scientists were in dark as to why such deadly influenza epidemics occur periodically such as those witnessed in 1947 and 1951, when illness and mortality rates rises to unusually high levels. According to normal model of human influenza virus evolution, major pandemics, the largest of which occurred in 1918, are caused by genetic reassortment between human and avian influenza viruses. However, the seasonal influenza epidemics which occur each winter in the United States do not arise from genetic reassortment.
By putting in their hybrid influenza virus theory scientists have suggested that the evolution of seasonal influenza is more complex than was previously believed. The research implies that within a single population, multiple forms of the same strain co-circulate and re-assort thus rapidly generating genetically novel viruses that are capable of igniting major epidemics.
The authors believe that the research will prove beneficial in designing influenza vaccines. The study suggests that vaccine design can be helped if intensive surveillance can capture the full extent of influenza genetic diversity that co-circulates at a given time.
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