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Virus evolution and human behaviour shape global patterns of flu movement

last modified May 25, 2016 09:33 AM
The global movement patterns of all four seasonal influenza viruses are illustrated in research published today in the journal Nature, providing a detailed account of country-to-country virus spread over the last decade and revealing unexpected differences in circulation patterns between viruses.

In the study, an international team of researchers led by the University of Cambridge and the Fred Hutchinson Cancer Research Center, and including all five World Health Organization (WHO) Influenza Collaborating Centres, reports surprising differences between the various types of seasonal flu virus, which they show to be due to the rate at which the different viruses evolve.

There are four types of influenza viruses that cause seasonal flu in humans: two influenza A viruses (H3N2 and H1N1) and two influenza B viruses (Yamagata and Victoria). While H3N2 viruses are the most common of the seasonal influenza viruses, H1N1 and B viruses also cause epidemics worldwide each year, hence the WHO selects representative strains of all four A and B viruses for inclusion in the seasonal influenza vaccine each year.

Importantly, all four of the viruses cause indistinguishable symptoms and evolve by similar mechanisms to escape immunity induced by prior infections and vaccinations. This ‘antigenic’ evolution is part of why people get influenza multiple times over the course of their lives. Read more..