Influenza A virus movement is tracked

STATE COLLEGE, Pa., Sept. 20 (UPI) -- A U.S. study has found the influenza A virus isn't dormant during summer but migrates globally and mixes with other viral strains.

Pennsylvania State University researchers said their finding resolves a key debate on what the virus does during summer when it isn't infecting people.

"Nobody really knows why flu is a winter disease in the temperate regions and more continuous in the tropics," said Penn State biology Professor Edward Holmes.

Holmes said the key question is whether the virus settles into a dormant state or whether it migrates to viral reservoirs in the tropics, from where it is later reintroduced.

To test the migration theory, Holmes, graduate student Martha Nelson and National Institutes of Health colleagues Lone Simonsen, Cecile Viboud and Mark Miller analyzed the influenza A virus genomes of 900 virus samples from New Zealand, Australia and New York state

They discovered the genomes of 52 viruses from New York are closely related to viruses that circulate during the winter (April to October) in New Zealand and Australia. That, they said, suggests seasonal viral traffic across the equator contributes to new epidemics in both hemispheres.

The findings appear in the current issue of PLoS Pathogens.

Copyright 2007 by United Press International

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