Sep 28 2016
Right now it’s flu shot season, soon to be followed by flu season itself from December to March.
Wild birds have been blamed as a source of influenza but new evidence indicates they’re not the cause of bad flu. To understand why here’s a primer on where flu comes from, how it spreads, and why flu season is in the winter.
Where does flu come from?
Other people! It spreads best — and quickly creates new strains — where people are densely crowded. Amazingly, the Spanish Flu Epidemic of 1918 spread quickly because of crowded camps and trenches in World War I. A new study this month from the University of Chicago finds that “surveillance for developing new, seasonal vaccines should be focused on areas of east, south and southeast Asia where population size and community dynamics can increase transmission of endemic strains of the flu.” Click here to read why flu does so well in that part of the world.
How does flu spread? In the air. We breathe it in. Airborne transmission actually explains …
Why is flu season in the winter?
Not too long ago we were told that it’s in the winter because migratory waterfowl pass avian flu to domestic birds during fall migration. Wrong!!
Recent studies of avian flu transmission show that it spreads in poultry factory farms (crowded conditions!) and along our poultry trade routes. It follows our poultry, not wild birds’ migratory paths.
And the timing has nothing to do with migration. Flu season is in the winter because the pathogen stays airborne longer in dry winter air. It falls to the ground in summer humidity.
So why are waterfowl off the hook?
Wild birds aren’t spreading the worst strains of avian flu because they don’t have it.
After the H5 avian influenza A virus hit U.S. poultry farms in 2014-15, officials worried that avian flu would return when waterfowl migrated south again … but it didn’t. The reason was found by researchers from St.Jude Children’s Research Hospital who “analyzed throat swabs and biological samples taken from 22,892 wild ducks and other aquatic birds collected before, during and after a 2014-15 H5 flu outbreak in poultry.”(*) None of the birds had the highly pathogenic influenza A virus.
“Bad flu is not our fault,” say the ducks.
(photo by Brian Herman)