How influenza spreads each year

 Not found on Wikipedia (thought the article gets real close)

The main article used  as a source for the Wikipedia article doesn't mention it.  Long answer short, it's ducks.  Pooping in water.  The virus mutates in ducks each year, when they migrate south, they infect bodies of water with flu laden poop.  It spreads through domestic ducks, chickens, maybe turkeys, pigs and people, through poop.

The long answer is much longer.

To be continued ...