If influenza was only contagious after symptoms appear it would have died out thousands of years ago.
Somewhere between tool using and cave painting, homo habilus would have figured out to kill the guy with the runny nose.
Take your stinking paws off my popcorn you damn dirty ape.
runny 柔らかすぎる、粘液を分泌する
paw （爪のある動物の）足、（人の）手、おとうさん