I learned all that when I was nursing, years ago.Flies spit on everything they touch to moisten what they are about to eat. So maybe theyhave been on a dung heap before they land on your food and spit on that.
So nothing new there. What have these new scientists been learning?

I don't really have a problem with flies where I live now, but my last place always seemed to be plagued with them - but I always put that down to living near a farm.

Horrible pesky flies don't last a minute in my house. It is mainly the summer months that we are bothered by them when we like the windows open. When I am busy in the kitchen I keep the back door open wide, and if they get in, their only escape is to fly straight out again, it is just a small kitchen, so can't get very far. I keep the main doors shut so they can't get through. I hate squatting them as it leaves a mess for me to clear up and don't really want to touch them. So I just let them fly straight out again. Same with the patio doors. they escape out of there. They don't last a minute with me if the do get trapped in by finding their way in via a window.

I've always taken it as said that files were mini flying disease bags anyway - that's why commercial kitchens have to have those UV fly traps.

Can't say I've ever been keen on them, but that article is a bit of a revelation.

An 'ew' article: http://www.bbc.co.uk/news/science-environment-42113217