How many illnesses/diseases/viruses could a fly have (contagious or not)?

And how many of these could it pass on the humans?

Question for an essay.

How many illnesses/diseases/viruses could a fly have (contagious or not)?symantic

There are hundreds but not from the fly itself. They feed on lots of really horrible things and pick up bacteria from feces, putrefied flesh etc. Interesting side note though: During wars in tropical climates doctors noticed that some wounded soldiers in the field had noticeably less gangrene. The reason was that flies were laying eggs (maggots) in the wounds. The maggots ate the putrefied flesh reducing bacterial infection then flew off.