Felix, I tramped about the Giza Plateau in a stonkingly hot April while PG, had a MC 1 week later. Could have happened anyway, but I'll never know.
I lived in Egypt for 3 years, never got food poisoning. Mind you, never went out, had to cook my own food....
My mum did come down with Pneumonia 15 days after going back to the UK, 6 days in ICU, not sure if that could have been something she picked up over there.
AFAIK, the only place to go at the moment is the Red Sea. But it's hotter than hell there for now. WRT security, there it's situation normal. Cairo, Giza and Alex are not as safe as they were, there is no effective policing system. Care also is advised in Luxor, although I do know that there are holiday excursions going there, so it must be safer than other large cities.
Health and Safety are alien concepts in Egypt. Cleanliness too is not a natural given. Mostly life there is dusty, filthy, litter strewn and a broken mess. I'm sure tourist resorts are better, but again germs are not easily seen, if cleaners can get away with skipping something, they will.
I will never, ever go back.