How long post SHTF before a city is safe to re enter?

[NorthernRaider]

BDG is forgetting that there is far more to worry about than just bubonic plague, Theres Lepto spirosis, Choilera, Typhus, E -Coli, Botulism etc etc that will thrive for years among the dead and dying a dying city is just one giant petrie dish of bacteria and germs all looking for someone to infest, not to mention the imported untreatable TB, VHF etc that is still thiving in our immigrant community 99.9% of whom live in cities.