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

[Metroyeti]

Nr good info on fleas. Problem with fleas is the eggs. They can lay dormant for years,heat source(food) egg hatches in 7seconds as and the fleas on you. So stock up on tea tree oil,soap and shampoo. Lavanders also another natural repelent. Might be worth buying flea bombs if you have to bug out, new buildings could be infested, light the bomb and smoke em out.