Diseases like dysentery, cholera, typhoid etc., are more common in over crowded human settlements. Why?

Explanation

Diseases like dysentery, cholera, typhoid etc., are more common in overcrowded human settlements with poor hygiene conditions.
Due to heaps of garbage, human excreta and animal excreta in open.
because these are infectious diseases that can transmitted from one person to another.
Chances of spread of diseases like cholera, typhoid, TB increases.
In overcrowded settlements there is more chances of transmission of disease from one person to other.