We spent a couple weeks roaming India several months ago. There appeared to be an absence of understanding and appreciation of both personal and public hygiene...everywhere. We were amazed that everyone wasn’t sick or dead.
Well, yes and no. The specialty hospitals that cater to medical tourism are state of the art in medical technology and pathogen control. The upper classes, especially those with a family member who has studied abroad, also tend to be western-like in that regard.
While living in India, my wife came into contact with many diseases unknown here in the states such as cholera. However, she personally is extremely circumspect about sanitation and cleanliness. But living in a slum, you're going to come into contact with that stuff.
Your comment: "We were amazed that everyone wasn’t sick or dead" shows that most of us are tougher than western ideas make us think we are. A properly functioning immune system can fend off a lot of day-to-day infectious threats. But not Ebola.