Whenever your survival is in play, don’t immediately look for causes and effects. The main identifiable reason for our survival of such diseases might simply be inaccessible to us: we are here since, Casanova-style, the “rosy” scenario played out, and if it seems too hard to understand it is because we are too brainwashed by notions of causality and we think that it is smarter to say because than to accept randomness. Taleb, Nassim. The Black Swan (p. 120). Penguin Books Ltd. Kindle Edition.
Make a step back
Also, causality gives us the illusion of control.