Question: Do you think that there will be ever a SUPER-MEGA killer disease that will wipe out the Earth's entire population to extinction?

Ee Lyn Lim answered on 21 Jun 2013:

Try thinking about this from the perspective of the disease! Say it’s a bacteria, or a virus. It’s so super-mega powerful that it’s killed every thing else in the world, and now it’s the only thing left alive. What now? Will it eat itself? Sooner or later it, too, will die and disappear. That’s not something it wants to happen!

The best, most successful infectious organisms never kill their hosts. When the host dies, the bacteria and viruses lose a safe comfy home, a source of food, and a place to reproduce. Now why would you do that? The best thing is to live happily together with the host, so that there are more and more people for you to infect. Maybe cause a little coughing or sneezing, or maybe some diarrhoea, so that you can get out of the host body and and infect other people, but never actually kill the host! Some scientists think that the bacteria and viruses which cause serious fatal diseases have actually just been introduced to humans relatively recently, so they haven’t quite found the right balance yet. If anything, pathogens will want to evolve to be LESS lethal, rather than more!