Originally Posted by
PeterL
It has been my opinion for years that it would be by a freshly mutated virus or bacterium. It could be either a natural mutation or something done by human intervention. A disease for which human have no natural immunity that has a high mortality rate, short incubation period, is spread by aerosols, and is fast acting (course of the disease less than a week) could greatly reduce the population in a rather short time. For example, untreated pneumonic plague has a mortality rate that approaches 100%, and it kills in as little as twenty-four hours, but some people have a natural immunity to it. The second group that would be effected by it would be in the medical profession, so there wouldn't be people to work on a cure.