From the ground breaking and life saving to the wacky and implausible, Dr Karl Kruszelnicki reveals some of the best moments in science.
http://www.abc.net.au/radionational/programs/greatmomentsinscience/
Sydney smallpox epidemic
We're now quite familiar with terms like 'herd immunity' and 'epidemic', and that when separate groups of people—with separate germs—meet for the very first time, things can turn out badly. If you have never been exposed to a specific germ you won't be primed for protection against it.