Pandemic
From RationalWiki
A pandemic is when a dangerous disease breaks out across the world. This used to be impossible, but due to the increase in travel technology, an outbreak in one part of the world can now quickly spread to a major city and from there to the rest of the world.
Notable pandemics include the 1918 influenza pandemic and the ongoing AIDS pandemic. A recent (if less fatal) pandemic was SARS, which started in China and made its way to Toronto, Canada.
