click green flag to start. Viruses and bacteria can spread just by someone breathing on you or if you drink water from a contaminated, and you can die from some viruses or bacteria in only 24 hours from when you get it. Not every one will die in an outbreak but depending on the severity of the disease sometimes more than half of the people infected can die.
https://sites.google.com/lcps.org/outbreak/home/hitting-close-to-home-meningitis