Aside from nuclear meltdowns occurring worldwide post TEOTWAWKI, deadly diseases and viruses spreading worldwide is arguably the next biggest danger to humanity. History is wrought with cases of deadly pandemics killing off in some cases up to 50% of a regions population. Governments are currently doing a great job at quarantining outbreaks but every so often a virus becomes pandemic and uncontrollable. If for whatever reason the system responsible for vaccinations/quarantining and viral research falls apart, the population worldwide (especially in large cities) would quickly succumb to deadly pandemics. Fortunately, there are things you can do right now to prepare for such a crisis.