Read about the 1918 flu epidemic. Eventually it went everywhere. Even isolated fijian islands lost 15% of their population. Some cities who quaratined to avoid it ended up with worse outbreaks. It came in waves and seemed to mutate to a worse version then later a less harmful version. Symptoms could be mild to dramatic and rapid.
A major lesson was that truth helped. Lies and dowplaying the seriousness was a common response at national and local city level. Wartime censorship hindered the spread of useful information. These approaches created worse outbreaks through lack of preparedness and a much more fearful population.
