a common cause of serious illness in a disaster is waterborne bugs. how about prevention, diagnosis and treatment? I don't think a lot of people get, that splashing around in their favorite swimming hole once a summer is very different from drinking that same water on a daily basis.
Or vector borne illness. people unexpectedly forced outdoors during a disaster will be exposed in ways their daily experience won't prepare them for.
F-O illness - how many urbanites today understand hygiene outdoors?
in most disasters - dealing with the environment after the disaster is as dangerous as the cause of the disaster.