I guess in a tsunami, you would have no choice. But thinking about the bioterrorism or bird flu epidemic possibilities, the last thing I'd wanna do is run to a supermarket and have some 6 year old kid cough up something green on me!
The bird flu self quarantine option is another reason to have a year's food on hand ASAP.
Yup, Think about what you're doing before you do it. I bought some N95 face masks on an impulse because they claimed to remove 95% of all particles at .30 microns or larger. It wasn't until later that I did my 'homework' and found out that most viruses are .15 microns or smaller. Live and learn.