Centers for Disease Control
The Centers for Disease Control and Prevention (CDC) is a branch of the United States government tasked with keeping us healthy by monitoring icky things like microbes, viruses, bug bites, and anything else that poses a threat to living healthily. Originally, it focused only as a resource for disseminating information on infectious diseases, but has since branched out to help provide information on things ranging from heart disease to obesity.
Unlike FEMA, the CDC has the authority to intern large numbers of Americans in the event of a sufficiently serious disease outbreak. Cranks don't seem to have noticed this, however. (Except InfoWars, of course.)