If a huge infectious disease hit, what would the government do for the masses?

Good question!: I guess that would depend on which government we have at the time: one that believes in the importance of maintaining a taxpayer-funded public health infrastructure, or one that believes that government is "the problem" and it's every man for himself. I highly recommend the film "contagion" for an example of why public health is important.

Preventive Medicine: The cdc and nhs maintain surveillance for such illnesses along with help from other international services like the who. They develop vaccines, stockpile medications to combat these processes and keep the public informed of things they can do to prevent becoming infected or spreading it.