New guidelines for evaluating flu pandemics

The Centers for Disease Control and Prevention unveiled a new pandemic severity index today. It categorizes how virulent a flu strain may be.

A Category 1 pandemic is the least severe. That would require sick patients to stay home.

A Category 5 is considered highly deadly and would require states to close schools and cancel large gatherings.

A new public service announcement is also part of the effort. It encourages Americans to learn about pandemics and what they might need to do if one strikes.