Max, at this point I doubt you are going to hear much radio traffic from either the CDC or the HHS. Although both agencies do have allocated frequencies, the only ones for the CDC I have ever confirmed were used for facility maintenance & security at the CDC HQ in Atlanta. I suspect most current health emergency communications are taking place via cell phone, email, etc..
As for the HHS, I covered that agency in the March 2008 Fed Files in Monitoring Times. I just posted the frequencies from that article on the Fed Files blog. You are welcome to give them a try and see what's up. But I'm pretty sure that if it gets to the point of HHS out using radios for the Swine Flu, look for DMAT, FEMA, the National Guard and all your local government agencies to be busy too...
- Chris