This one is a computer virus.
It's actually a phishing e-mail, designed to convince you to put your personal information on a Web page created by a crook so they can steal from you.
Your first clue here may be the address the e-mail purports to be from, cdcmails.gov. According to the .gov whois, this is not a registered domain.
What frightens the CDC folks most about this is that it claims as its topic a real program, the state vaccination programs for H1N1. Trouble is, you don't have to register for those programs.
Victims are directed to a "personal profile" page run by the scammers.
The CDC has put out an alert on the hoax, on a continuing blog called hoaxes_rumors.
It might be fun if some researchers compared the spread of this virus to the spread of the real H1N1 strain.