The swine flu spam is being sent from all over the world from a network of compromised computers, with the majority coming from Brazil, the United States and Germany.
Spammers are using the virus to try to sell bogus pharmaceuticals or infect computers with malicious software.
Internet users were warned not to click on links embedded in the emails and to try to avoid opening the mail in the first place.
McAfee's director of security research, Dave Marcus, said: "Malware writers, spammers and scammers are low lives. They will use any high impact news story to push their wares."