Hsu further noted that compared to the H5N1 strain of the avian flu virus -- commonly known as bird flu -- the current H1N1 swine flu strain is still a relative lightweight. Since 2003, he said, bird flu has garnered a 60 percent case fatality rate, and it never attained pandemic status. Meanwhile, the current swine flu strain still has fewer than 1,000 reported cases and only about 60 fatalities to its name.
"If not [a pandemic] then, why now?" he asked.
But if more cases did arise, Schaffner said that a vaccine for the illness would not be available for months.
"It would be an Olympic sprint for vaccine manufacturers, starting today" to have a usable vaccine ready even by October, he said.
"If this is a virus that is sufficiently new -- and that has not been entirely determined yet -- we may need two doses of the vaccine to get protection," Schaffner said. "That, of course, would put additional strain on the vaccine production and delivery services."
Huma Khan and Michelle Schlief contributed to this report.