Most of these questions have no solid answers -- at least not yet -- but there are some intriguing possibilities.
The death rate from the swine flu in Mexico (149 by late Monday) hovers at about 7 percent of the more than 1,900 so far thought to be infected -- a percentage that's alarmingly higher than the 1918 Spanish flu pandemic, which is thought to have killed about 2.5 percent of infected persons.
But this early in the outbreak, no one really knows the true extent of the Mexican outbreak, the experts noted, so that 7 percent figure might well be too high.
"We don't know the total number of people exposed," Topham said. "It could be many more people exposed, so we're only hearing about the ones who got really sick and died," he explained.
It's also not clear if all the deaths attributable to swine flu were actually caused by the virus.
"The strain in the U.S. seems to be the same as in Mexico, but in Mexico we've not had confirmation of all those hospitalizations or deaths," Lillibridge said. "We're comparing apples and oranges."
And to put things into perspective, even with the death toll in Mexico, the swine flu does not appear to be as dangerous as SARS (Severe Acute Respiratory Syndrome), which appeared seemingly out of nowhere in 2003.
"SARS had high human-to-human transmission, there was a high death rate and no treatment," Horovitz noted. With the swine flu outbreak, "we're not talking about anything like that," he said.
In fact, all 40 U.S. cases so far have been mild or the patients have recovered, the U.S. Centers for Disease Control and Prevention reported.
And, in absolute numbers, the death toll is still nowhere near the roughly 35,000 lives snatched each year by the regular "garden variety" seasonal flu, Horovitz pointed out. <
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