Overall, "examination of past pandemics reveals a great diversity of severity," Morens and Taubenberger said, adding that "some newer evidence [is] casting doubt on original herald wave theories."
One infectious-disease expert called the new analysis "absolutely correct."
Looking back at 20th century flu pandemics, "secondary waves have pretty much been either the same or even of less epidemiologic significance than the first wave," said Dr. Pascal James Imperato, dean of the school of public health at SUNY Downstate Medical Center in New York City.
And as for the current H1N1 swine flu pandemic, the NIAID experts believe that the relatively poor transmissibility of the virus, the fact that many people have some pre-existing immunity, and its arrival in the Northern Hemisphere in late spring "all give reason to hope for a more indolent pandemic course and fewer deaths than in many past pandemics."
Imperato concurred with that assessment. Swine flu is "still circulating," he said, "and that means that a lot of people have developed protection against it, plus we have the advantage that it's a descendant of other H1N1 viruses that were in circulation in the late '70s through the '80s, so older people have solid protection."
"It's hard to conceive that if the H1N1 should reappear in the fall in the Northern Hemisphere that we would have a more severe epidemic," he said.
This should come as good news as the United States gears up for the coming fall flu season. This week, volunteers began lining up at centers nationwide as the first swine flu vaccine trials began.
"The best way to prevent the spread of the flu is vaccination," U.S. Department of Health and Human Services Secretary Kathleen Sebelius told reporters on Friday, "and our scientists are
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