So far, young people have been the most likely victims of swine flu, but that could change, says Rear Admiral Anne Schuchat, the interim deputy director of the Centers for Disease Control and Prevention's Science and Public Health Program.
As she tells All Things Considered's Melissa Block, children and young people are much more social and that helps promote the flu, which spreads mainly through coughs and sneezes. But as the flu enters adult social networks, it could take off and spread like the regular seasonal flu does.
Schuchat says that the new H1N1 flu virus is "at least as virulent as the regular seasonal flu," but it's still not known whether it could be more lethal. CDC estimates there are about 100,000 cases of swine flu in the U.S. right now.
Whether we're in for an unusual "summer flu" season isn't clear. It could stop spreading soon, or it might persist for weeks in North America, she says.
The CDC will be watching to see if this H1N1 strain takes on new characteristics as it moves into the Southern Hemipshere and through more human populations in the coming months. That will determine whether the world will face a deadly pandemic on the order of 1968, 1957 or even the great 1918 pandemic. The jury's still out on what'll happen.
For more of Block's interview with Rear Adm. Schuchat, listen to today's ATC on your local NPR station. (Find it here.)
And a shout out to Mark Memmott of NPR's newest news blog, "The Two-Way" for his help on this.