H1N1 Swine Flu: No State Is Immune
CDC: 'Virtually All the U.S. Has This Virus Circulating'
"I am particularly concerned about what will happen in the fall," Schuchat says.
And if the new flu started to spread in the Southern Hemisphere -- where it's now autumn -- it could pick up speed just as that flu season starts up.
"We are watching what happens in the Southern Hemisphere," Besser said. "We will work closely with the international community to see what happens with this virus over their winter, whether the virus is changing, whether it becomes more severe, and what measures we will take in the fall."
So far, though, most U.S. H1N1 flu cases have been relatively mild. It's flu, of course, so the CDC fully expects more hospitalizations and more deaths. It's possible the new flu could mutate to become even milder. On the other hand, it's also possible it could become much more severe. That is the specter that keeps public health workers awake at night -- and working every weekend.
"It is important that the encouraging signs we've seen don't mean people will let down their guard," Besser said. "Handwashing, covering your sneeze with your sleeve and not your hand, staying home when sick -- these things are really important any time, but especially now, when we have a virus we are still learning about spreading in our communities."
Like seasonal flu, H1N1 swine flu can move fast. In New York City, the new flu spread quickly through a high school, infecting one in three students.
"What we can learn from the New York City survey is this virus spread pretty easily in those high school students," Schuchat said.
Currently, the CDC recommends that schools shut down for two weeks if a student comes down with a confirmed or even suspected case of the new flu.
Besser hinted that the CDC might move toward the model being used in Seattle, where parents are asked to check their children carefully for signs of illness -- and, if they appear ill, to keep them home for at least seven days, even if they feel better.
Teachers would be told to monitor their classes for children who appear ill. Sick children would immediately be sent home. And, students would receive repeated instruction on handwashing and sneezing/coughing into their sleeves instead of their hands.