That echoes what Anne Schuchat, MD, the CDC's acting director for science and public health, said yesterday.
"I believe that virtually all the U.S. has this virus circulating. It does not mean everyone is infected, but within communities, it has arrived," Schuchat said at Sunday's news conference. "This virus has arrived in communities."
The CDC's official count is 286 confirmed cases in 36 states -- but Besser said there are 700 probable cases in 44 states, 99% of which will be confirmed. From now on, Besser said, the CDC will simply report probable cases, and focus more on slowing the spread of disease rather than on keeping up with what happened the day before.
The H1N1 swine flu remains a relatively mild illness for most people who come down with it. That's an encouraging sign, Besser said. Also encouraging is that the H1N1 swine flu epidemic in Mexico appears to be slowing down -- today, in fact, the Mexican government lowered its alert level to end its five-day closure of non-essential businesses.
And so far, the virus has not changed, making eventual vaccine success more likely -- if officials decide to go forward with a vaccine. Besser said that although vaccine preparation is moving full speed ahead, there's still time to decide whether to make an H1N1 swine flu vaccine, and whether the current strain will be the best to vaccinate against.
Does this mean the new flu is overhyped?
In one sense, it is. The new flu isn't as serious as the seasonal flu, which infects 30 million Americans every year and causes some 36,000 deaths.
But because it's a new flu virus, nobody knows what to expect. Nobody knows whether the H1N1 swine flu can keep smoldering throughout the spring and summer months -- or what will happen if it hits hard when flu season starts back up in the fall and winter.
"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.