In Austin, so many parents are rushing their children to the Dell Children's Medical Center of Central Texas with swine flu symptoms that the hospital had to set up tents in the parking lot to cope with the onslaught.

In Memphis, Tenn., the Le Bonheur Children's Medical Center emergency room got so crowded with feverish, miserable youngsters that it had to do the same thing.

And in Manning, S.C., a private school where an 11-year-old girl died shut down after the number of students out sick with similar symptoms reached nearly a third of the student body.

After months of warnings and frantic preparations, the second wave of the swine flu pandemic is starting to be felt around the country. Doctors, clinics, hospitals and schools are reporting rapidly increasing numbers of patients with flu symptoms.

"H1N1 is spreading widely throughout the U.S.," Thomas Frieden, director of the federal Centers for Disease Control and Prevention in Atlanta, said at a briefing Friday. At least 26 states are now reporting widespread flu activity, up from 21 a week earlier, the CDC reported.

While so far most cases are mild, and the health care system is handling the load, officials say the number of people seeking treatment for flu is unprecedented for this time of year. Even though some parts of the Southeast that started seeing a surge of cases first now seem to be showing a decline in cases, that could be a temporary reprieve, Frieden said. And other parts of the country are likely just starting to feel the second wave.

"We can't predict what's going to happen in the future," Frieden said. "Influenza is perhaps the most unpredictable of all infectious diseases."

Swine flu, also known as H1N1, tends to strike more younger people than the usual seasonal flu. At least 49 children have died from complications caused by the virus so far in the U.S.