People born before 1918, it appears, are immune. But there's concern about the very young, especially as they go to summer camp, reports CBS News medical correspondent Jennifer Ashton.
Kids have been coming to North Carolina's Blue Ridge Mountains for the Blue Star camp experience for 60 years. But this year 13-year-old Nikki Jaffe experienced something she never expected.
"I had a really bad headache. I just didn't feel good overall, and I was coughing a lot," Jaffe said.
Eleven-year-old Jessica Bachner says she'd never felt so bad.
"It felt different than having a fever," she said. "It was more."
it was, in fact, likely H1N1 or swine flu, now spreading through summer camps across America. At least 50 have reported outbreaks and the Centers for Disease Control is urging all camps to take precautions. Since the new flu is affecting people between the ages of 5 and 24 more than any other group, campers and counselors are especially vulnerable.
At Blue Star, two campers tested positive and 35 others were believed to be infected, but none of the cases were serious. They were given anti-viral medication and isolated.
"They'd come in the first day with about 101, take their Tamiflu," said Rodger Popkin, owner and director of Blue Star Camps. "By the third day they wanted to go back to camp."
This session, Blue Star isn't taking any chances. Kids showing up with fevers are sent home. At the mess hall, sharing is out and hand sanitizer is in.
"Always use the antibacterial and wash your hands before you eat," recited camper Mason Redler. "I'll try my best."
Camps for kids with health conditions like muscular dystrophy or asthma have shut down altogether so as not to put more vulnerable children at risk.