ST. LOUIS—Mention swine flu to a young child, and odds are pretty good you’ll get a blank stare.

But an increasing number of kids can tell you that the Sesame Street character “Elmo” sneezes properly into the crook of his arm, and if they sing the whole “ABCs” song while washing their hands they’ll get them really clean. They’re also well acquainted with hand sanitizer, anti-bacterial wipes—and their germ-fighting abilities.

Children may not understand what H1N1 influenza is, but about 1 in 5 in the U.S. already had a flulike illness in October, according to a telephone survey released by the Centers for Disease Control and Prevention. Doctors and childcare specialists believe kids, even young ones, have a role to play in limiting the spread of the virus that surfaced earlier this year and is a threat to young people.

“I don’t think it can be solely their responsibility, but partnering with them and their families on their health can only be a good thing,” said Dr. Alexis Elward, medical director of infection control for St. Louis Children’s Hospital, which has put in place the strictest disease prevention measures in staffers’ memory.

At the hospital on Monday, several patients in the playroom—and the adults with them—wore protective paper masks while they painted wooden toys or hovered over a “Thomas the Train” playset. The hospital is considering plans to broadcast a party over closed-circuit televisions this year, to keep hundreds from gathering together at the celebration to turn on the holiday lights.

“We’re balancing risk versus benefit,” Elward said.

Zachary Biggs, 7, of Chester, Ill., was staying at the hospital after having chin surgery. At his age, some H1N1 education had taken hold.

“If you get the swine flu, you have to come to the hospital and get medicine. You have to wash your hands, so you don’t get it,” he said. He added that he’s trying to keep his hands away from his nose, mouth and eyes to keep germs ay bay, and: “You can sneeze into a tissue, and then you should throw it away.”

Day cares and schools are also newly focused on preventing the flu’s spread. Children as young as 2 1/2 can understand the fundamentals, said Linda Smith, executive director of the National Association of Child Care Resource and Referral Agencies.

At Kiddie Academy in Lakewood Ranch, Fla., staff are washing children’s hands more frequently and teaching kids to sing while they use soap to make sure hands are well scrubbed.

Kids there and elsewhere are singing their alphabet or two rounds of “Happy Birthday” to make sure they spend enough time at the sink.

Cleaning crews are paying more attention to thorough washings of door handles, while toys that wind up in mouths are quickly rerouted for a cleaning before children play with them again, said the preschool’s assistant director Tina Pouso.

Some of the finer points of flu-prevention hygiene are newly acquired knowledge for the younger set—and the Muppets have been part of their sharp learning curve.

Sesame Street characters Elmo and Rosita are featured in new public service announcements, where the furry monsters show children how to sneeze into the elbow area of their arm. In another, Elmo and Luis talk to parents about creating a plan so they can keep children at home if they get sick.

“They’re easy messages, fun and make a difference,” said Jeanette Betancourt, outreach and educational practices vice president for Sesame Workshop, which was approached by the Centers for Disease Control and the U.S. Department of Health and Human Services.