(USA TODAY) -- Some time-honored traditions -- working sick, flying sick, going to school sick -- are in question as the nation seeks to fend off the spread of swine flu.

The federal Centers for Disease Control and Prevention, in its most specific calculation to date, estimated Thursday that the number of Americans who came down with the H1N1 virus in the first wave of the disease (April to July) could have been as high as 5.7 million. Swine flu is widespread in every state but Connecticut, New Jersey, South Carolina, Hawaii and the District of Columbia.

As a result, schools are questioning perfect attendance awards, employers are looking twice at sick-day limits, and airlines are encouraging the ticketed ill to stay on the ground.

Everywhere, the cry is the same: Wash your hands. Cover your mouth. Use your sleeve. On the street, the handshake is being supplanted by the fist dap and the elbow bump.

At the doctor's office, the competition for an appointment and a vaccination is intense.

"I've never seen it like this. ... That name, H1N1, sends parents into a panic," says Angela Gordon, administrator at Dunwoody Pediatrics in suburban Atlanta. "We've had a lot of verbal abuse."

Gordon says the practice's decision to reserve its vaccine supply for high-risk patients annoys some parents. "They say, 'So you refuse to give my child the H1N1 vaccine because they don't meet the criteria! If they catch it this weekend and die, we're going to blame you!' "

Prevention is selling well. Walgreens has seen increased sales of over-the-counter flu drugs, hand sanitizers, vitamins and face masks, said spokesman Robert Elfinger.

Fears that sick-but-steadfast students will show up for class are prompting schools to scuttle "perfect attendance" awards programs. In Leechburg, Pa., Principal Cynthia Portman eliminated her school's program this year because "parents had maybe sent their child when they weren't really well, because they were looking for that award."

Portman says the attendance award often goes to students who aren't the strongest academically -- whose "claim to fame is they are here every day."

Some companies are going out of their way to encourage ill workers to stay home. Chris Paradysz, CEO of New York City marketing agency PM Digital, says his firm never wants sick people at work, but adds: "Now, we are extra vigilant about making sure people don't come back before they're healthy."

Mike Epstein, a senior manager at Convergys, a company with nearly 75,000 employees, tells flu-stricken workers "if you're out of sick time, we'll work with (you)."

They had better take his offer: 83% of Americans say they'll snitch on co-workers who show up with flu symptoms, according to a Mansfield Communications survey.

Airlines -- aware that some travelers would rather fly sick than pay more -- are following long-standing policies to keep manifestly sick people off flights but also giving them a break.

A poll this month by TripAdvisor.com found that 51% of Americans would fly with the flu rather than pay a ticket-change fee.

AirTran Airways has resolved that conflict by offering to "gladly rebook any passenger with H1N1 with no penalty," says spokesman Christopher White. American Airlines says that if it refuses to board someone with a communicable illness, it will waive a rebooking fee.

The Roman Catholic Diocese of Lafayette, Ind., told parishes to stop shaking hands during the sign of peace and to remove holy water from church fonts.

Nothing is sacred. Boston Celtics basketball coach Doc Rivers, a "handshaker," is now more of a "fist bumper."

"I hope the fans understand," Rivers says.

Copyright 2009 USA TODAY, a division of Gannett Co. Inc.