ATLANTA (AP) — Let us give thanks — and pass the Purell.



Your family might be sharing more than turkey and pumpkin pie this Thanksgiving. Swine flu may also be on the table — and at crowded airports and shopping malls.



Just as the pandemic seems to be waning around the country, some health officials are worried that holiday gatherings could lead to more infections. So the government has launched a new travel-health campaign.



"It's important to remember the things that everybody can do to stay healthy," said Dr. Beth Bell of the Centers for Disease Control and Prevention.



Thanksgiving is typically followed by at least a modest bump in early seasonal flu cases, according to reports from the past few years. But this, of course, is not a typical year. Swine flu is a new virus that accounts for nearly all flu cases right now.



Despite weeks of declining infections, health officials are staying vigilant. The federal government is putting up posters in airports, seaports and border crossings in time for Thanksgiving. The campaign also includes advertisements with slogans such as "Stop, Wash & Go."



The CDC urges people to travel only if they are well, get vaccinated against swine and seasonal flu, wash their hands often, and cover coughs and sneezes with a tissue or sleeve.



Some 33 million Americans are expected to hit the nation's highways over the Thanksgiving holiday, a slight increase from last year. About 2.3 million more will travel by airplane.



The elbow-to-elbow conditions expected on many flights may pose more of an infection threat than a runny-nosed tike at the other end of a Thanksgiving dinner table. One CDC official even suggested asking that a sick passenger be moved to another part of a plane.



But that's not likely to happen on a crowded airliner or bus, and it isn't much of a solution anyway, said a few people waiting at Atlanta's downtown Greyhound station on Tuesday morning.



"That's just putting it next to somebody else," said Judd Nelson, 39, waiting to start a two-day bus trip to Phoenix.



Nelson had not been vaccinated against swine flu, and he did not have any hand sanitizer. He was resigned to his fate if someone with swine flu happens to be aboard his bus.



"The way I look at it is, if I get it, I'm going to get it no matter what," he said.



Swine flu has sickened an estimated 22 million Americans, hospitalized about 98,000 and killed 4,000 since it was first identified last April. It is similar to seasonal flu but poses a much bigger threat to children and young adults.



Usually, seasonal flu is just getting going in late November, and holiday get-togethers allow illness to jump from small pockets to other parts of the country. Swine flu, in contrast, has been widespread for months.



"It's not like we expect to see a bunch of infected people going to uninfected cities and towns," said Andrew Pekosz, a flu expert at Johns Hopkins University.



The swine flu pandemic hit in two waves: first in the spring, then a larger wave that started in the late summer.



For the past three weeks, fewer states have been reporting widespread cases. School closings have dropped to the point that there were none on Monday — the first time that's happened since late August — though there were six on Tuesday, according to the U.S. Department of Education.



But there are still plenty of ill people — as many as during the peak of many regular flu seasons, CDC officials say.



Indeed, disease trackers are quick to say that flu is unpredictable. A variety of things could happen, including a third wave or a mutation that could make the virus more deadly or less susceptible to medicines.



"We really don't know what the trajectory is going to be," said Bell, a CDC epidemiologist who has been a leader in the agency's swine flu response.



Seasonal flu usually emerges at this time of year, but some experts think swine flu will muscle aside the seasonal viruses. That probably will not be known until next month, said Dr. Richard Whitley, an infectious diseases specialist at the University of Alabama at Birmingham.



At New York's Pennsylvania Station, Katie Almroth was waiting to board a train Tuesday with her 11-month-old daughter Anna, who's been vaccinated for seasonal flu but not for swine flu. They were headed to Harrisburg, Pa., to visit relatives for Thanksgiving.



The 33-year-old nurse from Jersey City, N.J., said she was not worried about traveling during the swine flu pandemic, but felt more comfortable on a train than an airplane with her daughter.



"I must admit I did bring little wipes along," said Almroth, showing the antiseptic wipes she had tossed in her bag with small bottles of hand sanitizer.