Can flying make you sick?

On an American Airlines flight last week from New York to Seattle, traveler Jim Sullivan noticed the flight attendants preparing to serve a meal. He grabbed a bottle of hand cleanser and began wiping down the tray table in front of him. "A flight attendant I know told me how filthy these things are," he says.

Indeed, at a time when airplanes are often packed to capacity with travelers from around the world, it's no wonder that travelers start to worry about their exposure to germs and disease. With headlines warning of bird flu and cruise-ship outbreaks, passengers are more nervous than ever about who -- and what -- is really sharing their seat space.

But surprisingly, travel health experts say airplanes typically don't pose any bigger health or germ exposure risk than any other public place. The best advice to stay healthy while flying: wash hands often and drink lots of bottled water. Here are answers to some common questions about the health risks of travel and what airlines are doing to battle germs on board.

Q: Can I catch an illness from the passenger sitting next to me or from germs left by a sick passenger on the flight before me?

Travelers can catch an illness just from being on a plane, but it's not likely, says Marlene Zuk, an evolutionary biologist at the University of California-Riverside who studies the interaction between diseases and their hosts. "They're more likely to catch something at work because they're coming in closer contact with their co-workers." And, just sitting in a seat that an ill person has been in isn't likely to get you sick. The human body is constantly bombarded with microbes, Dr. Zuk says, most of which the immune system fights off.

There is a risk to having spray particles land on you (such as from a sneeze), since they can enter your body if you wipe that area of your skin on your nose or eyes. Respiratory droplets can't penetrate your skin, though, Dr. Zuk says. Experts recommend carrying hand gels to clean your hands in case you can't use the restroom. If you're sitting next to someone who's sick, you can ask to be reseated. Several airlines say that if there's a seat available, they will reseat passengers upon request.

Q: How often do airlines clean their planes? What about pillows and blankets?

For the most part, only surface cleaning is done at the gate. American Airlines says that different work is done depending on the mileage flown and the ground time available, but that it mostly involves picking up trash, folding blankets and replenishing provisions. British Airways says that it cleans its seats, replaces the headrests and vacuums the floors, in addition to other measures after every flight. Northwest Airlines says its aircraft undergo an additional cleaning every night, which includes vacuuming, cleaning windows and wiping down bins and other surfaces.

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