A fist bump may be American athletes’ greeting of choice as they try to avoid illnesses that might wreck their Olympic dreams.

Airplane illnesses and the rigors of long-haul travel are bigger concerns for Team USA’s medical team than any sporting injuries Michael Phelps and Tyson Gay may suffer on the way to London for the 2012 summer games.

Cindy Chang, chief medical officer for the 529-member U.S. contingent, told athletes to take aisle seats so they can take regular walks and do stretching routines in the galley so their muscles don’t seize up aboard the jets carrying them across the Atlantic. Team USA won’t snub an extended hand of friendship, said Chang, who also works as head physician for the University of California, Berkeley teams, suggesting athletes may break with conventional handshakes.

“A fist bump is the greeting,” said Chang with a laugh in an interview at the Olympic Village. “There are sanitary places all over that you can use. What you don’t want to do is shake someone’s hands and then touch your eyes or touch your nose and touch your face.”

Athletes from more than 200 nations are landing in the city ahead of the July 27 opening ceremony. Housing at the Olympic Village is dense, with as many as 16,000 competitors and officials staying in 11 residential areas. Most will share leisure facilities, while others will share a bedroom.

Around 3,300 people are expected to arrive at the Village Tuesday, London 2012 officials told reporters at a briefing. About 40 percent of the residences were occupied Monday.

“A cough can spread organisms 10 feet away from you, diseases can be spread by touching, coughing and sneezing,” Ron Cutler, director of biomedical science degree programs at London’s Queen Mary University, said. “Use soap and warm water. This is a once-in-a-lifetime moment and you don’t want to be spreading diseases to your colleagues.”

Nic Stevenson, a spokesman for Britain’s Civil Aviation Authority, said airlines use filters to try to remove bacteria and viruses from the air passengers breathe.

“These filters are similar to those used in the hospital operating theatres,” he said. “The total volume of cabin air is exchanged every two to three minutes compared with every five to ten minutes in most air conditioned buildings.”

Chang’s team of 80 doctors is on hand to dispense advice on anything from the safety of London’s drinking water to getting into a regular sleeping pattern.

“Even before they got off the plane we talk to them about how they can adjust their sleep cycle because it’s eight hours for some of them,” said Chang. “We tell them to stay up the night before so they can be tired when they get here.”

Britain, the host nation, has told its Olympians to avoid shaking hands with officials and to minimize contact with friends and family, according to the country’s chief medical officer Ian McCurdie. The 542-member British Olympic Team will use hand foam made by Procter & Gamble’s Vicks brand during their stay.

“The greatest threat to performance is illness and injury,” he said in a March 6 interview. “The Olympic environment is a hostile one. Housing can be dense, you share rooms and restaurants with many other athletes and there is a lot of extra stress. Most bugs you pick up on your hands, so hand washing is absolutely critical.”

— With assistance from Maria Tadeo and Eleanor Lawrie in London.