WEDNESDAY, June 15 (HealthDay News) -- During the H1N1 flu pandemic of 2009, some people stopped flying out of fear of catching the virus while in the close quarters of an airplane cabin, but a new study shows that the "danger zone" for flu transmission is just a two-seat circumference around where you are sitting.

It had been thought that this hot zone was much larger, according to research published in the July issue of Emerging Infectious Diseases, a publication of the U.S. Centers for Disease Control and Prevention.

Scientists tracked illnesses among passengers on two long flights to Australia in May 2009, where several passengers were known to be infected with H1N1. Passengers were surveyed three months after arrival about any flu-like symptoms. Two percent of passengers had a flu-like illness during flight, and 5 percent (32) developed such an illness the week after they arrived at their destination.

Travelers were at a 3.6 percent increased risk for flu if they sat within two rows of a passenger with symptoms, and this risk jumped to 7.7 percent for those who sat within two seats of the sick passenger, the study showed. The two-seat danger zone refers to a sick passenger seated in the two seats in front of you, two seats behind you or two seats to either side of you.

Still, "it's not a given, but our 2x2x2 seats box is definitely the highest risk zone," said study author Dr. Paul M. Kelly, an associate professor at Australian National University in Canberra.

"Change seats if you find yourself within two seats of someone who is sneezing, coughing and looks like they have a fever," he said. "If you have a mask, wear it or suggest your neighbor wears it [and] wash your hands and avoid touching your own face to minimize the chances of spread via that route."

There are certain travel seasons that may be worse than others, he said. "Flu season is definitely the worst, and that is different in the northern (November-March) and the southern (June-September) hemispheres," Kelly said.

Dr. Michael Zimring, director of the Center for Wilderness and Travel Medicine at Mercy Medical Center in Baltimore, said the two biggest risk factors for getting the flu while flying are proximity to the sick passenger and the length of the flight.

The longer the flight, the greater the risk, he said. It is not the airplane air per se that ups the risk for flu transmission as airplanes do use air filters, which minimize the spread of germs.

"Infectious diseases such as the flu can pass via sneezing and/or coughing directly into someone's face or onto an object someone will come in contact with," Zimring said.

For example, "if someone coughs and the droplets land on a headrest or armrest, the next person touches that object and then eats with that same hand or touches ones face, the virus or bacteria passes from one to another," Zimring explained.

"The further you are away from the ill person, the less chance you will get the illness, and the shorter time you are exposed, the less chance you will contract that illness," he noted.

"Wash your hands frequently on the flight, especially if you are about to eat something, and remember the germs on the bathroom doorknob and the germs on the back of the seats as you hold on while you walk back to your seat," Zimring said.

"If you are in good health, got a good night's sleep and eat healthy, there is also less of a chance that you will get sick," he added.

Dr. Len Horovitz, a pulmonary specialist at Lenox Hill Hospital in New York City, agreed. "If you are worried, wear a mask," he said. "You will never see these people again so who cares if they think you are sick."

Viral particles can live on surfaces for 24 hours. "Always wash your hands before touching your face," he advised.

The air jets above the seats can also propel viral particles your way, Horovitz warned.

"These germs can travel up to seven feet on a subway and they probably go even farther on planes because of the mixing of the air by the overhead jets," he said.

Getting your flu shot each year can also lower your risk of developing the flu even if the passenger next to you coughs and sneezes for the whole flight, he said.

Dr. Neil Schachter, medical director of the respiratory care department at Mount Sinai Medical Center in New York City, said there have been a growing number of anecdotal reports that people develop upper respiratory infections (URI) after flights longer than five hours.

"While the study finds that the range of infection is no larger than two rows in each direction, there were several people with URI on each plane -- which certainly covered a large portion of the aircraft," Schachter said.

There have been several new infections in the past few years, including H1N1. "I think that increased surveillance of passengers is helpful to keeping sick passengers off the plane," he said. "We can anticipate emerging new infections, and better airport controls is certainly a step in the right direction, but this type of policy change takes time."

Until then, "I would advise my high-risk patients with underlying health problems to ask to be moved to another area if they are seated close to someone who is coughing and sneezing," Schachter said.

More information

There's more on protecting yourself from the flu at the U.S. Centers for Disease Control and Prevention.