Doctors Debate Role of Air Travel in Spreading Respiratory Illnesses

On larger planes, cabin air is recycled, filtered and then mixed with fresh air. However, not all planes are equipped with filters.

As the holiday travel season takes off today, you might have more than a few pounds to worry about when you land back home -- like the flu, a cold or some other respiratory infection.

Flier, beware? Doctors debate the extent to which air travel plays a role in spreading common respiratory illnesses, and the evidence seems to cut both ways. The airline industry insists air cabins are no worse than other crowded places where the healthy and sick mingle. But most experts agree that being cooped up next to a coughing, sneezing person is not good for your health.

"I seem to have a lot of people who come in from air flights who have common colds," said David Joseph, a family practice doctor and chairman of the board of Austin Diagnostic Clinic. "You put a lot of people in a small area, and it's hard to avoid the risk of respiratory illness."

Joseph, however, questioned whether the airplane cabin is any worse than other crowded, indoor environments. His colleague, Dr. Sujata Jere, said breathing recirculated airplane air can't cause a person to get sick, but sitting next to someone who is sick certainly can. Changing seats is a good idea, but it's less of an option these days when the airlines are selling out so many flights.

Dr. Roy Welker, director of Travel Medicine Services at Brigham and Women's Hospital in Boston, has a different take. He said he thinks that air in plane cabins is a problem, and that a healthy person doesn't need to be sitting next to a sick one to pick up a bug.

"You're more likely to get it from people very near you, but you can get it from people elsewhere in the airplane," too, Welker said. Colds and flu are most likely, he said, but more serious respiratory illnesses have been known to spread on aircraft. The U.S. Centers for Disease Control and Prevention have documented tuberculosis spread among airplane passengers, and several severe acute respiratory syndrome infections are thought to have occurred during plane travel.

The spread of disease in aircraft cabins is difficult to determine, Dr. Mark Gendreau of the Lahey Clinic in Burlington, Mass., said in congressional testimony earlier this year. He testified that flights of eight or more hours were more likely to cause problems for healthy people sitting within two rows of the sick person. There were notable exceptions, he said, including a SARS outbreak on an Air China flight that lasted only three hours and affected passengers seated seven rows in front and five rows behind the sick person.

On larger planes, cabin air is recycled, filtered and then mixed with fresh air. Not all planes are equipped with filters, and Welker said that over the past decade, the amount of fresh air has been reduced because of energy costs associated with warming cold outside air at high altitudes.

The Air Transport Association of America, a trade association for commercial airlines, said that airlines have increased the amount of recirculated air to boost fuel efficiency but that passenger health is not at risk. In most large aircraft, about half of the air is recirculated, and the other half comes from the outside, said Katherine Andrus, the association's assistant general counsel.

"There is nothing about aircraft cabin environment that makes it any easier to catch an illness from other people" than in other enclosed spaces, Andrus said.

A 2002 study by researchers at the University of California at San Francisco said that passengers in planes with recirculated air reported no more colds than people flying in planes using all fresh air. If anything, Andrus said, the 50-50 mix makes the cabin air less dry and more comfortable.

The recycled air is cleaned by high-efficiency particulate air filters on most planes. She did not know what percentage of planes have the filters, but the Government Accountability Office reported in January 2004 that 85 percent of the planes with a capacity of more than 100 passengers already use the filters.

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