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By John Toon
The bacterial communities accompanying airline passengers at 30,000 feet have a lot in common with the bacterial communities surrounding people in their homes and offices, according to a new study.
Using advanced sequencing technology, researchers studied the bacteria found on three components of an airliner cabin that are commonly touched by passengers: tray tables, seat belt buckles, and the handles of lavatory doors. They swabbed those items before and after ten transcontinental flights and also sampled air in the rear of the cabin during flight.
What they found was surprisingly unexciting.
“Airline passengers should not be frightened by sensational stories about germs on a plane,” says Vicki Stover Hertzberg, a professor in Emory University’s Nell Hodgson Woodruff School of Nursing and a coauthor of the study in Microbial Ecology. “They should recognize that microbes are everywhere and that an airplane is no better and no worse than an office building, a subway car, home, or a classroom. These environments all have microbiomes that look like places occupied by people.”
Given the unusual nature of an aircraft cabin, the researchers hadn’t known what to expect from their microbiome study. On transcontinental flights, passengers spend four or five hours in close proximity breathing a very dry mix of outdoor air and recycled cabin air that passes through special filters, similar to those found in operating rooms.
“There were reasons to believe that the communities of bacteria in an aircraft cabin might be different from those in other parts of the built environment, so it surprised me that what we found was very similar to what other researchers have found in homes and offices,” says Howard Weiss, a professor in Georgia Institute of Technology’s School of Mathematics and the study’s corresponding author. “What we found was bacterial communities that were mostly derived from human skin, the human mouth—and some environmental bacteria.”
The sampling found significant variations from flight to flight, which is consistent with the differences other researchers have found among the cars of passenger trains, Weiss notes. Each aircraft seemed to have its own microbiome, but the researchers did not detect statistically significant differences between preflight and post-flight conditions on the flights they studied.
“We identified a core airplane microbiome—the genera that were present in every sample we studied,” Weiss adds. The core microbiome included genera Propionibacterium, Burkholderia, Staphylococcus, and Strepococcus (oralis).
Though the study revealed bacteria common to other parts of the built environment, Weiss still suggests travelers exercise reasonable caution.
“I carry a bottle of hand sanitizer in my computer bag whenever I travel,” says Weiss. “It’s a good practice to wash or sanitize your hands, avoid touching your face, and get a flu shot every year.”
This new information on the aircraft microbiome provides a baseline for further study, and could lead to improved techniques for maintaining healthy aircraft.
“The finding that airplanes have their own unique microbiome should not be totally surprising since we have been exploring the unique microbiome of everything from humans to spacecraft to salt ponds in Australia. The study does have important implications for industrial cleaning and sterilization standards for airplanes,” says Christopher Dupont, another coauthor and an associate professor in the microbial and environmental genomics department at the J. Craig Venter Institute, which provided bioinformatics analysis of the study’s data.
The 229 samples researchers obtained from the aircraft cabin testing were subjected to 16S rRNA sequencing, which was done at the HudsonAlpha Institute for Biotechnology in Huntsville, Alabama. The small amount of genetic material captured on the swabs and air sampling limited the level of detail the testing could provide to identifying genera of bacteria, Weiss says.
In March, in the journal Proceedings of the National Academy of Sciences, the researchers reported on the results of another component of the FlyHealthy study that looked at potential transmission of respiratory viruses on aircraft. They found that an infectious passenger with influenza or other droplet-transmitted respiratory infection will most likely not transmit infection to passengers seated farther away than two seats laterally and one row in front or back on an aircraft.
That portion of the study was designed to assess rates and routes of possible infectious disease transmission during flights, using a model that combines estimated infectivity and patterns of contact among aircraft passengers and crew members to determine likelihood of infection. FlyHealthy team members monitored specific areas of the passenger cabin, developing information about contacts between passengers as they moved around.
Among next steps, the researchers would like to study the microbiome of airport areas, especially the departure lounges where passengers congregate before boarding. They would also like to study long-haul international flights in which passengers spend more time together—and are more likely to move about the cabin.
Additional coatuhors are from the HudsonAlpha Institute for Biotechnology and the Boeing Company. A contract between the Georgia Institute of Technology and the Boeing Company supported the work.
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