An Australian government study has found that fear of catching infectious bugs when flying is widely exaggerated.
The belief that the air in planes is full of contaminants is based on the perception that it is continually recycled with limited input from outside, the Australian Transport Safety Bureau said in a report released Tuesday.
But if recirculation and filtration systems are working properly, the risk from flying -- as far as bugs are concerned at least -- should be no worse than travelling by bus or eating in a restaurant, the study suggests.
"The risk of transmission of infection on board an aircraft is probably no greater than, and perhaps less than, other environments where large numbers of people are gathered together," it says.
The bureau noted that the emergence of severe acute respiratory syndrome (SARS) in 2002 and recent outbreaks of bird flu in Asia had increased concerns about the risks of air travel.
Infectious diseases reported to have been transmitted on board an aircraft include influenza, tuberculosis and SARS, it said.
But considering the number of flights each day, such cases occurred relatively infrequently.
There was also evidence that most of the victims had been infected by sitting close to a sick passenger and being exposed to droplets from sneezing or coughing rather than from contaminated recirculated air, the study found.
Outside air entering an aircraft cabin at altitude is essentially sterile and the airflow pattern and frequent air exchanges minimise the spread of infections, the report said.
In modern aircraft the airflow is from the top of the cabin down to the floor, where it is vented and either exhausted or re-circulated.
"The ventilation system is usually designed so that air entering the cabin at a given seat row is exhausted at the same seat row.
"This limits the amount of air flowing towards the front and back of the aircraft," the bureau said.