Context: In recent years, new commercial aircraft have been designed to recirculate approximately 50% of the cabin air to increase fuel efficiency. Some older aircraft use only fresh air. Whether air recirculation increases the transmission of infectious disease is unknown; some studies have demonstrated higher rates of the common cold among persons working in buildings that recirculate air.
Objective: To evaluate the role of air recirculation as a predictor of postflight upper respiratory tract infections (URIs).
Design, setting, and participants: A natural experiment conducted among 1100 passengers departing the San Francisco Bay area in California and traveling to Denver, Colo, during January through early April 1999, and who completed a questionnaire in the boarding area and a follow-up telephone interview 5 to 7 days later. Forty-seven percent traveled aboard airplanes using 100% fresh air for ventilation, and 53% traveled aboard aircraft that recirculated cabin air.
Main outcome measure: Incidence of reporting new URI symptoms within 1 week of the flight.
Results: Passengers on airplanes that did and did not recirculate air had similar rates of postflight respiratory symptoms. The rates of reporting a cold were 19% vs 21% (P =.34); a runny nose and a cold, 10% vs 11%, (P =.70); and an aggregation of 8 URI symptoms, 3% in both groups (P>.99). Results were similar after statistical adjustment for potential confounders.
Conclusion: We found no evidence that aircraft cabin air recirculation increases the risk for URI symptoms in passengers traveling aboard commercial jets.