The risk of inflight Covid-19 transmission is low, provided passengers remain masked throughout the flight and maintain social distancing when boarding and deplaning, according to a study this week by Harvard University's public health school.
The study, conducted by the Harvard T.H. Chan School of Public Health's Aviation Public Health Initiative and sponsored by a consortium of airlines, airplane manufacturers and airport operators, indicated that airlines' air-circulation practices are effective at virus filtration and echo results announced this month of a U.S. Transportation Command study.
Researchers pointed to planes' inflight air exchange and high-efficiency particulate air filtration practices as able to remove more than 99 percent of particles containing the virus from the air.
"Our team found that, together with their high-performing ventilation systems, the actions that the airlines put in place—including mandatory use of face masks—significantly reduce risks of viral transmission aboard an airplane," APHI co-director Leonard Marcus said in a statement. "With comprehensive adherence to these preventive measures by airlines and passengers, air travel, along with other sectors of society, can responsibly return to some level of normal activity as we await development of an effective vaccine."
The study examined current airline transmission mitigation efforts and modeled inflight virus transmission to reach its conclusions, according to researchers.
The study cited universal mask-wearing—save for brief periods of eating and drinking—maintaining social distancing while boarding and deplaning, providing pre-flight passenger health attestations and maintaining hand cleanliness as key measures to limit inflight virus spread.
Researchers considered the gate-to-gate inflight experience for this phase of the study; a second phase will examine the "curb-to-curb" experience, according to the report.
Researcher Refutes IATA Calculations
Meanwhile, a University of Alabama infectious disease specialist who co-authored a study of inflight transmission has rebutted the International Air Transport Association's interpretation of the included statistics. IATA's contention that there have been 44 confirmed cases of inflight transmission among 1.2 billion passengers—a ratio of one passenger in 27 million—is "bad math," Dr. David Freedman told Reuters.
"1.2 billion passengers during 2020 is not a fair denominator because hardly anybody was tested. How do you know how many people really got infected?" he said. "The absence of evidence is not evidence of absence."
IATA defended the calculation to Reuters, calling the figure a "relevant and credible" sign of low risk without claiming it is a "definitive and absolute number."
Another recent report, however, details the inflight infection of 13 passengers on a summer 7.5-hour flight into Ireland. The report published in European infectious disease journal Eurosurveillance detailed the infection of the 13 passengers on a commercial flight with 48 passengers and 12 crew on a plane with 283 seats. Nine of the infected passengers were wearing masks, one—a one-year-old—was not, with status unknown for the other three.
The passengers were from three different continents, according to the report, all connecting at a "large international airport" for the flight to Ireland. Neither the airline, flight origin or destination nor the exact date of the flight were specified. The report links further spread to 46 more people in Ireland from the 13 passengers.