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Airlines have strongly insisted it was safe to fly during the coronavirus pandemic, and travel to the United States is increasing ahead of the Thanksgiving holiday despite a nationwide increase in cases of the virus.
Still, America’s top infectious disease experts say the findings behind the carriers’ safety claims are not so conclusive.
Concerned about the “misinterpretation” of their results, researchers in a Defense Department study widely cited by industry have added a caveat. A seasoned travel health expert declined to attend an airline trade group press conference, citing what he called their “miscalculations.”
“The airline industry has gotten a bit ahead of itself in trying to say the risk is zero,” said David Freedman, professor emeritus at the University of Alabama at Birmingham who was hesitant to attending an International Air Transport Association event that cited his work.
U.S. airlines, hit by an unprecedented drop in demand since the virus began to spread widely in March, are enjoying their strongest week since then. Even as health officials warn against travel during the Thanksgiving holiday due to an increase in the number of covid-19 cases, more than 4 million people have passed through airports between Friday and Monday.
The risk of getting infected with the novel coronavirus on airplanes, which have highly effective filters that remove the virus from the air and where the use of a mask is required, is likely quite low, scientists say.
But the research is far from clear and some recent cases have documented transmission on flights even when passengers wore masks and were seated far from each other, according to a review of recent cases and interviews with academics and disease specialists.
“I can certainly say that it is premature to say that air travel is very safe,” said Qingyan Chen, an engineering professor at Purdue University in Indiana who has written extensively on disease transmission by plane.
Airlines officials, responding to the historic drop in passenger numbers, have repeatedly defended infection protections on flights.
“Flying is safe,” Nicholas Calio, president of Airlines for America, a trade group for major carriers, said in a briefing Nov. 12. “I will declare it categorically.”
A4A declined to add additional comments. He highlighted efforts to force passengers to wear masks and stay separate when boarding and exiting, and to disinfect planes. Montreal-based IATA defended its use of Freedman’s data on confirmed in-flight transmissions, saying it had never called the results final.
A4A frequently cited a study from the Harvard TH Chan School of Public Health, which was funded by the trade group and other sources in the aviation industry, which concluded that the risk of transmission on an airliner was “very weak”. But the authors warned their screenings depended on compliance with mask use, and also urged airlines to improve ventilation while planes are parked at the gate.
Another study mentioned by the airlines was conducted by the Department of Defense with help from United Airlines Holdings Inc. and Boeing Co. It attempted to measure how viral aerosol particles were exhaled by a simulated masked passenger.
United said in promotional material released Oct. 15 that the study “determined that the risk is almost non-existent.”
However, after media coverage of the study, the authors added a revision, saying they were “concerned about possible misinterpretation of the results.” They also admitted to having based their results on a person exhaling relatively few viral particles, an amount well below documented levels in some cases.
Airplane filters and the use of the mask “dramatically reduce” exposure to infectious aerosols, they wrote. “However, the current scientific understanding of the transmission dynamics of SARS-CoV-2 is not sufficient to calculate the definitive risk of SARS-CoV-2 transmission from these measurements of aerosol transport.”
United spokeswoman Leslie Scott responded in an email that “throughout the pandemic, our top priority has been the health and safety of our customers and our crew.”
“That’s why we have supported military officials, medical experts and aviation engineers in their work to demonstrate that aircraft cabins are among the safest in public indoor environments through advanced air filtration systems, the mask wearing and diligent cleaning protocols, ”she added.
Overall, there are few confirmed reports of infections linked to thefts. However, due to limited contact tracing in the United States and the difficulty in finding cases of transmission, it is difficult to say for sure what this means, the researchers said.
“I haven’t seen any study come out and say it’s very risky,” said Byron Jones, an engineering professor at Kansas State University who has studied airliner aviation safety. “But I haven’t seen the study that says it’s definitely safe either.”
The US Centers for Disease Control sums up the risks of air travel this way on its website: “Most viruses and other germs are not easily spread on flights because of the way the air is circulated. and is filtered on planes. However, it’s difficult to keep your distance on crowded flights, and sitting within six feet of others, sometimes for hours, can increase your risk of contracting covid-19 . “
While some studies have shown cases in which no one on a flight has been infected despite the presence of contagious passengers, other data have documented in-flight transmissions.
Chen of Purdue said he was following reports in China of a possible infection between passengers on a Nov. 9 Air China flight from Los Angeles to Tianjin.
Ten people who were not connected to each other and resided in different parts of the United States tested positive for the coronavirus after arriving. All passengers had tested negative for the disease before the flight, suggesting that at least some of the transmission occurred on the plane, he said.
Such incidents are puzzling because they seem to contradict Chen’s previous research showing that the use of masks can significantly reduce the risk of infection, he said.
“This is why I have doubts about what happens on planes,” he said.
Irish government researchers have documented as many as 13 cases linked to a single theft last summer, according to an article published in October. The infections in five of the cases were genetically related, “strongly suggesting a single point source of infection,” the authors said.
The widebody was largely empty, people were spaced out on the plane, and almost everyone whose activity could be documented said they were wearing masks. Nevertheless, the authors estimated that 10-18% of passengers were infected.
“Interestingly, four of the flight cases were not seated next to any other positive cases, had no contact in the transit room, wore face masks in flight and would not be considered close contact. according to current guidelines from the European Disease Center Prevention and Control, ”the authors said.
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