Your Virus Odds on a Full Airplane

Assuming everyone on board wears a mask, your risk of contracting coronavirus on an every-seat-full flight is about 1 in 4,300, according to a professor at the prestigious Massachusetts Institute of Technology.

That’s considerably less than the odds of dying from being struck by lightning during your lifetime (1 in 180,746). And far less than the risk of a pedestrian being struck by a vehicle (1 in 541), cancer (1 in 7) or heart disease (1 in 6).

In a pre-print thesis, Arnold Barnett, the George Eastman professor of management science and statistics at the MIT Sloan School of Management, suggests that flyers may not face an overall severe risk from coronavirus on a commercial flight.

Barnett’s report presents a “rough” view of risk, and has not been certified through peer review. He writes: “But even a rough approximation of the risks at issue seems preferable to clashes of unsubstantiated conjectures. This paper strives for such an approximation, with an emphasis on the word ‘rough.’”

The MIT model does not factor in the possibility of exposure to the virus in the airport or while boarding or deplaning, nor the impact of going to and from an aircraft lavatory. He also did not attempt to factor boarding a plane in a high-risk area, Miami for example, compared to a low-risk area.

A meta-analysis in the medical journal, The Lancet estimated that mask wearing cuts transmission risk from 17.4% to 3.1%. Barnett also noted if there were a layer of plexiglass between passengers, as some have proposed, transmission risk would essentially drop to near zero.

The MIT professor considered three questions:

1. What is the probability that a given passenger on board is contagious with Covid-19?
2. What is the probability that universal masking can prevent a contagious passenger from spreading the disease?
3. How does the risk of infection depend on the locations on the aircraft of both the contagious and uninfected passenger?

The professor suggests that there could be a lower risk of contracting Covid-19 if middle seats remain open through the pandemic; 1-in-7,700. Barnett asks, “The question is whether relinquishing one-third of seating capacity is too high a price to pay for the added precaution.” Also, Barnett projects the risk of catching the virus for a passenger in a window seat on a packed aircraft at a similar 1 in 7,000.

In a pre-Covid-19 study (2018) by researchers at Emory University in Atlanta, they concluded: "A droplet-mediated respiratory infectious disease is unlikely to be directly transmitted beyond one meter from the infectious passenger. Thus, transmission is limited to one row in front of or in back of an infectious passenger.”

Dr Julian Tang, consultant virologist at the Leicester Royal Infirmary and associate professor at Leicester University, UK, offered similar sentiments: “Most of the transmission during a plane journey will be those short-range face-to-face conversations. Close-range aerosol transmission is what you have to be worried about on a plane, train or a bus – this is the biggest risk."

Barnett noted that “data from late June 2020 imply that approximately 1 in 120 Americans have Covid-19 on a given day (i.e., 40,000 confirmed cases per day x 10 x 7 days is about 1/120 of the US population of 330,000,000). Thus, it is not clear that the risk of getting infected during a flight is any higher than the risk associated with everyday activities during the pandemic.”

Many airlines are attempting to screen out potential passengers who are showing symptoms of the virus – through temperature screening, even quick-result swabs in the airport, thus minimizing the likelihood of someone onboard being ill and spreading Covid-19 or other illnesses. As many people are asymptomatic, of course, it cannot be known without testing if a fellow passenger is carrying the virus.

Good advice: wear a mask in the airport, while boarding/deplaning, and during the flight. And don’t talk, read a book.

To review Professor Barnett’s formula, his thesis can be found here.