Calculating in-flight transmission risks
While the airlines tout their HEPA filters, which scrub more than 99 percent of germs in the air, there has been very little data on the risks of catching coronavirus in-flight, even as evidence emerges that respiratory droplets containing live virus may linger in the air in indoor spaces. To date, no super-spreading events have been traced to a flight.
German researchers recently published a study in the JAMA Network on a group of 24 tourists in March who were unwittingly exposed to Covid-19 in Israel a week before flying to Frankfurt on a four-hour-and-40-minute flight carrying 102 passengers. They found two likely cases of virus transmission on the flight, both seated within two rows of an infected passenger. Notably, no one was wearing masks on this flight, which took place before that public health mandate was adopted by airlines beginning in May in the United States.
On June 8, when The New York Times surveyed 511 epidemiologists about when they would travel again by airplane, the largest contingent, 44 percent, said in three to 12 months. They deemed other activities, including attending a sporting event, concert, funeral or wedding, as riskier.
The question of whether a middle seat left open would improve a passenger’s odds of not getting sick compelled Arnold Barnett, a statistician and professor of management science at Massachusetts Institute of Technology, to look into it.
“United said it was a P.R. strategy and not about safety, whereas Delta went to the other extreme,” he said.
His mathematical model multiplied the number of Covid-19 cases by 10, based on the Centers for Disease Control and Prevention’s estimate that the number of undetected cases could be 10 times the known infection rate. He factored in the barrier created by seat backs, the in-flight air purification systems and the effectiveness of masks in stopping contagion, which he said was about a four-in-five chance.
He found that on a fully loaded flight, the chance of contracting Covid-19 was one in 4,300. If the middle seat is empty, the risk falls to one in 7,700. Taking into account the possibility of spreading the virus to others not on the plane, he estimated the death risk to be one per 400,000 passengers on full flights and one in 600,000 with open middle seats.