May 22, 2020, ©. Leeham News: In our Corner series about flying during the COVID-19 pandemic, we look closer at the available research around passengers that fly with virus infections and if these spread to other passengers during a flight.
How much do we know and what are guesses?
What statistics are available around COVID-19 infections in airliners?
There were several studies available on virus infections (especially SARS but also seasonal flu) before IATA (the airline association) started searching the market for data around COVID-19 infections during airliner flights.
Most studies were around the spreading of SARS, a Coronavirus illness similar to COVID-19 (The COVID-19 disease is caused by the virus named SARS-CoV-2), with others analyzing the spreading of normal flu.
The studies, except for a couple, had the same result. Infection during flight passenger to passenger did not happen.
One SARS study had infections of co-passengers, as had an earlier flu survey. The infected passenger had in both cases a developed illness and coughed/sneezed repeatedly during the flight without wearing a mask.
From Figure 1, we can understand what happened. The strong jet of unprotected sneezing/coughing can overpower the orderly downdraught of the cabin air.
But these studies are exceptions (the SARS study was from 2003 with the flu study made earlier).
IATA has collected additional statistics around the present COVID-19 pandemic from its member airlines.
The results are informal, as only two scientific studies have been published regarding COVID-19 so far. IATA initially surveyed 18 larger airlines and then 70 of its airlines, representing half of the global passenger traffic.
The result from the two published studies and the 18+70 informal IATA surveys are the same. No passenger to passenger transmission of COVID-19 was found.
Three suspected passengers to cabin crew infections were reported and four pilot to pilot infections. In the latter case, the risk period included ground layovers for the pilots.
The passenger to cabin crew infections show the increased risk for a cabin crew when it leans into an unprotected passenger’s breathing when serving meals in a seat-aisle.
The published studies are one from Canada, where a long-haul flight with a confirmed COVID infected passenger resulted in no further infected passengers. Another report analyzes a flight on 31 March from the USA to Taipei with had 12 infected passengers on the flight. It generated no new cases from the 328 other passengers and crew members. All have subsequently tested negative.
Why is the risk of a passenger to passenger infection low?
We have discussed this briefly in the first article. We will dig deeper into this aspect in the next Corner.