You’re going to see a lot about a new CDC-released study that suggests blocking middle seats is important protection for air travel during the pandemic. However the coverage is going to be very misleading.
All that the new research tells us is that being a bit farther away from someone infected with the virus is probably better than being right next to them, which we already know.
However here’s a typical tweet from a CNN correspondent.
BREAKING: New CDC modeling suggests EMPTY MIDDLE SEATS on commercial flights cuts coronavirus transmission by 23 to 57 percent.
With Delta changing its policy, all major U.S. airlines will sell every seat starting May 1. pic.twitter.com/EDDSbLWbpR
— Pete Muntean (@petemuntean) April 14, 2021
This Study Doesn’t Model Covid-19 Infection At All
The first and most important thing is that the study is very explicit that it is not modeling virus transmission at all, just exposure (“It is important to recognize that the current study addresses only exposure and not transmission”). So any reporting that suggests a reduction in the number of Covid-19 cases from blocked middle seats is using the research wrong.
Researchers used spray bottles in an airplane cabin mockup to disperse bacteriophage MS2, which is a single strand RNA virus similar to a norovirus. A five-row section of a Boeing 737 fuselage, and an 11-row mockup of a Boeing 767 cabin, were used. These didn’t have engines, so actual cabin filtration was replaced by “conditioned air in the laboratory.”
What The Study Actually Tries To Show
Aerosol dispersion was measured and the researchers developed a model for whether someone would be exposed in a the cabin. In other words, they built a model to see how much distance would matter for exposure if you were near someone who was a source of the virus.
Of course right now perhaps 1 in 200 Americans are actively infected with the Covid-19 virus. (Based on a rough estimate of the number of actual infections versus identified infections and an average length of time infected.) A majority of those won’t spread the virus to others.
So if there was someone actively infected on one out of every two or three flights – it’s not likely that many, because some infected people will be less likely to fly because of symptoms – then a “single passenger who was in the same row and two seats away from the SARS-COV-2 source, rather than in an adjacent middle seat” would see a “23% exposure reduction.”
In other words, a blocked middle seat might help those seated around the infected person a little bit, but the piece tells us nothing about how much this changes the risk of spreading the virus.
Mask Wearing Isn’t Accounted For In The Research
The study talks about the rate of cabin air refresh and use of HEPA filtration, but uses that to assume aerosols are limited to spreading several rows from an infected passenger. The study doesn’t measure the extent to which those measures are preventive of infection. And it doesn’t appear to take into account the downward direction of air flow.
It also doesn’t factor any role that masking plays in reducing virus exposure or infection, and doesn’t consider at all to what extent vaccination matters for whether blocking middle seats presents a public health good or not.
Anti-maskers will also find something to like in the study, which justifies their ignoring the role of masks because “masks are more effective at reducing fomite and droplet exposures than aerosol exposures.” If you’re promoting this study for blocking middle seats, you’re also arguing against the effectiveness of masks against aerosol transmission of a virus.
Transmission Can Happen, It Seems Rare, And Not A Big Issue For The Vaccinated
Covid-19 does seem to spread on planes, but is rare certainly compared to other indoor congregant settings. If you’re vaccinated this probably isn’t something to be worried about. But the study may cause you to want to buy an empty middle seat next to you for your next flight.