8/n (cont.) - The number of infectious people can be obtained by averaging new cases over 1 week for a state - Only 25% of infectious people on planes are infectious while they are travelling - COVID-19 cases are infectious for 7 days
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9/n Now, these range from completely absurd to somewhat reasonable. The infectious period of COVID-19, for example, is the source of much debate and 7 days is a not unreasonable estimate to use
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10/n The idea that masks reduce transmission by 82% on a flight is, however, totally without evidence. The reference is to a meta-analysis that looked primarily at studies of SARS and MERS and population cohorts over long periods of timepic.twitter.com/HYNkx2KfV6
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11/n We have, and I cannot stress this enough, ABSOLUTELY NO IDEA how much masks may reduce transmission on planes. It depends on how well they're used, how often, what masks, etc etc etc etc
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12/n Maybe 82% is the right number. But we have no way of knowing and thus as an assumption it's disastrous to the model If the number is instead 10%, the risk of transmission is 5x higher!
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13/n This situation is mirrored in other assumptions. The paper assumes that people on planes have half the risk of COVID-19 than everyone else, which is not referenced and seems to me wildly implausiblepic.twitter.com/Veqev0RWQ2
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14/n If we instead assume that people on planes are MORE likely to have COVID-19 - because they travel more! - suddenly the risk of transmission quadruples
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15/n If we recalculate the numbers changing just these two assumptions, the risk goes from a 1 in 4,300 for flying with middle seats filled to a 1 in 430 risk So, 10x riskier
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16/n If you were to repeat this process for every assumption - remember, there are over a dozen - you'd find that a realistic bound might be that the risk goes from 1 in 40 to 1 in 4,700 In other words: an ENORMOUS range
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17/n Now, to be clear, I actually don't think that the risk of getting COVID-19 while flying is 1 in 40, or even necessarily 1 in 4,700. I think that this risk is incredibly hard to quantify, because flying isn't just spending 2 hours on a plane
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18/n It's going to an airport, sitting in a lounge, queuing up for the bathroom, getting on the plane, picking up luggage etc etc etc
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19/n Now the risk to you of sitting near someone who has COVID-19 on a plane, based on contact tracing case series, is not 0, but it's hard to know exactly how big it is Unfortunately, this study tells us practically nothing about that number
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20/ Even worse, there is really no way from this research whether keeping the middle seat empty reduces risk or how much it might do that All of this is basically assumed
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