Thread by @DiseaseEcology

While the overall argument in thread by @j_g_allen has merit (air travel is less dangerous than article suggests), he is incorrect about incubation periods (see Fig from meta-analysis: medrxiv.org/content/10.110…). 6.7% of inc periods are >14d & 2.5% are 18+d.

Thus, none of the cases can be ruled out due to long incubation periods. All are quite plausible.
Similarly, @j_g_allen argues that being on cruise ship or hotel could have led to infection. Possibly, but need data on infection in those settings to assess. None was given.

Finally, the absence of reported cases on flights is not evidence that transmission is not occurring. Many (most?) case investigators in US don't attempt to identify detailed source of travel-related cases.

Clear @j_g_allen is taking some heat for publishing op-ed suggesting air travel was low risk (washingtonpost.com/opinions/2020/…) due to 3 recent papers show evidence of in-flight transmission:
wwwnc.cdc.gov/eid/article/26…
wwwnc.cdc.gov/eid/article/26…
wwwnc.cdc.gov/eid/article/26…

Strongest actual argument for safety of air travel is last article above: when masks are worn and precautions are taken risk is low. There were 6 asymptomatically infected passengers on that flight & they infected only one person who took her mask off while in bathroom.

(Was low transmission due to lower infectiousness of asymptomatically infected people? That's a topic for another thread, but here's a paper by @nataliexdean et al w/ some suggestive evidence: medrxiv.org/content/10.110…)

What is needed to quantitatively assess real risk of air travel is large scale study w/ 100s of flights (not 1 or 2). Flights to country that has strict 14d quarantine would be ideal so post-flight exposure is low. Pre-flight risk still a possible counfounder, of course, and ...

transmission from people you travel with is also key counfounder, as was clear from study of train transmission of COVID: