Although everyone is checking symptoms and temperature before granting entry these days, that may be tilting at windmills.* The virus is mostly spread before symptoms begin, which is the insidious, menacing truth that makes this so much worse than regular flu.
Quantitative COVID-19 infectiousness estimate correlating with viral shedding and culturability suggests 68% pre-symptomatic transmissions.
"The profile suggests that a 68.4% (95% CI: 67.0-69.7%) of the infections are caused by infections before the symptoms appear..."
Temporal dynamics in viral shedding and transmissibility of COVID-19
"We estimated that 44%(95% confidence interval, 25–69%) of secondary cases were infected during the index cases' presymptomatic stage..."
Temporal dynamics in viral shedding and transmissibility of COVID-19
"We estimated that 44% (95% confidence interval, 25–69%) of secondary cases were infected during the index cases' presymptomatic stage"
And a substantial proportion of people have a puzzling absence of symptoms throughout their infection. (The Diamond Princess was a perfect crucible in which to study virus transmission in detail in an isolated population.)
Estimating the asymptomatic proportion of coronavirus disease 2019 (COVID-19) cases on board the Diamond Princess cruise ship, Yokohama, Japan, 2020
"The estimated asymptomatic proportion was 17.9% (95% credible interval (CrI): 15.5–20.2%). Most infections occurred before the quarantine start."
-Tom
* I love that quaint expression "tilting at windmills"
https://en.m.wiktionary.org/wiki/tilt_at_windmills#:~:text=(intransitive)%20To%20attack%20imaginary%20enemies,engage%20in%20a%20futile%20activity.
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