Or perhaps it is the contrary Red and the decision not to stop flights is political.
Yes. Probably in the absence of evidence, I'd agree. However there would have to have been a discussion with experts on this to a certain extent too, because the political implications of large numbers of people testing positive who had just come into the country would be hugely damaging. It has to be a political decision based on the probability of the number of COVID-19 entries being very low to begin with. Otherwise the political decision to keep flights backfires massively. It has the potential to cause mass outrage and panic (which is destablising in its own right).
But given now the evidence to stop flights doesn't seem to be there either, from that information coming out of the US, that decision does appear to be generally proportionate and justify not stopping them.
There doesn't seem to be a mass of evidence to suggest that screening has completely failed.
Now this could, yet in time, prove to be utterly naive and a huge number of cases have gone undetected only for random clusters of the virus to pop up unexpectedly all over the place.
But we now have no idea if this will have come directly from China either.
What about the person who travels to Nigeria, infects a bunch of people there, and then someone travels from Nigeria to the UK or to the US and starts an outbreak?
Ultimately a travel ban has very obvious limitations. You can't ignore the possibility of an indirect infection from a cluster in a third party country with low health care standards.
Do we close the borders to everywhere but places with high quality health care services and good infection control handling procedures?
Its the debate about what is effective and what is proportionate. Is it effective to completely close the border merely to China? At this point, I think its highly debatable.
In the case of China, given to enter the UK you have to have a visa and funds to travel if you are a Chinese citizen, there is an economic barrier here which might have some impact. It self limits the number of Chinese citizens who can actively travel and the UK have the power to restrict visas more opaquely and with less political fallout if they feel the need.