Going back to earlier pages - I think the reason they are pinpointing Myanmar, Cambodia etc is that they assume the virus is spreading there but they don’t have the resources to test, count infections or treat. All are popular places with Chinese tourists.
Secondly, I’m sure the govt is making a decision between three options: the “Chinese model” where they have to take steps to close schools, close businesses, lockdown whole areas, restrict travel etc. Very hard to do in the U.K. with a less compliant population.
Or two is to just let the virus run wild, tell people to stay home if they’re sick but basically do nothing apart from that - much like seasonal flu advice, only go to hospital if their symptoms get really bad.
And option 3 is a halfway house - encourage only essential travel, close large gatherings, stop sporting events etc but no hard lockdown.
Over here in Australia we had a terrible flu back in winter 2017 - huge numbers got it, it flew through schools, children and pregnant women died (not in huge numbers but still). Yet we had no restrictions, no school closures, nothing. My son got it mildly as he had been vaccinated and at our school we had classes with 50% of children off - at one point I think 40% of our whole junior school (of 350 children!) were away. So clearly it was serious and yet there was nothing like the response to this virus which seems much milder.