It could have had strict quarantine rules, testing of arrivals, isolation of arrivals, contact tracing of arrivals, all justified by common sense and UK expert advice
And from when? Mass testing of arrivals wasn’t possible for quite some time. An infrastructure for contact tracing would have been nice, will agree on that.
That said, the WHO never recommended strict quarantines. At best, Feb. 29 WHO guidelines merely asked visitors to monitor themselves and report to health authorities if they had a problem:
Travellers returning from affected areas should self-monitor for symptoms for 14 days and follow national protocols of receiving countries
Also of interest:
Countries are reminded of the purpose of the International Health Regulations to prevent, protect against, control and provide a public health response to the international spread of disease in ways that are commensurate with and restricted to public health risks, and which avoid unnecessary interference with international traffic and trade. Countries implementing additional health measures which significantly interfere with international traffic are required to provide to WHO, within 48 hours of implementation, the public health rationale and relevant scientific information for the measures implemented
www.who.int/news-room/articles-detail/updated-who-recommendations-for-international-traffic-in-relation-to-covid-19-outbreak
The WHO is still very lukewarm on travel bans and such, it should be said. But since they are politically popular 🤷♀️