Having a little look at what Vietnam did to arrest the spread of Covid-19, since it's done so well. On March 7 (so more than two weeks before the UK lockdown) they instituted a categorisation system, rating infectees and their contacts from F0 to F5.

F0 means you're the guy with the positive test - you go to hospital regardless of symptoms. F1 means you're a direct contact, so it's off to central quarantine for you. But many *F2s* - contacts of F1s were centrally quarantined too, making up for limited testing capacity.

F3s cease travel and are required to isolate at home with regular temperature checks. People all the way down to F5 - (four degrees of separation from the case!) are advised to do isolation at home.

So by May 1st, you had a cumulative 270 cases (many flown in from overseas) but 70,000 stays in government quarantine facilities and 140,000 instances of hotel or home isolation.