Another lockdown could be avoided, a spokesperson for the WHO said, but only if the UK and other European countries provide far more help to those affected, and ensured they complied.
“Make it genuinely possible for them to self-isolate,” Margaret Harris said, pointing to the need for people to work, or have time off, obtain food and help family members in need.
But she added: “They also need to hear from authorities every day, checking up on them, so they have a sense that they really are in a special situation.”
Ms Harris added: “I have seen in east Asia that, if somebody is asked to self-isolate, all those things are put in place and they are called and monitored and followed up.
“And we are also seeing in east Asia that those countries have been more successful.”
The call comes amid mounting criticism of the government for lacking an exit strategy from ever-tougher restrictions, with a warning shot fired by a 50-strong group of northern MPs.
Scientists have warned that the tier 3 restrictions imposed across a swathe of the north will fail to cut rising infections to a low enough level to allow those regions to escape the harsh measures.
However, any move to toughen self-isolation requirements would put Mr Johnson on a collision course with many Tory MPs – who resent even the current curbs on freedom.
Ms Harris said the prospects for many countries were “grim”, with the possible consolation that infections were largely among younger age groups that are less likely to become seriously ill.
“We may not see the terrible, terrible rise in deaths that we saw in April,” she told BBC Radio Four.
“But it doesn’t mean that our healthcare systems won’t be under dreadful pressure.”
She urged leaders to recognise that it was “not easy” for people to follow orders to self-isolate – after the UK government introduced huge fines for ignoring such instructions.
“If helped to do this, they will do this,” Ms Harris said – but not if it was “just a poster, or a piece of information, and nobody is taking it seriously.”
Local political leaders have repeatedly criticised the government for failing to give proper compensation to workers who are required to self-isolate.
Mr Johnson was left red-faced after wrongly claiming they receive £500 each week. In fact, only a single £500 payment is available – and it is only paid to low-earners.