The World Health Organisation has repeated calls for all countries to find and test every coronavirus case after the British government claimed the practice was “no longer necessary”.

Announcing the next stage of the UK’s strategy, the chief medical officer for England said on Thursday that only hospital patients would now be formally checked for the virus.

“It is no longer necessary for us to identify every case and we will move from having testing mainly done in homes and outpatients and walk-in centres, to a situation where people who are remaining at home do not need testing,” Professor Chris Whitty added.

The plan puts Britain at odds with international advice issued by WHO, which repeated appeals for efforts to track and trace all coronavirus cases on Friday.

Addressing a press briefing, director-general Dr Tedros Adhanom Ghebreyesus said: “You can’t fight a virus if you don’t know where it is. Find, isolate, test and treat every case, to break the chains of transmission.

“Every case we find and treat limits the expansion of the disease.”

Around 800 people have tested positive for coronavirus so far in the UK, out of 32,771 checked, but the government's chief scientific adviser said the actual number of people infected could be between 5,000 and 10,000. Eleven patients with coronavirus have died in the UK.

Globally, the current outbreak has killed more than 5,000 people and more than 132,000 cases have been reported in 123 countries.

Europe has become the epicentre of the global pandemic, with more cases now being reported every day than seen in China at the height of its epidemic.

But Britain’s approach has diverged from other countries, including Italy, France and Spain, who are imposing more stringent measures to reduce contact between members of the public.

Following a meeting of the government’s emergency Cobra committee on Thursday, Boris Johnson announced the UK was moving from the “contain” to “delay” part of its plan.

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He did not announce a ban on mass gatherings, although scores of major sporting and cultural events have already been suspended by organisers and it is believed that the government is now drafting legislation to halt big events.

Emergency legislation bringing in enhanced powers will be published next week and there could also be a move towards more people working from home.

Chief scientific adviser Sir Patrick Vallance said the government's approach to tackling coronavirus hopes to create a “herd immunity” to the disease.

But WHO spokesperson Dr Margaret Harris said: “We don't know enough about the science of this virus, it hasn't been in our population for long enough for us to know what it does in immunological terms.

Jeremy Hunt criticises government's approach to coronavirus

"Every virus functions differently in your body and stimulates a different immunological profile," she said, speaking on BBC Radio 4's Today programme on Saturday.

“We can talk theories, but at the moment we are really facing a situation where we have got to look at action.”

Sir Patrick said modelling predicted a 20 to 25 per cent reduction in the peak of the epidemic through official advice for people to stay at home for a week if they have mild symptoms.

Moving to whole household isolation adds an extra 25 per cent reduction, while preventing the elderly from getting infected could reduce death rates by 20 to 30 per cent, he added.

Helen Whately, the care minister, insisted the government was “following the evidence”.

“As the chief medical officer said, and I have been advised, the evidence tells us that stopping mass gatherings doesn't have a huge impact on the spread of the virus,” she told the BBC.

But Dr Tedros called on all nations to take comprehensive action, after hitting out at a lack of “political commitment” to tackling coronavirus in unnamed countries.

“Our message to countries continues to be: you must take a comprehensive approach,” he said.

“Not testing alone. Not contact tracing alone. Not quarantine alone. Not social distancing alone. Do it all.

“Any country that looks at the experience of other countries with large epidemics and thinks ‘that won’t happen to us’ is making a deadly mistake. It can happen to any country.”

Dr Tedros called on countries do to everything possible to reduce transmission by quarantining people who had contact with infected people.