Public health experts and hundreds of doctors and scientists at home and abroad are urging the UK government to change its strategy against coronavirus, amid fears it will mean the epidemic “lets rip” through the population.

They say the UK is turning its back on strategies that have successfully brought down the numbers of infections and deaths in other countries.

On Thursday, Boris Johnson and his medical and scientific advisers announced that only those seriously ill in hospital would be tested. Anyone who had any symptoms should self-isolate at home for seven days, without notifying the NHS.

Banning mass gatherings would not help reduce the spread of infections, the prime minister and his advisers said – although it now seems likely, largely in response to sporting and entertainment bodies cancelling events of their own accord.

The UK’s Covid-19 strategy dangerously leaves too many questions unanswered | Anthony Costello Read more

Anthony Costello, a UK paediatrician and former director of the World Health Organization (WHO), said he had personally written to the chief medical officer, Professor Chris Whitty, asking for testing to continue in the community.

“The key principles from WHO are intensive surveillance,” he told the Guardian. “You test the population like crazy, find out where the cases are, immediately quarantine them and do contact tracing and get them out of the community. This deals with family clusters. That’s the key bedrock of getting this under control.”

This was how South Korea, China, Japan, Hong Kong and Taiwan had brought their case numbers down. “You can really take people out of the population and make sure they are quarantined. That is vital – before you get to social distancing.”

Yet the UK government was stopping tests outside of hospital. “For me and the WHO people I have spoken to, this is absolutely the wrong policy. It would mean it just lets rip,” he said.

Costello thinks we will be in the same position as Italy within two weeks. “The basic public health approach is playing second fiddle to mathematical modelling,” he said.

Dr Tedros Adhanom Ghebreyesus, WHO’s director general, expressed his deep concern on Friday at the end of testing and contact tracing in the UK and some other European countries.

“You can’t fight a virus if you don’t know where it is,” he said. “Find, isolate, test and treat every case to break the chains of Covid transmission. Every case we find and treat limits the expansion of the disease.”

Devi Sridhar, professor of global public health at The University of Edinburgh, listed on Twitter the reasons for continuing to test. “1 People can alter behaviour based on whether they have Covid. 2 Break chains of transmission. 3 Local hospitals can plan for how many patients will need care. 4 To know where cases are emerging (hotspots). 5 How do we know how large problem is?”

A government minister in Singapore has also expressed dismay. “One concern we have with cases such as UK and Switzerland isn’t just about the numbers. It is that these countries have abandoned any measure to contain or restrain the virus,” minister for national development, Lawrence Wong, said at a press briefing on Sunday. “If there’s no attempt to contain, we estimate the number of cases in these countries to rise significantly in the coming days and weeks.”

An open letter from a group including some of the UK’s most senior doctors asked the government to publish the modelling and any other evidence for the policies it is pursuing. “Our country’s public health response to Covid-19 is demonstrably different to most other countries’ responses globally and in Europe … There is also no clear indication that the UK’s response is being informed by experiences of other countries in containing the spread of Covid-19,” it said, pointing out the risks to the NHS of a rapid and huge surge in cases of people needing hospital treatment. The UK has 2.5 beds per 1,000 people in the population, they said, which is fewer than France (6), Italy (3.2) and the United States (2.8).

Immunologists, in a separate open letter, said they had “significant questions” about the government’s apparent strategy to rely on building up “herd immunity” by exposure to the virus in the UK. Sir Patrick Vallance, the chief scientific adviser, has suggested this might be a good outcome from many people becoming infected.

Herd immunity is usually brought about by vaccination – not exposing people to the risks of a disease. “The ultimate aim of herd immunity is to stop disease spread and protect the most vulnerable in society. However, this strategy only works to reduce serious disease if, when building that immunity, vulnerable individuals are protected from becoming ill, for example through social distancing. If not, the consequences could be severe,” says the letter from the British Society for Immunology.

Behavioural scientists joined the concern, saying they believed the government should immediately bring in social distancing measures and not delay for fear of the public getting “behavioural fatigue”.

“If ‘behavioural fatigue’ truly represents a key factor in the government’s decision to delay high-visibility interventions, we urge the government to share an adequate evidence base in support of that decision. If one is lacking, we urge the government to reconsider these decisions,” wrote Prof Ulrike Hahn from Birkbeck, University of London, and others.