The public health response to a serious epidemic is laid out simply and clearly by the World Health Organization (WHO). Test intensively, trace contacts, quarantine and maintain social distancing. When Covid-19 got out of control in Wuhan, after three weeks of public health inaction, the Chinese authorities mounted a proper campaign to control the virus. They listened to the WHO. They tested extensively, setting up mobile testing centres, and getting the test result time down from four days to four hours. They cut the time from onset of symptoms to lab result from 12 to three days. They identified family clusters (the virus spreads mainly through extended close contact so family members are most at risk) and arranged isolation centres for contacts.

Above all, they mobilised communities. They didn’t leave it all to messages and nudge behavioural methods. Yes, Wuhan was in lockdown, but across the country local authorities had high autonomy to help people abide by these best public health principles. This was not a terrorised population but one passionate about tackling an existential threat. They also used apps and smartphones to get messages across, to share information about local clusters and for data collection. Everyone in Wuhan, a city of 11 million, ordered their food online, and had it delivered. And the strategy worked. In seven weeks China stopped the epidemic in its tracks. It now reports only 10 to 20 new cases per day in a population of nearly 1.4 billion. Deaths have plummeted. Several other countries, including South Korea, Japan, Singapore and Taiwan, have copied this strategy, with local modifications, with similar results.

Now they realise they must face the challenge of how to loosen up, and whether allowing the economy to recover will lead to more outbreaks, but they have a nationwide system to jump on new clusters and outbreaks to keep this under control. The aim is to wait and hope for drugs and vaccines to emerge in the next 12 months to enable them to treat cases and to build proper herd immunity from a vaccine.

I had assumed that the UK would do the same, that the authorities would be building their resources and plans around nationwide testing, contact tracing, quarantine and a progressive policy of social distancing. I assumed they would inform the public they had a two- to three-month “contain and delay” strategy to get the epidemic under control, and mobilise communities everywhere to provide local support. But from the press conferences last week, the government is not following the WHO strategy. They appear to have concluded that it is inevitable most people would get the disease, so we should let the epidemic proceed to allow 60% of the population to become infected and build herd immunity through the wild virus. What is the scientific justification for this departure from WHO policy? I have questions:

Why have they abandoned population testing and contact tracing to identify and seclude clusters of infections? They recommend only testing cases in hospital. Won’t this strategy ensure that the spread of the virus is intense and will cause more infections and more deaths in the near term?

Why do they recommend self-isolation only for people with symptoms when Maria Van Kerkhove of the WHO reports that “it seems that people shed more virus in the early phases rather than the late phases of disease”? Asymptomatic contacts may be highly infectious, so they should be tested, isolated and followed up in the community. Will they set up quarantine centres to help those who have no family support or are homeless, or need social care?

What are their plans for national, district, municipal, village and community mobilisation? “Nudge” is not enough. We need to devolve power and autonomy to allow locally intelligent decisions around a coherent national strategy. What is their detailed strategy for screening of infected people in the home, and provision of CT scans for those with early signs of pneumonia and to identify those at high risk? Without an all-out national mobilisation for social distancing, are the behavioural and nudge strategies really evidence-based to flatten the peak? Or simply based on models?

Why are we emphasising herd immunity now? Does coronavirus induce strong herd immunity or is it like flu, where immunity remains weak and new strains emerge each year? We have much to learn about Covid-19 immune responses. Doesn’t this contradict WHO policy? Tedros Adhanom Ghebreyesus, WHO director-general, said after declaring a pandemic: “The idea that countries should shift from containment to mitigation is wrong and dangerous.”

Shouldn’t we wait to see the China situation? They have contained the epidemic after seven weeks of intensive national effort. Will epidemics break out again in new states? Maybe. Will their strengthened systems not contain them quickly and effectively? What is their herd immunity to date? We don’t have the data available but new tests are coming online. It might be substantial, without a massive epidemic.

The WHO policy – practised by China, South Korea, Singapore, Taiwan and Hong Kong – is to keep things damped down until drugs and a vaccine are available. Vaccines are a safer way to develop herd immunity, without the risks associated with the disease itself. Is it wise or ethical to adopt a policy that threatens immediate casualties on the basis of uncertain future benefit?

What is the policy to promote social distancing? How can we promote advice for families, mass gatherings, schools, workplaces, restaurants, theatres? And can we make it locally relevant? School closures might be phased depending on the intensity of transmission based on local data about clusters, as they did in Singapore. But we need testing and sharing of information online for local decisions.

Finally, on the precautionary principle, shouldn’t we go all out to damp this epidemic down, with all possible measures, whether evidence is strong, uncertain or weak, and worry about herd immunity when we have more evidence? The stated government policy is to allow 40 million people to become infected. This could mean 6 million hospital admissions, 2 million requiring special or intensive care, and 402,000 deaths if the chief medical officer Prof Chris Whitty’s 1% estimate of mortality is correct.

We can suppress this epidemic in the way that China and other countries have done. Then we can worry about how to loosen up, and hope that a vaccine comes onboard. But we need to act now. Every day of delay will mean more people become infected or die.

• Anthony Costello is professor of global health and sustainable development at University College London and a former director of maternal and child health at the WHO