How quickly the unthinkable can become reality. We are all entering a new world as the Covid-19 pandemic takes hold. Many more families in the UK will lose loved ones, the prime minister has warned: while 590 cases have been identified, officials say the true number is probably between 5 and 10,000. The government has now moved from trying to contain the outbreak, to seeking to delay it. It says it is doing so on the advice of experts. Yet there are questions about whether its policy is adequate. The editor of the medical journal the Lancet describes it as complacent. Some experts had already warned that the initial UK response had been “pathetic”.

The new measures to achieve delay are minimal compared to those taken in other countries. In Italy, more than 1,000 have now succumbed. The old and other vulnerable groups will suffer. The overstretched NHS is surely not prepared for the numbers who will be falling sick in short order.

In stark contrast, Ireland has shut down schools, nurseries and colleges and urged all who can to work from home. Denmark has sent home all non-critical public sector employees. Norway is poised to adopt what it describes as the most far-reaching measures ever experienced in peacetime. India has suspended most visas for foreigners. Israel has ordered all arrivals into a fortnight’s quarantine. Italy, with more than 12,000 cases, has imposed a countrywide lockdown.

The dedication of scientists, health workers and others around the world is inspiring. But it is governments who determine the context in which they operate, and who steer the public response. Around the world, authorities are being forced to make difficult and complex decisions in this crisis. Mass quarantines of the kinds seen in Wuhan, China and Italy, may not be the only or even the best approach; it appears aggressive testing and contact tracing with some social distancing measures have been effective in countries including Singapore and South Korea (which has been testing 20,000 people a day).

Yet the UK appears to have disregarded lessons from elsewhere, and be set on another course. It will no longer test those not sick enough to be in hospital, simply relying on those who feel unwell to stay at home for a week (a much shorter period than other places have imposed). Its focus on urging those with flu-like symptoms to self-isolate comes as new research suggests that most Covid-19 infections may be spread by people who have caught it but not yet developed symptoms.

It is essential that governments follow expert medical advice and give clear instructions. While some have done exemplary work, others are failing. The complacency and erratic nature of the American response has been shocking and frightening. A ban on almost all foreigners flying from most European countries does nothing to address its existing outbreak. On top of systemic problems such as healthcare coverage and the lack of statutory sick pay, there is a glaring shortage of testing, even for those at clear risk: the number of US cases is likely far higher than declared. Donald Trump maximised the damage by misrepresenting his own plan, leaving the public confused, and classifying coronavirus discussions. Others are taking matters into their own hands – with universities sending students home, companies ordering staff to work from home, and even the NBA suspending its season.

But for the UK too there are questions. The head of the World Health Organisation this week called on states to take “urgent and aggressive action”, noting that several countries have successfully suppressed the virus, at least for now. The challenge for others, he added, “is not whether they can do the same – it’s whether they will”. Apparently the UK will not. If Boris Johnson’s judgment is wrong, the price will be a high one.