The “l(fā)eader of the free world” is traditionally a source of reassurance in times of crisis. But the current US president, Donald Trump, is providing confusion, not leadership. Instead of damping down the flames of the coronavirus outbreak, his Oval Office address on Wednesday poured fuel on them. The mood was hardly helped by the World Health Organization declaring the virus a pandemic the same evening. But Mr Trump’s 30-day ban on travel to America from most European countries triggered new record falls in markets on Thursday. With the global economy already struggling to avoid a recession, it dealt another sharp blow to confidence.

The US is not alone in imposing travel restrictions. India on Wednesday stopped issuing tourist visas. But WHO recommendations are clear: restricting movement of people and goods “is ineffective in most situations and may divert resources from other interventions”, as well as interrupting “needed aid and technical support”.

It is far from clear, moreover, whether Mr Trump’s ban will slow the US spread of the virus. While the president said a number of new clusters there were “seeded by travellers from Europe”, Covid-19 is already being spread between Americans who have had no connection with countries with high infection rates. Excluding the UK and Ireland from the travel ban, too, is puzzling. They lag behind most west European countries in infection rates per head of population, but are on a similar trajectory. Far more potentially effective than banning travel would have been steps to address the severe shortage of virus testing kits in the US.