"Let me be blunt, too many countries are headed in the wrong direction, the virus remains public enemy number one," WHO Director General Tedros Adhanom Ghebreyesus told a virtual briefing from the UN agency’s headquarters in Geneva.

"If basics are not followed, the only way this pandemic is going to go — it is going to get worse and worse and worse."

Global infections stand at 13 million, according to a Reuters tally, with more than half a million deaths.

Tedros, whose leadership has been heavily criticised by US President Donald Trump, said that of 230,000 new cases on Sunday, 80% were from 10 nations, and 50% from just two countries.

The United States and Brazil are the countries worst hit.

"There will be no return to the old normal for the foreseeable future ... There is a lot to be concerned about," Tedros added, in some of his strongest comments of recent weeks.

Tedros said the WHO had still not received formal notification of the US pullout announced by Trump. The US president says the WHO pandered to China, where the Covid-19 disease was first detected, at the start of the crisis.

Trump, who wore a protective face mask for the first time in public at the weekend, has himself been accused by political opponents of not taking the coronavirus seriously enough, something he denies.

A WHO advance team has gone to China to investigate the origins of the new coronavirus, first discovered in the city of Wuhan. The team’s members are in quarantine, as per standard procedure, before they begin work with Chinese scientists, WHO emergencies head Mike Ryan said.