The World Health Organisation’s chief has warned that "the worst is yet ahead of us" in the coronavirus pandemic.
WHO director-general Tedros Adhanom Ghebreyesus did not specify why he believes the outbreak could get worse, but he and others have previously pointed to the likely spread of the illness through Africa, where health systems are less developed.
His remarks will likely revive alarm, just as many countries ease restrictive measures aimed at reducing the spread of the virus that has infected 2.5 million people and killed more than 166,000.
"Trust us. The worst is yet ahead of us," he told reporters from WHO headquarters in Geneva. "Let's prevent this tragedy. It's a virus that many people still don't understand."
Some Asian and European governments have gradually eased or started relaxing lockdown measures like quarantines, school and business closures and restrictions on public gatherings, citing a decline in the growth of Covid-19 case counts and deaths.
Mr Tedros and his agency have been on the defensive after President Donald Trump of the US - the WHO's biggest single donor - last week ordered a halt to US funding for the agency.
The US leader alleged that the organisation botched the early response to the outbreak.
Among other things, Mr Trump insisted the WHO had failed to adequately share "in a timely and transparent" way information about the outbreak after it erupted in China late last year.
Mr Tedros said: "There is no secret in WHO because keeping things confidential or secret is dangerous. It's a health issue.
"This virus is dangerous. It exploits cracks between us when we have differences."
He said US Centres for Disease Control and Prevention staff have been seconded to work with his agency, suggesting that was a sign of the WHO's transparency.
"Having CDC staff means there is nothing hidden from the US from day one" Mr Tedros said. "Our CDC colleagues also know that we give information immediately to anyone."
In one of his starkest comparisons yet, the UN health agency chief also alluded to the Spanish Flu more than a century ago.
He said the coronavirus has a "very dangerous combination... like the 1918 flu that killed up to 100 million people".
Mr Tedros called the illness "Public Enemy Number One" and said: "We have been warning from day one: this is a devil that everybody should fight."
