US scientists have hailed a potential breakthrough in the coronavirus fight as a trial showed patients responding to an antiviral drug, fueling global hopes for a return to normal despite mounting deaths and abysmal economic news.

The medical news was enough to propel a rebound on Wall Street even after data showed the pandemic had plunged the United States into its worst economic slump in a decade and Germany predicted its biggest recession since the aftermath of World War II.

In the first proof of successful treatment against the illness that has claimed more than 226,000 lives, a clinical trial of the drug remdesivir showed that patients recovered about 30 percent faster than those on a placebo.

"The data shows that remdesivir has a clear-cut, significant, positive effect in diminishing the time to recovery," Anthony Fauci, the top US epidemiologist who oversaw the study, told reporters at the White House.

Fauci likened the finding to the first retrovirals that worked, albeit with modest success, against HIV in the 1980s.

The trial, which involved 1,063 people across 68 locations in the US, Europe and Asia, showed that "a drug can block this virus," Fauci said.

Remdesivir failed in trials against the Ebola virus and a smaller study, released last week by the World Health Organization, found limited effects among patients in Wuhan, China, where the illness was first detected last year.

Senior WHO official Michael Ryan declined to weigh in on the latest findings Wednesday, saying he had not reviewed the complete study.

"We are all hoping -- fervently hoping -- that one or more of the treatments currently under observation and under trial will result in altering clinical outcomes" and reducing deaths, he said.

The UN health agency said its emergency committee would meet Thursday for the first time since it declared coronavirus an international emergency three months ago.

US President Donald Trump has assailed the WHO as not responding quickly or aggressively enough, although critics say he is trying to deflect attention from his own response.

Itching to return to the campaign trail as he faces re-election, Trump announced he would resume travel next week with an event in the battleground state of Arizona -- but not yet resume rallies, when contagion remains a risk.

"Hopefully in the not too distant future we'll have some massive rallies and people will be sitting next to each other," he said.

US deaths shot past 60,000 on Wednesday. The United States has suffered the most deaths, with Britain's toll on Wednesday shooting up to the world's third worst at 26,097. 

More than 27,000 people have died in Italy.

- 'Unprecedented' contraction -

In the US, Florida became the latest place to move to reopen, with Republican  Governor Ron DeSantis saying restaurants will be able to serve customers outdoors from Monday if tables are at least six feet (1.8 meters) apart.

But experts have warned that only a full-scale vaccine will allow the wholescale removal of restrictions that put half of humanity under some form of lockdown.

Governments are nevertheless increasingly loosening the more suffocating rules in the face of the devastating impact of the crisis on the global economy.

The United States announced that economic output collapsed 4.8 percent in the first quarter, ending more than a decade of expansion.

Jerome Powell, chairman of the Federal Reserve, warned that economic activity will likely drop "at an unprecedented rate" in the second quarter -- grim news for Trump.

It will take "some time to get back to anything nearly resembling full employment," Powell told reporters.

Germany, Europe's largest economy, has succeeded in holding off the devastating death tolls seen elsewhere -- but is still bracing for an overwhelming economic hit.

Germany "will experience the worst recession in the history of the federal republic" founded in 1949, Economy Minister Peter Altmaier warned, predicting that GDP would shrink by a record 6.3 percent.

The International Labour Organization said half the global workforce -- around 1.6 billion people -- are in "immediate danger of having their livelihoods destroyed."

One of the worst-hit areas of the world economy is the aviation industry.

World air traffic suffered a massive drop of more than half in March compared with the same period last year, the "largest decline in recent history," the International Air Transport Association said.

US plane-builder Boeing announced plans to reduce its workforce by 10 percent and slash production of its main airliners while European aviation giant Airbus also reported big losses.

- Risks to children -

While the world keeps looking for signs of progress against the pandemic, research is also revealing frightening new details about the coronavirus.

Britain and France have both warned of a possible coronavirus-related syndrome emerging in children -- including abdominal pain and inflammation around the heart.

"I am taking this very seriously. We have absolutely no medical explanation at this stage," French Health Minister Olivier Veran said.

Experts have also warned of longer-term psychological tolls on both children and adults after weeks or even months in isolation.

- Britain adds care home deaths -

Unlike much of continental Europe, Britain has not unveiled a way to exit the lockdown. 

The sharp rise in its COVID-19 toll, which caused Britain to surpass Spain, came as it included deaths in places such as care homes for the first time.

British Prime Minister Boris Johnson initially resisted shutting down the country -- and himself became the highest-profile coronavirus patient, entering intensive care as he fought for his life.

He returned to work this week and on Wednesday became a father again when his partner Carrie Symonds gave birth to a boy.