US scientists have hailed a potential breakthrough in the coronavirus fight as a trial showed patients responding to an antiviral drug, fuelling 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.

"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.

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