The world has entered uncharted territory in its battle against the deadly coronavirus, the UN health agency warned, as new infections dropped dramatically in China on Tuesday but surged abroad with the US death toll rising to six.
Globally, the virus has killed more than 3,100 people and infected over 90,000 even as a clear shift in the crisis emerges, with nine times as many cases recorded outside China as inside, according to the WHO.
China has imposed draconian quarantines and travel restrictions to keep large swathes of the population indoors for weeks, a strategy that appears to have paid off as new cases have been generally falling for days.
While Italy has locked down towns, other countries have stopped short of imposing mass quarantines and instead have discouraged large gatherings, delayed sporting events and banned arrivals from virus-hit nations.
Twitter told staff across the world to work from home.
South Korea, Iran and Italy have emerged as major COVID-19 hotspots, which is believed to have started at a market that sold wild animals in the central Chinese city of Wuhan late last year.
With concerns growing about its impact on the global economy, G7 finance ministers and central bank chiefs will hold talks on the issue on Tuesday.
South Korea, the biggest cluster outside China, approached 5,000 cases on Tuesday as 477 new infections were reported, with two more fatalities taking its death toll to 28.
"The entire country has entered a war with the infectious disease," South Korean President Moon Jae-in said.
By contrast, China reported 125 new cases on Tuesday -- its lowest daily increase in six weeks -- with all but 11 infections in Hubei province, of which Wuhan is the capital.
The nationwide death toll rose to 2,943 with 31 more deaths, all in Hubei, with some 80,000 total cases.
China is even importing infections now, with 13 confirmed so far, including eight Chinese nationals who had worked at the same restaurant in northern Italy's Lombardy region.
"We are in uncharted territory," WHO chief Tedros Adhanom Ghebreyesus said on Monday.
"We have never before seen a respiratory pathogen that is capable of community transmission, but which can also be contained with the right measures."
Community transmission means infections within a population are not imported from another virus-hit area.
The United States is now facing a potential epidemic, with six people dying in the northwestern state of Washington, where officials warned residents the battle against the disease was shifting from containment to mitigation.
"The risk for all of us of becoming infected will be increasing," said Jeff Duchin, a health officer in King County where five of the deaths occurred.
The county has more than two million residents and is home to Seattle, a major commercial and transportation hub.
The White House, which has been accused of downplaying the threat from the virus, struck a bullish tone.
Vice President Mike Pence declared that a treatment "could literally be available by this summer, or early fall".
He was likely referring to remdesivir, an antiviral drug developed by the pharmaceutical firm Gilead that has already been used to treat one US patient and was moving toward two expansive final stage trials in Asia.
Pence also announced American pharmaceuticals were forming a consortium to fight the virus, and that South Korea and Italy would screen all their airline passengers bound for the US.
Despite its world-class hospitals and cutting-edge research, the US is viewed as vulnerable to an epidemic because of glaring disparities in healthcare availability, with nearly 28 million people without coverage.
Chinese officials have touted progress in their own battle against the epidemic, and in another sign of growing confidence, 19 provinces resumed inter-provincial bus services on Sunday, according to state media.
But the restrictions have hammered the world's second-largest economy and threatened to cut into global growth.
After tanking last week, most Asian stock markets were up on Tuesday following a surge on Wall Street as governments and central banks said they would step in if needed to soften the blow.
Australia's central bank slashed interest rates to a record low on Tuesday.
UN medical experts arrived in Iran on Monday to help tackle the world's second-deadliest coronavirus outbreak, with 66 fatalities and more than 1,500 infections.
In Italy, tourist hotpots including the Duomo in Milan reopened to visitors but access was limited to avoid overcrowding.
Italy, Europe's worst-affected country with around 1,700 infections, said Monday its deaths from the virus had jumped 18 to 52.
The WHO says the virus appears to particularly hit people over the age of 60 and those already weakened by other illnesses.
Its mortality rate is between two and five percent -- higher than the seasonal flu.