PARIS, France — The sharp rise in cases and the geographical spread of the coronavirus outside China confirm WHO fears over dealing with the crisis, experts warned Sunday as they appealed for ever greater vigilance.

"There has been a profound shift in the direction that COVID-19 (new coronavirus) is taking over the past 48 hours," said Professor Devi Sridhar, Director of the Global Health Governance Programme at the University of Edinburgh Medical School.

"The WHO and its member state governments now need to be thinking about transitioning from containment to mitigation, ie. reducing the negative impacts of continued transmission," Sridhar warned. 

On Friday, World Health Organization (WHO) chief Tedros Adhanom Ghebreyesus had already sounded the alarm, saying the window to stem the virus was shrinking.

"We are still in a phase where containment is possible... our window of opportunity is narrowing," he warned, adding if countries did not quickly mobilise to counter the virus spread, matters could get "messy."

He also warned that Africa's poor health infrastructure left it vulnerable to the COVID-19 disease, which has spilled out of China to more than 25 countries.

Those fears have been compounded by three fatalities in recent days in Italy --  where some 50,000 people are in lockdown  -- eight in Iran and six in South Korea.

The WHO has expressed concern at the apparent emergence of cases without a clear epidemiological link to China, where it emerged.

'Anywhere in the world'

"It's what we call the passage to community transmission," said Professor Arnaud Fontanet, specialist in epidemiology of emerging diseases at France's Pasteur Institute.

"That renders controlling it much more difficult and presages the risk of its introduction beyond China."

Cases in both Lebanon and Canada appear to have emanated from Iran, for example, while, in Italy, scientists are puzzled that they cannot trace a link between several cases of sufferers with no apparent links to infected persons. 

"What is happening in Italy and South Korea and Iran could happen anywhere in the world," said Sridhar. 

Nathalie MacDermott, lecturer at King's College London, said "the evolving situation in South Korea, Iran and Italy is very concerning.

"There has been the expectation that some countries might develop person to person transmission of SARS-COV2 following an imported case of infection from an affected country.

"What is concerning is the lack of clear contact with such an individual in initiating clusters in these three countries, and particularly in Iran and Italy."

MacDermott urged all countries to take prompt action "to try and contain these clusters before there is dissemination to large proportions of the population."

"I think this is a new phase" in the propagation of the virus as new chains of transmission emerge from previously undetected cases, says Eric D'Ortenzio, epidemiologist at France's Inserm medical research institute.

He likewise urged increased surveillance for any potential emergence of home-grown cases as well as areas known to be already affected by the outbreak.