The investigators are now trying to seek access to hundreds of thousands of blood samples from the city that China has not so far let them examine.

The lead investigator for the WHO mission, Peter Ben Embarek, told CNN in a wide-ranging interview that the mission had found several signs of the more wide-ranging 2019 spread, including establishing for the first time there were over a dozen strains of the virus in Wuhan already in December.

Ben Embarek, who has just returned to Switzerland from Wuhan, told CNN: "The virus was circulating widely in Wuhan in December, which is a new finding."

The total number of global Novel Coronavirus cases has topped 108.7 million, while the deaths have surged to more than 2.39 million on Monday, the Johns Hopkins University said.

The University's Center for Systems Science and Engineering (CSSE) revealed that the current global caseload and death toll stood at 108,788,324 and 2,399,330, respectively.

The US is the worst-hit country with the world's highest number of cases and deaths at 27,639,317 and 485,332, respectively, according to the CSSE.

India comes in second place in terms of cases at 10,904,940.

The other countries with more than a million confirmed COVID-19 cases are Brazil (9,834,513), the UK (4,049,920), Russia (4,026,506), France (3,467,884) and Spain (3,056,035), the CSSE figures showed.

Brazil currently accounts for the second highest number of Covid-19 fatalities at 239,245, followed by Mexico (174,207) on the third place and India (155,642) on the fourth.

Meanwhile, the nations with a death toll above 30,000 were the UK (117,387), Italy (93,577), France (80,961), Russia (78,825), Germany (65,016), Spain (58,945) and Iran (58,945).