The number of people already infected by the mystery virus emerging in China is far greater than official figures suggest, scientists have told the BBC, APA reports.
There have been more than 60 confirmed cases of the new coronavirus, but UK experts estimate a figure nearer 1,700.
Two people are known to have died from the respiratory illness, which appeared in Wuhan city in December.
"I am substantially more concerned than I was a week ago," disease outbreak scientist Prof Neil Ferguson, said.
The work was conducted by the MRC Centre for Global Infectious Disease Analysis at Imperial College London, which advises bodies including the UK government and the World Health Organization (WHO).