Researchers: Over a thousand may have been infected with viruses

So far, 41 disease cases have been reported in China, according to the country's authorities. The center of the epidemic is the city of Wuhan, where a fish market was closed after the virus was derived.

But the number of infected may be over 1,700, according to a report from the Center for Global Analysis of Infectious Diseases (MRC) at Imperial College London. Among other things, the Department provides advice to the World Health Organization (WHO).

So far, three cases of illness have been registered outside China, two in Thailand and one in Japan.

"The fact that three cases have spread from Wuhan to other countries should mean that there would be many more cases than what has been reported," Professor Neil Ferguson, one of the authors of the report, told the BBC.

MRC estimates that at least 1,723 people had been infected in Wuhan until January 12, based on passenger figures from Wuhan Airport and disease outbreaks.

Neil Ferguson tells the BBC that he is much more concerned now than a week ago, though it is still too early to press the alarm button. He also says that the possibility that the virus can be spread from human to human should be taken more seriously because it is "unlikely" that the virus has only spread from animals to humans.

So far, two people in China have died of lung disease. The virus belongs to the same family as the deadly SARS virus, which caused more than 750 deaths worldwide 2003-2004 since the epidemic spread from China.