Officials confirmed that the new mystery virus can spread between humans and said 15 medical staff have now been infected, stoking fears about an international pandemic and prompting airport authorities around the world to step up screening of travellers arriving from China.

While the United Nations health agency said it needed more comprehensive information to confirm precisely the type of pathogen causing the infections, it said a new coronavirus was a possibility.

Chinese scientists have found all the genetic building blocks of the deadly SARS virus in a single population of horseshoe bats.