World Health Organisation (WHO) experts said on Tuesday that studies show people with coronavirus are most infectious just at the point they begin to feel unwell.

Dr Mike Ryan, WHO's top emergencies expert, said the novel coronavirus lodges in the upper respiratory tract, making it easier to transmit by droplets than related viruses such as Sars or Mers, which are in the lower tract.

"That means you could be in the restaurant feeling perfectly well and start to get a fever, you are feeling okay, you didn't think to stay home, but that's the moment at which your viral load could be actually quite high," he said.