For weeks, WHO officials spoke during daily briefings in Geneva of a ``window of opportunity'' to try to contain the spread of the virus. But lately there have been indications that the containment window has closed.

Sources tell Reuters that earlier in March, elite hackers tried to hack into World Health Organization amid more than a two-fold increase in cyberattacks.

A higher risk assessment doesn't immediately warrant more or different action from countries, one WHO official said.

This type of coronavirus was first detected in December in the Chinese city of Wuhan.

The Olympics open on July 24, just under six months away.

All international travellers arriving in Toronto, Montreal and Vancouver international airports will be asked additional screening questions.