Dr Margaret Chan, director-general of the World Health Organisation, did not mince her words.
The deadly Sars-like virus that has spread in recent months from the Middle East to Germany, France and the UK, killing more than half of those it has infected, is a "threat to the entire world".
Since it emerged in Saudi Arabia in September last year, the new virus has spread to 50 people in eight countries and claimed 33 lives.
Saudi Arabia said last night that three more people had died.
Addressing the World Health Assembly in Geneva last week, Chan said: "We understand too little about this virus when viewed against the magnitude of its potential threat. Any new disease that is emerging faster than our understanding is never under control.