The head of the World Health Organization (WHO) warned Monday that the “worst is yet ahead us” from the novel coronavirus outbreak.

WHO Director General Tedros Adhanom Ghebreyesus said in a video conference that the world must act together on a national and global scale to overcome the pandemic.

He reiterated his calls for global solidarity and national unity and warned that if this does not happen, more people will die.

“Without these two, believe us — the worst is waiting for us. Let’s prevent this tragedy. This is such a virus that many people haven’t understood it yet,”

Read more: WHO warns worst of coronavirus yet to come