Market panic over the fast-spreading new coronavirus is uncalled for, the World Health Organization's director-general said Sunday as governments around the world rush to contain its spread.

"Global markets … should calm down and try to see the reality," Tedros Adhanom Ghebreyesus told CNBC's Hadley Gamble during a panel discussion at the King Salman Humanitarian Aid Center's International Humanitarian Forum in Riyadh. "We need to continue to be rational. Irrationality doesn't help. We need to deal with the facts."

The comments come after global stocks were slammed in their worst week since the 2008 financial crisis. The Dow Jones plunged a whopping 3,500 points across the week, more than 12%, its largest weekly point loss ever and biggest percentage drop in 12 years.

The deadly virus, which originated in China, has spread to more than 60 countries and killed at least 2,943 people. More than 85,000 people have been infected.