World Health Organization officials said Friday they are increasing the risk assessment of the coronavirus, which has spread to at least 49 countries in a matter of weeks, to "very high" at a global level.

"We are on the highest level of alert or highest level of risk assessment in terms of spread and in terms of impact," said Dr. Mike Ryan, executive director of WHO's health emergencies program. The group isn't trying to alarm or scare people, he said. "This is a reality check for every government on the planet: Wake up. Get ready. This virus may be on its way and you need to be ready. You have a duty to your citizens, you have a duty to the world to be ready."

The world can still avoid "the worst of it," but the increased risk assessment means the WHO's "level of concern is at its highest," he said at a press conference at WHO headquarters in Geneva.

World leaders still have a chance to contain the virus within their borders, Ryan said. "To wait, to be complacent to be caught unawares at this point, it's really not much of an excuse."

Outside China as of Friday morning, 4,351 cases across at least 48 countries have been confirmed, including 67 deaths, WHO Director-General Tedros Adhanom Ghebreyesus said. About two dozen countries have reported only one case.

He said most cases of COVID-19 can still be traced to known contacts or clusters of cases and there isn't any "evidence as yet that the virus is spreading freely in communities." That's one reason why WHO hasn't declared the outbreak a pandemic, Tedros said.

Denmark, Estonia, Lithuania, Netherlands and Nigeria all reported their first cases on Thursday, Tedros said. All these cases have links to Italy, he added.

Tedros reiterated that the virus could still turn into a pandemic. He urged against fear and panic, adding, "our greatest enemy right now is not the virus itself. It's fear, rumors and stigma."

On Wednesday, WHO officials said the number of new COVID-19 cases outside China exceeded those inside the country for the first time. Tedros said Thursday that countries must act "swiftly" and "aggressively" to contain the virus.

"With the right measures, it can be contained," he said at the time, adding countries should begin thinking about whether they have proper isolation units, medical supplies and other vital equipment.

Ryan told reporters that containing the virus and interrupting transmission give officials an opportunity to stop the virus.

"But what it's clearly doing as you've seen in China and Singapore, it's slowing the virus down and allowing us to get ready to prepare," he said.