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.
Ryan added that data does not currently support health officials declaring the virus a global pandemic.
"If we say there's a pandemic of coronavirus, we're essentially accepting that every human on the planet will be exposed to that virus," he said. "The data does not support that as yet and China have clearly shown that that's not necessarily the natural outcome of this event if we take action, if we move quickly, if we do the things we need to do."
Health officials have said the respiratory disease is capable of spreading through human-to-human contact, droplets carried through sneezing and coughing and germs left on inanimate objects. The virus appears to be particularly troublesome for older people and those with underlying health conditions, health officials have said. Symptoms can include a sore throat, runny nose, fever or pneumonia and can progress all the way to multiple organ failure or death in some severe cases, they said.
Dr. Maria Van Kerkhove, head of WHO's emerging diseases and zoonosis unit, said that right now scientists believe there's no reason to think the virus would act differently in different climate settings.
— CNBC's Will Feuer and Noah Higgins-Dunn contributed to this article.