WHO officials made the announcement following two days of emergency committee meetings of health experts on the virus.
The coronavirus has infected more than 600 people worldwide, though mostly in China. As of Jan. 23, Chinese authorities have reported 17 deaths from the virus so far.
Cases have been reported in China, Thailand, South Korea, Taiwan, Japan and the United States. The virus causes a fever and, in some cases, difficulty breathing.
“Make no mistake, this is now an emergency in China, but this has not yet become a global health emergency,” said Dr. Tedros Adhanom Ghebreyesus, director-general of the WHO, on Thursday.
Ghebreyesus also provided some additional details on the virus and the people infected by it.
“We know that this virus can cause severe disease, and that it can kill, although for most people it causes milder symptoms,” he said. “We know that among those infected, one-quarter of patients have experienced severe disease.”
Most of the people who have died had underlying health conditions such as hypertension, diabetes or cardiovascular disease that weakened their immune systems, he said.
All this information would have been based on preliminary numbers and it is possible that there are other, milder cases which have not been officially diagnosed, suggested Dr. Isaac Bogoch, an infectious diseases specialist at Toronto General Hospital. “What we don’t really know is the denominator.”
While human-to-human transmission has been reported within China, Ghebreyesus said, it so far seems to be mostly limited to close family members and health-care workers. There have been no cases of human-to-human transmission outside China so far, but it could happen, he believes.
There will likely be more cases of the virus in China and elsewhere, he said.
Declarations of a public health emergency of international concern are relatively rare.
Only five emergencies have been declared in the past decade: the 2009 H1N1 flu pandemic, an Ebola outbreak in West Africa in 2014, a polio outbreak in 2014, the Zika virus in 2016, and the ongoing Ebola outbreak in the Democratic Republic of Congo.
Emergency declarations lead to a boost of public health measures to contain the spread of the illness, as well as funding for the crisis.
The WHO says it will reconvene its emergency committee in approximately 10 days to examine the virus, or earlier, if the director-general decides it’s necessary.
For now, the organization recommends simple measures to keep yourself safe from this and other respiratory viruses, like frequent hand-washing and covering your mouth and nose when you sneeze.