The World Health Organization has declared the novel coronavirus outbreak a public health emergency of international concern, after an emergency committee reconvened Thursday in Geneva.

Last week, the organization said the virus did not yet constitute the emergency declaration. But with rising numbers and evidence of person-to-person transmission in a handful of cases outside of China, WHO leadership called the committee back together due to the “potential for a much larger outbreak,” WHO Director-General Tedros Adhanom Ghebreyesus told reporters earlier this week.

WHO defines a public health emergency of international concern as “an extraordinary event” that constitutes a “public health risk to other States through the international spread of disease” and “to potentially require a coordinated international response.” Previous emergencies have included Ebola, Zika and H1N1.