World Health Organization Health Emergencies Program head Michael Ryan Fabrice Coffrini/AFP/Getty Images

As the number of confirmed coronavirus cases continues to rise, the head of the World Health Organization's Health Emergencies Programme Michael Ryan has said, "The whole world needs to be on alert now."

"The whole world needs to take action and be ready for any cases that come, either from the original epicenter or from other epicenters that become established," Ryan told reporters Wednesday.

His comments come as the WHO will reconvene an emergency committee on Thursday to advise the agency on whether the coronavirus outbreak meets the definition of a public health emergency of international concern, the agency announced.

WHO leadership called the committee back together due to the "potential for a much larger outbreak," WHO Director-General Tedros Adhanom Ghebreyesus said.

Ghebreyesus said that, while nearly 99% of cases have occurred in China, cases of person-to-person transmission in a handful of other countries have become a cause for concern.

Last week, the organization said the virus was an emergency in China, but does not yet constitute an international public health emergency.

Still, in daily situation reports, the WHO has listed its risk assessment as "very high in China, high at the regional level and high at the global level."

Ryan said that many countries are taking action at borders and around travel — and one advantage of declaring an emergency is the ability to better coordinate the global response.