The World Health Organization (WHO) will hold an urgent meeting this week to decide whether the coronavirus is an international public health emergency.

In a news conference Wednesday morning, WHO Director-General, Dr. Tedros Adhanom Ghebreyesus, said the agency is working closely with public health authorities in affected countries.

For the virus to be labeled an international public health threat by WHO, it must spread locally when it arrives in new parts of the world.

"Although the numbers outside China are still relatively small, they hold the potential for a much larger outbreak," said Tedros, who is known by his first name.

Officials stress there still is a lot they don't know about the virus and that information is changing by the hour.

According to German health officials, a man contracted the coronavirus from a colleague visiting from Shanghai. Officials believe this could be the first case of person-to-person transmission outside of China. Tedros also described other such cases, including in Japan and Vietnam, as worrying, adding that experts will decide on Thursday whether to declare the coronavirus outbreak a global emergency.

The WHO chief also expressed regret for referring to the global risk of the outbreak in three reports last week as "moderate" instead of "high."

The coronavirus includes a range of symptoms and about 20 percent of people become severely sick and develop pneumonia and respiratory failure.

Tedros told reporters he met on Tuesday with Chinese President Xi Jinping, National Health Commission Minister Ma Xiaowei and Foreign Minister Wang Yi to discuss virus containment and sharing information. 

He noted he felt encouraged by President Xi's involvement in the response to the virus.

Tedros also emphasized that China "needs the world's solidarity and support," and that "the world is pulling together to end the outbreak, building on lessons learned from past outbreaks."