Resident wear masks to buy vegetables in the market on January 23th, 2020 in Wuhan, China. Getty Images, CNBC

World Health Organization has declared Coronavirus a global emergency by the as the outbreak continues to spread outside China.

“The main reason for this declaration is not what is happening in China but what is happening in other countries,” said WHO chief Tedros Adhanom Ghebreyesus.

The concern is that it could spread to countries with weaker health systems.

The death toll is now at 170 in China, while thousands have been infected.

The WHO said there had been 98 cases in 18 countries outside of China, but no deaths.

There have been eight cases of human-to-human infection in Germany, Japan, Vietnam and the United States.

Dr Ghebreyesus, speaking at the press conference in Geneva, described coronavirus as an “unprecedented outbreak” that has been met with an “unprecedented response”.

He praised China’s “extraordinary measures” taken to prevent it from spreading.