The World Health Organization on Thursday declared that the Wuhan coronavirus outbreak was a global health emergency, acknowledging that the disease now represents a risk beyond China, where it emerged last month.
The concern is that it could spread to countries with weaker health systems.
The death toll now stands at 170 people in China.
The WHO said there had been 98 cases in 18 countries outside of the country, but no deaths.
Most cases have emerged in people who have travelled from the Chinese city of Wuhan, where the outbreak began.
However, there have been eight cases of human-to-human infection – in Germany, Japan, Vietnam and the United States.
Dr Tedros, speaking at the press conference in Geneva, described the virus as an “unprecedented outbreak” that has been met with an “unprecedented response”.
He praised the “extraordinary measures” Chinese authorities had taken to prevent it from spreading.
“Let me be clear, this declaration is not a vote of no confidence in China,” he added.
Researchers are racing to develop a vaccine to protect people from the virus. One lab in California has plans for a potential vaccine to enter human trials by June or July.
