The World Health Organization declared the outbreak of the coronavirus a "public health emergency of international concern" as the disease has now infected more than 7,800 people.
WHO Director-General Tedros Ghebreyesus praised the Chinese government’s response to the outbreak.
He said the outbreak could have been much worse without the Chinese government's intervention.
Nonetheless, the fact that 98 cases have been confirmed in 18 countries outside China necessitated Thursday’s declaration.
“So far we have not seen any deaths outside China, for which we must all be grateful," he said.
"Although these numbers are still relatively small compared to the number of cases in China, we must all act together now to limit further spread.”
Ghebreyesus said that most of the infected people outside China have traveled to Wuhan, China, the suspected epicenter of the disease.
"Our greatest concern is the potential for the virus to spread to countries with weaker health systems, and which are ill-prepared to deal with" it, he said.
The U.S. Centers for Disease Control confirmed Thursday the first U.S. case of human-to- human transmission of the virus.
The coronavirus has now officially passed the SARS epidemic in 2003 in how many people were infected with the disease. The coronavirus has turned out, however, to be much less deadly than SARS.
About one in 10 SARS victims died from the disease, while the mortality rate for coronavirus has been much lower.
U.S. stocks fell Thursday as investors weighed the virus's potential toll on the global economy.