The World Health Organization declared the coronavirus outbreak an international public health emergency on Thursday as the number of confirmed cases topped 7,800 globally.

The majority of cases, which have resulted in at least 170 deaths, have been in China where health officials say the virus originated. Additional cases have been reported in 18 other countries, including the U.S., France, Canada, Japan, South Korea, Thailand, India and Australia.

We must all act together now to limit further spread, said WHO Director-General Tedros Adhanom Ghebreyesus in announcing the health declaration. Our greatest concern is for the virus to spread to other countries with weaker assistance and which are ill-prepared to deal with it.