BREAKING: The designation marks an escalation of the global response to an outbreak that has sickened more than 8,100 people and killed over 170. It sets in motion a plan for global coordination to stem the spread of the virus, which originated last month in central China.

This is a developing story. It will be updated.

The United States confirmed a sixth U.S. case of the Wuhan coronavirus Thursday, marking the first time the virus has spread from person to person in the United States.

Chinese officials added more than 1,900 new cases of the coronavirus on the same day, as countries stepped up their efforts to evacuate their citizens trapped in Wuhan, at the epicenter of the growing outbreak.

With experts saying a vaccine is still a long way off, more international cases of the illness appeared Thursday. Australia, Vietnam and South Korea all announced new coronavirus infections, while India and the Philippines had their first ones.

The World Health Organization will reconvene its emergency committee Thursday to determine whether the coronavirus outbreak amounts to a public health emergency of international concern, as the total number of people infected in mainland China surpassed those infected with SARS during the 2002-2003 epidemic. Here’s what we know so far:

● Chinese officials say the death toll in the country has reached 171, with more than 8,1oo confirmed cases of infection as of Thursday evening local time — an increase of more than 1,900 from the previous day. (The figures from Beijing include nine cases in the self-governing island of Taiwan.)

● About 100 cases have been recorded outside mainland China, and four other countries have reported person-to-person transmission of the virus.

● Roughly 200 Americans evacuated from Wuhan landed in California on Wednesday, while the United States confirmed its first case where the virus had spread from person to person within the United States.

● Global markets declined sharply Wednesday as investors weighed the spread of the coronavirus.

● Infections also have been confirmed in France, Hong Kong, Japan, Nepal, Cambodia, Singapore, the United Arab Emirates, Vietnam, Taiwan, Canada and Sri Lanka. We’re mapping the spread here.