The World Health Organization on Thursday reversed itself and declared the spread of the Wuhan coronavirus a global public health emergency, citing the potential of the virus to spread globally.

WHO officially declared the coronavirus, which already killed 171 in China, a “public health emergency of international concern” (PHEIC). The announcement came after criticism of the United Nations health agency’s decision last week not to declare the outbreak a PHEIC, even though the virus was spreading rapidly.

“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,” WHO director general Tedros Adhanom Ghebreyesus said. “The vast majority of cases outside of China have a travel history to Wuhan or contact with someone with a travel history to Wuhan. We don’t know what sort of damage this virus could do if it were to spread to a country with a weaker health system.”

The virus has already spread to more than a dozen countries and the number of cases has risen more than tenfold in a week. There are more 8,000 cases in China now, and the virus has spread to 18 other countries. In the United States, doctors said Thursday that the first human-to-human transmission of the virus had occurred.

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Said Tedros: “This declaration is not a vote of non-confidence in China. On the contrary, WHO continues to have the confidence in China’s capacity to control the outbreak,” the Associated Press reported.

A declaration of a global emergency typically brings greater money and resources, but may also prompt nervous governments to restrict travel and trade to affected countries. The announcement also imposes more disease reporting requirements on countries. In the wake of numerous airlines cancelling flights to China and businesses including Starbucks and McDonald’s temporarily closing hundreds of shops, Tedros said WHO was not recommending limiting travel or trade to China. “There is no reason for measures that unnecessarily interfere with international travel and trade,” he said.

Still, Russia announced it was closing its 2,600-mile border with China, joining Mongolia and North Korea in barring Chinese from crossing into their countries.