The World Health Organization has declared novel coronavirus a global public health emergency Thursday, a move that will help ramp up resources to combat the virus’ spread.

This decision now sets into motion a chain reaction to help countries build capacity to screen, identify and report cases as novel coronavirus spreads.

“The main reason for this declaration is not for what is happening in China but because of what is happening in other countries,” WHO Director-General Tedros Adhanom Ghebreyesus said. “Our greatest concern is for the potential for the virus to spread to countries with weaker health systems, which are ill prepared to deal with it.”

This news comes after 170 people have died in China, and with more than 7,700 more people sick with confirmed cases, the WHO reported Thursday.

The first case of human-to-human infection was reported in the U.S., the Centers for Disease Control and Prevention said earlier Thursday. This is the world’s eighth instance of human-to-human spread outside of China. Other nations include Germany, Japan and Vietnam.

Physicians diagnosed a man, a Chicago resident in his 60s, with a confirmed case of the virus and said the illness spread from his wife, the second known confirmed case in the U.S. The woman, also in her 60s, had returned from the virus’ point of origin in Wuhan, China, on Jan. 13, and was later diagnosed with novel coronavirus. Her husband did not travel to China.

Worldwide, there are more than 7,800 confirmed cases in 22 countries, including China and the U.S., according to the Centers for Disease Control and Prevention.

The WHO’s decision was warranted to declare a public health emergency of international concern, said Lawrence Gostin, global health law professor at Georgetown University who also directs the World Health Organization Collaborating Center on National & Global Health Law. Already, the virus has met the WHO’s criteria for making such a declaration, he said.

The virus poses serious public health implications, has spread to at least four continents and has influenced travel, Gostin said, meeting the treaty terms under which such declarations are made.

“There’s reasonable probability that we won’t be able to contain this virus in the foreseeable future,” Gostin said.

To prevent further spread of the virus, China halted transportation for more than a dozen cities, including Wuhan, effectively placing more than 50 million people under quarantine. Such an act “is unprecedented in the history of the world,” Gostin said.

Rather than assuming tactics that are backed by evidence, he urged public health officials, especially in China, to go door-to-door with community mobile health clinics to test, treat and isolate infected people, if necessary. The public health community also should develop and maintain contact lists for people who have been exposed to the virus.

In an opinion piece that published in the journal JAMA Thursday, Gostin and his fellow authors wrote that, “It is better to act decisively now rather than wait to see how the outbreak unfolds globally.”