The United States reported its first case of person-to-person transmission. Experts say cases of person-to-person transmission – which have also been detected outside China in Germany, Vietnam, and Japan – are especially concerning because they suggest greater potential for the virus to spread further.

Tedros Adhanom Ghebreyesus, WHO director-general, told a news conference in Geneva that recent weeks have witnessed an unprecedented outbreak which has been met by an unprecedented response.

“Let me be clear, this declaration is not a vote of no confidence in China,” he said. “Our greatest concern is the potential for the virus to spread to countries with weaker health systems.”

The declaration of a global emergency triggers recommendations to all countries. It is aimed at preventing or reducing cross-border spread of disease.

Tedros said the WHO was not recommending limiting trade or travel to China due to the outbreak, however.

The vast majority of the more than 7,800 cases detected globally, according to the latest WHO data, have been in China, where the virus originated in an illegal wildlife market in the city of Wuhan.

But nearly 100 cases have emerged in other countries, spurring cuts to travel, outbreaks of anti-China sentiment in some places and a surge in demand for protective face masks.

Officials from the U.S. Centers for Disease Control and Prevention said the flu-like virus was confirmed in a man in Illinois, bringing the total number of U.S. cases to six. The man’s wife, who was also infected, had previously travelled to China, but he had not.

The WHO held off twice last week from declaring a global emergency. Thursday’s move will trigger tighter containment and information-sharing guidelines, but may disappoint Beijing, which had expressed confidence it can beat the “devil” virus.

Jeremy Farrar, director of the Wellcome Trust, said the WHO decision was “absolutely right”.

“Declaration of an international emergency will undoubtedly sharpen governments’ focus on protecting citizens,” Farrar said. The needed public health measures would be a “challenge” for all countries, but would be especially difficult for lower-income countries, he added.

The virus has spread quickly since the WHO’s Emergency Committee last met a week ago. But there has been no death reported outside China and neither has the virus emerged in Africa.

“The vast majority of cases outside China have a history of travel to Wuhan or history of contact with someone with a travel history to Wuhan,” said Teros.

The total number of infections has already surpassed the total in the 2002-2003 Severe Acute Respiratory Syndrome (SARS) epidemic.

SARS also came from China, killing about 800 people and costing the global economy an estimated $33 billion.

Economists fear the impact could be bigger this time as China now accounts for a larger share of the world economy. Markets have been spooked since news of the virus emerged earlier this month.

Companies have also been rattled and Alphabet Inc’s Google and Sweden’s IKEA were the latest big names to close China operations. South Korea’s Samsung Electronics Co Ltd extended its Lunar New Year holiday closure for some Chinese production facilities.

Airlines to suspend flights to mainland China include Air France, Lufthansa, Air Canada, American Airlines and British Airways.

Thousands of factory workers currently on Lunar New Year holidays may struggle to get back to work next week due to travel restrictions.

China dominated U.S. Federal Reserve Chair Jerome Powell’s news conference on Wednesday. “When China’s economy slows down we do feel that,” he said.

REUTERS