The World Health Organization declared on Thursday that the Wuhan coronavirus outbreak was a global health emergency, acknowledging that the disease now represents a risk beyond China, where it emerged last month.
The decision reversed the organization’s decision just a week ago to hold off such a declaration.
Since then, W.H.O. officials said, thousands of new cases in China and clear human-to-human transmission in several other countries— now including the United States — warranted a reconsideration of that decision by the agency’s expert committee.
The W.H.O.’s declaration — officially called a “public health emergency of international concern” — does not have the force of law. But it serves notice to all United Nations member states that the world’s top health advisory body thinks the situation is grave.
Governments then make their own decisions about whether to close their borders, cancel flights, screen people arriving at airports or take other protective measures.
