BEIJING — As new cases of the coronavirus spiked on two continents, the World Health Organization warned on Monday that the world was not ready for a major outbreak, even as it praised China’s aggressive efforts to wrest the epidemic under control.

After two weeks on the ground in China, a team sent by the W.H.O. concluded that the draconian measures China imposed a month ago may have saved hundreds of thousands of people from infection. Such measures — sealing off cities, shutting down businesses and schools, ordering people to remain indoors — have provoked anger in China and could be difficult to replicate in democratic countries with a greater emphasis on protecting civil liberties.

“There’s no question that China’s bold approach to the rapid spread of this new respiratory pathogen has changed the course of what was a rapidly escalating and continues to be a deadly epidemic,” said Bruce Aylward, a Canadian doctor and epidemiologist who has overseen international campaigns to fight Ebola and polio and who led the W.H.O. delegation.

The epidemic has already killed more than 2,600 people in China, mostly in Hubei Province, where the outbreak began in December, and infected more than 77,000 people. But the number of new infections in China has been steadily dropping, giving officials in the country confidence that the extraordinary measures have been effective in blunting the virus’s spread.