– Countries, cities and businesses across the globe issued new travel warnings Tuesday, vastly expanding a cordon intended to control the flow of people to and from China, where the authorities are struggling to contain the outbreak of the new coronavirus.

In the most drastic measure to limit travel, the Hong Kong authorities reduced by half the number of flights and shut down rail service to mainland China, and they also limited visas — moves that could inspire other governments to follow suit.

Measures to contain the outbreak of the virus to its epicenter in Hubei province appear to have failed to stop the contagion.

On Wednesday morning, Chinese officials said the number of cases had increased by nearly a third overnight. Experts warned that the actual number of cases could be significantly higher and growing quickly. The number of deaths attributed to the virus also continued to grow.

Also, an airplane evacuating as many as 240 Americans from a Chinese city at the center of a virus outbreak departed Wednesday before dawn, and was en route to the U.S., a U.S. State Department official said.

The U.S. government chartered the plane to fly out diplomats from the U.S. Consulate in Wuhan and other U.S. citizens. The plane will make a refueling stop in Alaska before flying on to Ontario, Calif., the U.S. Embassy in China has said.

When the plane arrives in Anchorage, Ala., passengers will clear customs and go through the Centers for Disease Control screening.

"Then they will put them back on the plane and then send them on to their final destination," said Jim Szczesniak, manager of the Ted Stevens Anchorage International Airport. He didn't know how long it would take beyond "hours."

The new travel restrictions put a deeper freeze on China's contact with the world, cutting off business and tourism as China's economy faces a potential slowdown.

With China's Lunar New Year holiday nearing its end, companies ordered workers to stay home and avoid travel. The economic effect of such measures pointed to a deeper political crisis, with many people accusing the Chinese authorities online of failing to act quickly to contain the virus, even as the government continues to struggle to control its spread.

The travel advisories and bans came as the virus showed early signs of spreading outside China, with cases of transmission to people who had not recently traveled to China reported in Japan, Germany and Vietnam. Countries across the world may now be faced with the task of limiting the spread of the disease on their own soil, not simply seeking to identify and quarantine infected people who had been in China.

Officials at the U.S. Centers for Disease Control and Prevention warned against nonessential travel to China, noting that there is "limited access to adequate medical care in affected areas."

The World Health Organization revised its global risk assessment for the outbreak from "moderate" to "high," although it noted this shift in a footnote buried in a report published Monday. The change in the risk assessment, which coincided with a visit to China by the organization's director general, risked confusing the public about the severity of the outbreak, which has killed more than 130 people in China and been diagnosed in at least 14 countries.

Chinese officials said Wednesday that 132 people had died from the virus, up from 106 the day before. The total number of confirmed cases rose sharply as well, to nearly 6,000 on Wednesday, according to the National Health Commission.

Businesses that operate in China have issued warnings of their own. In a flurry of e-mails sent in recent days, General Motors, Honeywell, Bloomberg, Facebook and other companies have warned employees not to travel within mainland China.

Honeywell, which has offices and operations across China, said it had restricted travel to some regions but did not specify which ones. A spokesman for General Motors said the company had issued a global travel ban to China, with only "business-critical" travel allowed and only after clearance from a doctor.

The Associated Press contributed to this report.