About 1,000 Americans were still stuck in the Chinese city at the center of the new coronavirus outbreak Tuesday, many hoping for seats on a U.S. government-chartered flight expected to leave early Wednesday. Anxiety in Wuhan, a quarantined city of 11 million people — and across Asia — was spreading as fast as the deadly virus.

The virus that emerged late last year had killed at least 106 people as of Tuesday, all of them in China. More than 4,500 others have been infected in more than a dozen countries, including five confirmed cases in the United States. More than 100 people in the U.S. were being tested for the disease across 26 states.

Public health officials from the U.S. and China have warned people to expect many more infections. The disease can be transmitted by people who are showing no symptoms, and a top British infectious disease specialist said Monday that the actual number of cases around the world could already be close to 100,000.

China has locked down more than 15 cities, including Wuhan, virtually quarantining a population of more than 50 million people in a bid to stop the spread of the coronavirus. The U.S. and other nations have been screening passengers arriving from China, and by Tuesday some neighboring countries were starting to impose further restrictions. Some Russian provinces said they would close their borders with China entirely.