Twenty-one passengers on a stranded cruise ship are infected by coronavirus. That number could grow.

Nearly half of the people initially tested aboard a cruise ship being held in waters off San Francisco have been infected with the coronavirus, Vice President Mike Pence said late Friday.

Results for 21 of the 46 people officials tested Thursday came back positive, raising fears that the virus could be spreading widely among the more than 3,500 people aboard the Grand Princess. Pence said those infected include 19 crew members and two passengers.

The vice president said authorities plan to bring the cruise ship to a "non-commercial port" over the weekend, where all passengers and crew will be tested for the disease and quarantined as necessary.

The public health crisis on the ship echoed a similar one from last month, when 700 people aboard another Princess Cruises ship, the Diamond Princess, became infected with the coronavirus while the ship was quarantined for weeks off Yokohama harbor in Japan.

U.S. officials, however, made clear Friday they have no intention of keeping the Grand Princess at sea and in limbo for nearly that long.

Back onshore, the coronavirus continued its march across the nation and the globe Friday, upending economies, stretching government resources and alarming health officials.

At least a half-dozen additional states - including Pennsylvania, Kentucky, South Carolina, Hawaii, Oklahoma and Minnesota - announced suspected cases of the virus, meaning half of all states are now wrestling with the outbreak. New York's numbers doubled to 44. Nationally, 15 people have now died from covid-19, the disease caused by the coronavirus, and the total number of cases eclipsed 250, according to a tally by Johns Hopkins University.

Globally, cases of the coronavirus have now surpassed 100,000, with the trend showing few signs of slowing. Friday prayers were disrupted across the Middle East, as Iran shuttered almost 60,000 mosques.

New cases also surfaced across Europe, and President Emmanuel Macron urged French citizens to stop visiting the elderly.

Pence's announcement at the White House seemed at odds with the wishes of President Donald Trump, who said during a visit Friday afternoon at the Centers for Disease Control and Prevention in Atlanta that he would prefer to keep passengers on the Grand Princess for the moment.

"I don't need to have the [infection] numbers double because of one ship that wasn't our fault, and wasn't the fault of the people on the ship either," he said. "I can live either way with it. I'd rather have the people stay on, personally."

But public health experts say cruise ships are particularly dangerous places during outbreaks because of the combination of close quarters and staff members without the needed training and resources.

"This is probably the least ideal environment to try and quarantine and maintain proper infection prevention measures," said Saskia Popescu, an epidemiologist with Honor Health, a Phoenix hospital system.

The situation with the Grand Princess is particularly fraught because authorities are also racing to track down passengers who took an earlier voyage on the ship last month to Mexico. A 71-year-old man from that trip later died in California from covid-19.

The 3,533 people aboard the Grand Princess - 2,422 guests and 1,111 crew representing 54 nationalities - learned of the test results and the government's plans for the ship only as Pence spoke from the White House.

In a message to passengers, the ship's captain apologized for not breaking the news to them about the positive test results, saying that "we were not given advance notice of this announcement by the U.S. federal government."

The captain said the CDC was discussing individual results with the ship's doctor and that the California Department of Public Health had asked everyone to remain isolated in their rooms, according to a recording provided to The Washington Post. "This is an evolving situation, and we are doing our best to tell you what we know in a timely manner."

Stuart Freedman, a 61-year-old retired high school math teacher stuck on the ship, sounded largely resigned about what lay ahead.

Freedman said he will be glad to get tested so at least he can find out one way or the other about the virus. But he was frustrated by the president's remarks.

"The thing I didn't like is President Trump wants to keep us on this petri dish because he doesn't want his numbers to spike," Freedman said. "He cares more about his numbers than about us."

As they spent Friday waiting for news of tests results and where government officials might send the troubled ship, they found themselves by turns frustrated, bored and apprehensive.

Passengers were given sheets asking about their meal choices. Princess Cruises said in a statement Friday that workers would distribute forms allowing guests to request prescription refills, and the cruise line offered free Internet access and complimentary phone calls. Some played Sudoku. Others played cards.

Kailee Higgins Ott, 17, and her mother, Leann Higgins, feasted on a large breakfast of pancakes, bacon, eggs, pastries, fruit and yogurt. Lunch included pasta, fajitas and cream puffs. They watched "Charlie's Angels."

When she told a fellow passenger she was out of toothpaste - both were out on their balconies - her neighbor offered her an extra tube.

"Everyone's being super nice," Higgins Ott said.

For passenger Kari Kolstoe, the wait meant uncertainty about whether she would get back home to Grand Forks, North Dakota, in time for cancer treatment early next week.

Kolstoe, 60, who said she has Stage 4 neuroendocrine cancer, said it had been "a very difficult winter" and that the cruise was supposed to be a much-needed respite.

"I've been wanting to get away this winter," she said in a telephone interview from her room. Instead, Kolstoe said, she was stuck in her room, cycling among boredom, frustration and angst.

Neither Kolstoe nor her husband have any symptoms or have been tested, she said, adding that she wants to get off the ship before that happens because of her "compromised" situation. "I'm trying to stay positive," she said. "And [I] know that everybody's under a lot of stress."

Wray McClelland, who has been on the ship since Feb. 11 and confined to his room since Wednesday, said he and his wife have been talking, watching TV, playing games and doing whatever possible to pass the time. He said in an email Thursday night that his thoughts were with the crew members who had to work through the uncertainty.

"I cannot imagine," he said. "Fearful of the virus and working so hard and still having contact with us in the form of sheets and dishes while so much is unknown about the virus."

Freedman, the former math teacher, said people on the Grand Princess on Friday remained mostly patient, if anxious, as they tried to make the best of a grim situation.

"People are kind of collegial in a situation like this," he said. "Most people are dealing with it the best they can."

As he sat confined in his room on the sprawling ship, he was mostly sanguine about what might lie ahead as public officials try to defuse the latest calamity fueled by the ever-expanding global outbreak.

"If we get it, hopefully we're going to survive it," he said. "If not, you've got to die of something. That's my attitude."

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The Washington Post’s Lenny Bernstein, William Booth, Amy Goldstein, Jay Greene, Ben Guarino, Alex Horton, James McAuley, Rick Noack, Siobhán O’Grady, Hannah Knowles, Lena H. Sun, Reis Thebault and Scott Wilson contributed to this article.