Seven Grand Princess cruise ship passengers quarantined at Travis Air Force Base in Fairfield— all with no symptoms — tested positive for the coronavirus, The Chronicle has learned, as the first batch of swab results from the voluntary testing came back Friday.

The seven individuals have been sent to a care facility outside Travis for continued care, a federal official familiar with the Travis quarantine and testing told The Chronicle.

The test results raise questions about the quarantine and the fact that two-thirds of the 858 passengers isolated on Travis Air Force Base have declined to be tested, often at the encouragement of federal health officials. The federal official said that the seven positives out of 110 tests would not change the optional testing, including for loved ones who may have been living in quarantine with the infected passengers.

“There is no mandatory testing due to contact with a positive individual,” said the official, whom The Chronicle agreed not to name because this person was not authorized to speak to the media. “There’s no change to the release plan.”

Requests for comment from the U.S. Department of Health and Human Services and Travis Air Base officials were not immediately returned Saturday.

A total of 308 passengers volunteered to be tested earlier this week, but the rest of the results have not returned yet. All of the Travis passengers who had not tested positive or been hospitalized with symptoms while there had staggered release dates, starting Monday and ending Friday.

The large group of passengers was monitored by federal health officials during their stay, getting temperature checks twice a day. Despite Vice President Pence’s vow that all the passengers would be screened for the virus, only a third agreed to the testing. Passengers said administrators dissuaded them, saying the 14-day quarantine was sufficient and a test could potentially delay their release. Others said the testing numbers would have been higher if offered when passengers first arrived at the air base, but there were not enough tests, personnel or protective equipment.

John Swartzberg, a UC Berkeley infectious disease expert, said even with the positive test results of asymptomatic passengers, decisions on releasing them back into the general public are incredibly nuanced.

“If these people were in the quarantine and they did not cross infect each other, then the 14 days of being in quarantine is a reasonable plan,” he said. “It’s not perfect, but nothing is perfect with this.”

There is a “very, very small” chance of getting ill after two weeks, Swartzberg said. He added that studies are showing there are asymptomatic coronavirus carriers and that infected individuals without symptoms can remain contagious.

“Those are big unknowns and it’s impossible to write a policy where somebody gets released and absolutely does not release the virus,” he said. There is also evidence of coronavirus false-negative test results, he said, so even testing is not foolproof.

George Rutherford, a UCSF professor of epidemiology, agreed that the 14-day quarantine should be sufficient — with complete isolation.

“If there was transmission in the quarantine facility, then it’s another story,” Rutherford said.

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That has been a hot topic among passengers who spoke to The Chronicle. Many complained about how logistics were handled after they disembarked from the cruise ship, saying they were put on crowded buses with people removing their masks to eat next to each other.

Photos circulated in those first days of passengers crowded into a lobby and other common areas. One passenger from the Sacramento area told The Chronicle he has repeatedly complained about the lax nature of food deliveries and common areas. For a while, passengers all got coffee from the same spigot, he said.

“I firmly believe this quarantine was handled with great incompetence,” he said in an email with photos of the intermixing. He asked to not be named due to the tense atmosphere on the base among passengers and federal officials. The Chronicle agreed not to identify the federal official or the former passenger in accordance with its policy on the use of anonymous sources.

Rutherford also urged that close contacts of the seven new infected passengers be further scrutinized.

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“I’d insist on testing close contacts (for instance, a spouse that shared the room), but I think I’d let the others go if they were asymptomatic after 14 days,” he said in an email. “It’s a judgment call.”

Matthias Gafni is a San Francisco Chronicle staff writer. Email: matthias.gafni@sfchronicle.com Twitter: @mgafni