21 people on Grand Princess cruise ship held off California coast test positive for coronavirus

A helicopter dropped coronavirus test kits onto the Grand Princess cruise ship which is idling off the coast of San Francisco, Thursday, March 5, 2020. (Bill Pearce via The New York Times) -- NO SALES; FOR EDITORIAL USE ONLY WITH NYT STORY CALIF-VIRUS-CRUISE BY TIM ARANGO, SARAH MERVOSH AND JENNY GROSS FOR MARCH 5, 2020. ALL OTHER USE PROHIBITED. -- less A helicopter dropped coronavirus test kits onto the Grand Princess cruise ship which is idling off the coast of San Francisco, Thursday, March 5, 2020. (Bill Pearce via The New York Times) -- NO SALES; FOR ... more Photo: BIll PIERCE / NYT Photo: BIll PIERCE / NYT Image 1 of / 12 Caption Close 21 people on Grand Princess cruise ship held off California coast test positive for coronavirus 1 / 12 Back to Gallery

Vice President Mike Pence said in a Friday press conference that 21 people on the Grand Princess cruise ship being held off the California coast tested positive for coronavirus, including 19 crew members and two passengers.

"Working in close consultation with Governor Gavin Newsom and the State of California, we have developed a process for addressing our findings and resolving the circumstances facing Americans and people from around the world and the crew on the Grand Princess," Pence said.

Among the 3,500 people on the ship, 46 people were swabbed Thursday and test results arrived Friday. 21 tested positive for the coronavirus, 24 tested negative, and one test was inconclusive. Pence said the plan is to now test everyone on the ship and quarantine or treat as needed.

Federal officials have been working with the state and “we have developed a plan to bring the ship to a non-commercial port," Pence said. “All passengers and crew will be tested for the virus. Those that will need to be quarantined will be quarantined. Those who will require medical help will receive it.”

Confined to their cabins, passengers aboard a mammoth cruise ship off the California coast awaited coronavirus test results Friday amid evidence the vessel was the breeding ground for a deadly cluster of at least 10 cases during its previous voyage.

On Thursday, a California Air National Guard helicopter crew lowered test kits onto the 951-foot Grand Princess by rope and later retrieved them for analysis as the vessel waited off San Francisco, under orders to keep its distance from shore.

“The ship will not come on shore until we appropriately assess the passengers,” California Gov. Gavin Newsom said Thursday.

Health officials trying to establish whether the virus is circulating on the Grand Princess undertook the testing after reporting that a passenger on a previous voyage of the same ship, February 11 to 21, died of the disease.

In the past few days, health authorities disclosed that at least nine other people who were on the same journey were also found to be infected. And some passengers on that trip stayed aboard for the current voyage.

While the risk to Americans in general remains low, "if you are an individual with a serious health condition or are elderly, it is important to take precautions and use commons sense," Pence said, adding "cruise ships present a unique challenge for health officials and so we would ask elderly Americans to use common sense and caution in planning and cruise ship travel in the future."

Another Princess cruise ship, the Diamond Princess, was quarantined for two weeks in Yokohama, Japan, last month because of the virus, and ultimately about 700 of the 3,700 people aboard became infected in what experts pronounced a public-health failure, with the vessel essentially becoming a floating germ factory.

An epidemiologist who studies the spread of virus particles said the recirculated air from a cruise ship’s ventilation system, plus the close quarters and communal settings, make passengers vulnerable to infectious diseases.

“They’re not designed as quarantine facilities, to put it mildly,” said Don Milton of the University of Maryland. “You’re going to amplify the infection by keeping people on the boat.”

He said the fallout from the ship quarantined in Japan demonstrates the urgent need to move people off the ship.

“My advice is to get people off and into a safer quarantine environment than a cruise ship,” Milton said.

The Associated Press contributed to this story.

Amy Graff is a digital editor for SFGATE. Email her news tips at agraff@sfgate.com.

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