21 test positive for coronavirus on California cruise ship, Vice President Mike Pence says

A total of 46 people on the ship were tested with 21 testing positive for the infection, 24 were negative and one was inconclusive, Pence said during a Coronavirus Task Force press briefing.

Of the 21 people who tested positive, 19 were crew members of the ship and two were passengers.

The Grand Princess had been in limbo off the California coast with thousands aboard since Wednesday and the California Air National Guard dropped off test kits by helicopter to the ship on Thursday, when officials learned that a California man who'd traveled on that ship last month contracted coronavirus and died this week.

Passengers on the ship found out about the test results from Pence's press briefing, according to a video from a passenger on the ship.

"We apologize but we were not given advance notice of this announcement by the US federal government," according to an announcement broadcast on the ship and recorded on the video. "It would have been our preference to be the first to make this news available to you."

Pence said Friday he's working with California Gov. Gavin Newsom, the Centers for Disease Control and Prevention and the Department of Health and Human Services to develop a plan for the Grand Princess to return to a "non-commercial port."

"All passengers and crew will be tested for the coronavirus," Pence said. "Those that need to be quarantined will be quarantined. Those that require additional medical attention will receive it."

There are more than 3,500 people aboard the Grand Princess -- 2,422 guests and 1,111 crew members, Princess Cruises said. They represent 54 nationalities.

As of Friday afternoon, California had 56 positive confirmed cases of coronavirus and one death.

A two-week trip is cut short

The Grand Princess was on a two-week trip from San Francisco to Hawaii and was scheduled to return Saturday.

The ship was diverted toward San Francisco on Wednesday -- with a planned stop in Mexico canceled -- after the California man's death in Placer County. His was the first coronavirus fatality outside Washington state in an outbreak that's killed 14 people nationwide.

The man, who hasn't been named publicly, was 71 and had underlying health conditions, Placer County health officials said. He was likely exposed to the virus on a Grand Princess cruise between February 11 and 21 from San Francisco to Mexico.

Shortly after the Grand Princess finished its Mexico trip last month, it started the latest cruise, with some people from the February cruise remaining on the ship for the current cruise.

Some of those identified for testing included several who were on the Mexico voyage with the victim. At least six passengers who disembarked from that February trip tested positive, including the man who died. The latest person to be infected was a Ventura County resident who has been quarantined at home with mild symptoms, according to county officials.

No guests were allowed to disembark until all test results were received, Princess Cruises said in a statement.

The captain advised passengers Thursday night that more people than the initial 45 may be tested on Friday, according to a video clip CNN obtained from inside the ship from passenger Teresa Duncan Johnson.

Though all guests have been asked to stay in their rooms, "we're in discussions with the CDC regarding time for guests to access the open deck for fresh air and exercise," the captain says, referring to the US Centers for Disease Control and Prevention.

A race to trace possible infections

Newsom has declared a state of emergency, saying local health officials are working with their federal counterparts to trace people who had contact with the man who died.

Princess Cruises has shared relevant data with the CDC to help notify state and county health officials, who will follow up with anyone who may have been exposed to coronavirus, cruise line officials said.

"Cruise ships are posing probably one of the biggest challenges that we are seeing in this outbreak," said Dr. Jeanne Marrazzo, infectious diseases director at the University of Alabama at Birmingham.

"We know these cruise ships are essentially ... we've been calling them incubators, they are incredibly very healthy environments for the pathogens that we're talking about."

Another cruise ship was linked to the virus

Another Princess Cruises ship, the Diamond Princess, was the site of a major coronavirus outbreak as it was docked at Yokohama, Japan, last month.

After the first handful of cases were reported from the Diamond Princess, Japanese officials decided to keep people aboard and quarantine the ship. Eventually, more than 700 people aboard became infected with coronavirus.

"The problem with the Diamond (Princess) cruise ship, as we've learned, was that when you quarantine people like that, with a few possible infected people, the likelihood of infecting many more people goes up," CNN Chief Medical Correspondent Dr. Sanjay Gupta said.

A top Japanese government adviser has said the quarantine of the Diamond Princess "may not have been perfect."

Infected crew members may have passed on infections to other crew members or guests, said Dr. Norio Ohmagari, director of the Disease Control and Prevention Center at Japan's National Center for Global Health and Medicine.

It's impossible to fully isolate staff members during a cruise ship quarantine, other said.

"Unfortunately, to maintain daily life of the more than 3,700 passenger cruise, we needed help, we needed support from cruise members to maintain the daily life," said Yosuke Kita of Japan's Ministry of Health, Labor and Welfare.

US infection cases are going up

Health officials are urging local communities to consider ways to stop the coronavirus from spreading as the number of infections soared to at least 282 nationwide.

That number includes at least 46 former passengers of the Diamond Princess cruise ship.

Besides the former Grand Princess passenger in California, 14 people have died in Washington state -- including many who are linked to a long-term nursing home near Seattle.