COVID-19: Why are cruise ship passengers quarantined and not self-isolated at home?

Canadian passengers of theGrand Princesscruise ship are being sent to Canadian Forces BaseTrenton for a two-week quarantine, while other possibly infected Canadians returningfrom affected countriesare able to self-isolate at home.

The two different courses of actionmay seem inconsistent and raise questions about why the passengerscan'tjust go home,isolate themselvesand, if infected, recover there.

Isaac Bogoch, an infectious disease physician at Toronto General Hospital, saidhe doesn't know why there are two different policies.

"My opinion would be as long as [the passengers are]isolated and adhering to their 14 days, that sounds reasonable to me," he said.

"Whether they're at Trenton or at home, personally, I feel is up for debate," Bogoch said. "I would not let someone off of a cruise shipgo unmonitored for 14 days because there is a real potential that they could get this infection, then transmit it, even unknowingly."

But Colin Lee,a specialist in public health and infectious disease, said the on-base quarantine is a better option from a public health perspective, because compliance is total.

'Reliability is close to 100 per cent'

"Being in Trenton, the reliability is close to 100 per cent. Being quarantined at home is certainly a few notches less than 100 per cent."

So far, two passengers and 19 crew members of theGrand Princess have tested positive for the novel coronavirus.The ship, with more than 3,500 people aboard, hadbeen idling off the coast of San Francisco for several days now, waiting for clearance to dock.

A cruise ship is a closed environment, with very tight quarters and lots of surfaces that potentially have been handled by people with the virus, making it an area where infection is high-risk, said Lee.

"Someone who comes from the ship who is feeling wellisreally in a high-risk situation of having beeninfected."

The Canadiangovernment announced on Sunday that237 Canadians were among those on board the Grand Princess. On Tuesday, Foreign Affairs Minister Franois-Philippe Champagnesaid 228 people were on the flight to CFB Trenton, where they will undergo a 14-day quarantine. He said a "limited number" of people who had other medical conditions that are not related to COVID-19 stayed behind to be treated in California.

Other Canadianswho have been travelling abroad anddeveloped symptoms have been allowed to go home to self-isolation.

Asked about the two policies, the Public Health Agency of Canada said in an email to CBC News thattravellers who have been in an area with a high concentration of cases, like a cruise ship,are at greater risk of having been exposed than travellers coming from an affected area with limited or no exposure to an infected individual.

WATCH | Why viruses spread so quickly on cruise ships:

Why viruses spread so quickly on cruise ships

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Among the reasons viruses, like coronavirus, spread quickly and widely on cruise ships thousands of people in close quarters.

"Imposing these temporary limits on the movements of these Canadians is an extraordinary measure being taken to protect the health of travellers as well as the health of all Canadians," PHAC said.

The majority of COVID-19 cases in Ontario have been mild and have not required hospitalization nor required acute care treatment,David Jensen, a spokespersonwith Ontario's Ministry of Health, said in an email to CBC News.

Self-isolation at home has been recommended for mildly ill cases to ensure hospitals can maintain the capacity to treat and manage more severe casesif required, he said.

For travellers who come back from affected countries andthen develop symptoms, putting them in a more strict quarantine outside of their home would be difficult, Lee said.

"How are you going to transport them? How are you going to get the staff to monitor them? Where are you going to find a space to do that?It just is not feasible."

"We are at the stage now where there are hundreds of people being tested across the country. And they have come from areas of concern and are symptomatic. There's just no feasible way of isolating them anywhere but their home."

It's a different scenario with people on a ship, he said, where there's a "captive audience" and "a bunch of contacts together."

Heeding the calls of public health

Lee said he believes Canadians are heeding the calls of public health officials.

"We have not really seen evidence of a lot of people saying to public health, 'Fine, we're getting tested. But I'm going to ignore your advice,'"he said. "I think people really understand the gravity of the situation, why we're doing this."

Local public health units will regularly check in with confirmed cases to ensure they are abiding by guidance around self-isolation, Jensen said.

As well, medical officers of health have statutory powers they can use to enforce self-isolation if there is a belief that cases are not adhering to guidance.

"As everyone has co-operated, these powers have not been necessary so far," he said.

But it's largely based on an honour system, Bogoch said.

"When people are in home isolation, you're really relying on their good will," Bogoch said. "When people are in quarantine, you're not relying on their goodwill. They're in quarantine. They can't go anywhere."