番茄社区

Currently docked and under quarantine in Yokohama, Japan, the Diamond Princess cruise ship carries about 3,700 passengers and crew and, at last count, 218 cases of this novel coronavirus, including a number of infected Americans.

As Ron Klain, JD, who oversaw the U.S. Ebola response in 2014-2015, put it at a recent panel: this cruise ship has become the "country" with the world's second largest number of coronavirus cases after China.

while the ship remains in quarantine, including one case involving a quarantine officer. This ship has captured worldwide attention, with its passengers scheduled to remain under quarantine on the ship until Feb. 19 -- , in which case they are taken to area hospitals.

Worries about coronavirus even extended to cruise ships without known coronavirus cases on board, such as Holland America's MS Westerdam after being turned away by several countries. The World Health Organization (WHO) had to get involved, reminding all countries about the "free pratique" principle, a ship's right to enter port after assurances from the captain that it's free of contagious disease.

So, what about cruise ships makes them an infection control nightmare? Stephen Morse, PhD, of Columbia University Mailman School of Public Health in New York City, summed it up in a sentence: "Transmission dynamics tend to be much more intense," he told 番茄社区.

Public areas of a cruise ship, such as theaters and dining areas where multiple people "congregate informally," make the possibility for transmission much greater, especially for an illness that could be transmitted via the respiratory route, like this novel coronavirus, he said.

Theoretically, quarantining people to their rooms should help with infection control, but Morse noted that people in the inner cabins of a cruise ship, lacking windows or balconies, have no access to fresh air.

"People have speculated if this virus does spread through the respiratory route, it could spread through the HVAC [heating, ventilation, and air conditioning] system," Morse said. "In theory, if you have a HVAC system that picks up air somewhere upstream and carries it downstream and you don't have HEPA [high-efficiency particulate air] filters, which would filter out particles well ... it's not out of the question."

Reports that the rooms have not been cleaned while the passengers are in quarantine might sound unhygienic at first, but in terms of infection control, it's probably "the lesser of two evils."

"When people are coming in to clean, they could get infected themselves. It's better that they not change the linens until absolutely necessary because that risks spreading the infection," Morse said.

Even the meal delivery system can help to reduce risk -- for example, if the meals are being left outside the rooms on trays for the passengers to collect, as opposed to the "face-to-face contact" of their food being handed to them, he added.

Beyond infection control, public health interventions, such as masks, can be more difficult to implement correctly than they appear.

"Most people don't wear [masks] correctly, and they can be counterproductive if they get contaminated. If they don't fit properly, it gives a false sense of security," he said. "N95 respirators [for the crew] require a proper fit, and they're harder to breathe through than regular masks."

Morse also questioned procedures for identifying cases on the Diamond Princess -- temperature scans and health questionnaires to the passengers still on board -- instead of performing virologic testing with nasal swabs more frequently.

"We know people do not show overt signs of illness, don't have increased temperature, or just have GI symptoms. That won't be picked up on temperature scans and questionnaires," he said. "A well-resourced country [like Japan] has the capacity to swab 3,000 people ... a couple times a week, and then test the swabs. It would not be that difficult."

He also noted that if people were tested more frequently, it could be helpful in trying to figure out "if there are some places on the ship that are safer than others," so the crew would know what precautions to take.

In addition, more frequent testing could potentially enable those with multiple negative tests to leave the ship.

"If you test every few days, you have a good idea of who's infected, and then you can remove them before more people get infected. Hopefully [the cases] would level off," Morse said.

As it is, however, on the vessel, Japan Times reported.

So, are the new cases in already infected people who weren't yet showing symptoms or people catching it on the ship? Morse said, "we can't answer that question unless we had some data."

But by keeping everyone on the ship, it's possible that the virus "is dynamic and could keep going around," regardless of infection control procedures, he said.

In the future, testing and determining the airflow pattern on a ship, as well as having high-efficiency air filters, can go a long way towards infection prevention, especially for respiratory illnesses like this novel coronavirus, Morse noted.

"In the air-handling system, you figure out which way the air is flowing, and then you can use that information to prevent infections along the entire line of respiratory exposures," he said.

For advising passengers, Morse emphasized "assiduous handwashing," and pointed out that any 63% ethanol gel, such as Purell, will kill most coronaviruses.

"Most solvents and many sanitizers and disinfectants we use will do a pretty good job on coronaviruses if used properly," he noted.

And while the tale of this particular cruise ship is frightening, it does not mean all leisure travel should be avoided during the outbreak, said Nancy Messonnier, MD, director of CDC's National Center for Immunization and Respiratory Diseases and the agency's point person on containment efforts.

"My parents called because one of their friends is going overseas on a plane and they said should I tell our friends not to fly and I said 'of course not,'" she told 番茄社区. "The same with people going on general cruises: there's no reason to change behavior right now. If we had a reason for people to stop doing those things, we would say it."

Washington Correspondent Shannon Firth contributed to this report.

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