In a paper published in the journal Thorax, a team of Australia researchers described the first instance of complete COVID-19 testing of all passengers and crew on an isolated cruise ship during the current pandemic: of the 217 passengers and crew on board, 128 tested positive for COVID-19 on reverse transcription-PCR; of the COVID-19-positive patients, only 24 (19%) were symptomatic.
The majority of COVID-19-positive patients may be asymptomatic. Image credit: NIAID.
Macquarie University’s Dr. Alvin Ing, Dr. Christine Cocks of Sunshine Coast University Hospital, and Dr. Jeffery Peter Green from Royal Australian College of General Practitioners described events on an expedition cruise ship carrying 128 passengers and 95 crew members.
The ship departed from Ushuaia, Argentina, for a planned 21 day cruise of the Antarctic, taking a similar route to that of Ernest Shackleton in 1915-17.
It set sail in mid-March after the World Health Organization had declared COVID-19 a global pandemic.
Passengers who, in the previous three weeks, had passed through countries where COVID-19 infection rates were already high, were not allowed to board. And everyone’s temperature was taken before embarkation.
Hand sanitizing stations were plentiful aboard ship, particularly in the dining room.
The first case of fever was reported on day 8, prompting the immediate adoption of infection control measures.
This included confining passengers to their cabins, stopping daily servicing, apart from the delivery of meals, and the wearing of personal protective equipment for any crew member in contact with sick passengers.
As Argentina had closed its borders, the ship sailed to Montevideo, Uruguay, arriving on day 13.
Eight passengers and crew eventually required medical evacuation to hospital at this point for respiratory failure.
On day 20, all the remaining 217 passengers and crew were swab tested for coronavirus; 128 (59%) tested positive.
Original and subsequent route of cruise ship. Image credit: Ing et al, doi: 10.1136/thoraxjnl-2020-215091.
“In 10 instances, two passengers sharing the same cabin didn’t have the same test result, possibly because the current swab test returns a substantial number of false negative results,” the researchers said.
Of those testing positive, 24 (19%) had symptoms, but 108 (81%) didn’t.
The ship had no contact with other people for 28 days after its departure, so was the equivalent of a hermetically sealed environment.
“The prevalence of COVID-19 infection on cruise ships is likely to be significantly underestimated,” the scientists said.
“We recommend that passengers should be monitored after disembarkation to ward off potential community spread of the virus.”
“And the potentially high rate of false negative results obtained with the current swab tests suggests that secondary testing is warranted.”
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A.J. Ing et al. COVID-19: in the footsteps of Ernest Shackleton. Thorax, published online May 27, 2020; doi: 10.1136/thoraxjnl-2020-215091
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