Madrid – A ship that left Ushuaia (Argentina) for Antarctica in mid-March has been converted into a laboratory to study the COVID-19, from which an astonishing conclusion has already emerged: of the passengers who tested positive for the coronavirus, 81 percent had no symptoms.
This is just one of the conclusions of a study published in the journal Thorax, from the BMJ group, which, according to their authors, demonstrate that the prevalence of “silent infection” and no symptoms from the current coronavirus may be much higher than previously thought.
For Alan Smyth, co-editor-in-chief of the official journal of the British Thoracic Society, the results of this study would have implications for the relaxation of isolation restrictions and highlight the urgent need for accurate global data on the number of infected by COVID-19.
The aforementioned ship left Ushuaia to make a 21-day cruise through Antarctica, taking a route similar to that used by the explorer Ernest Shackleton. The ship, with 128 passengers, including study scientists, and 95 crew, set sail in mid-March after the World Health Organization (WHO) declared COVID-19 as a pandemic.
According to a note from the BMJ, passengers who, in the previous three weeks, had passed through countries where the rates of COVID-19 infection were already high, were not allowed to board, and everyone’s temperature was taken before boarding to the boat.
Hand sanitizing points were abundant on board the ship, especially in the dining room.
The first case of fever was registered on the 8th, which prompted the immediate adoption of infection control measures: confinement of passengers in their cabins, interruption of daily services, apart from the delivery of meals, and use of personal protective equipment for any crew member who is in contact with sick passengers.
As in those days Argentina had closed its borders, the ship set sail for Montevideo (Uruguay), arriving on the 13th; Eight passengers and a crew member finally required medical evacuation to the hospital at this point due to respiratory failure.
On day 20, 217 passengers and crew were tested for coronavirus PCR; more than half (128; 59%) tested positive. Of those who tested positive, 24 (19%) had symptoms, but 108 (81%) did not.
In 10 cases, two passengers who shared a cabin did not obtain the same result, which can be explained by the false negatives caused by the way samples are taken in the nose, which do not always capture all the virus.
The ship had no contact with other people for 28 days after its departure, so it was the equivalent of a hermetically sealed environment.
The researchers, among others from Macquarie University of Sydney, conclude that the prevalence of COVID-19 infection on cruise ships is likely to be “significantly underestimated”, so they advise that passengers be monitored after landing to avoid the possible spread of the virus in the community.
Alan Smyth acknowledges that it is difficult to find a reliable estimate of the number of COVID-19 positive patients without symptoms, but the figure suggested by the WHO is well below that found on the cruise, he concludes.
A high proportion of infected but asymptomatic individuals can mean a much higher percentage of infections than expected in countries that are emerging from isolation, he warns.
Furthermore, according to the scientist, “regardless of whether those infected are immune or not, the results underscore the urgent need for accurate global data on the number of people infected.”
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