The prevalence of symptomless COVID-19 infection may be much higher than previously thought, reveals a study charting the enforced isolation of cruise ship passengers during the current pandemic.
More than eight out of 10 passengers and crew who tested positive for SARS-CoV-2 had no symptoms, according to the study, which is published in the journal Thorax.
The researchers, all of whom were on board the vessel, describe events on on the ship carrying 128 passengers and 95 crew.
The ship departed from Argentina for a planned 21-day cruise of the Antarctic. It set sail in mid-March.
The first case of fever was reported on day 8, prompting the immediate adoption of infection control measures. As Argentina had closed its borders, the ship sailed to Uruguay, arriving on day 13, when eight passengers and crew required medical evacuation.
On day 20 all the remaining 217 passengers and crew were swabbed for SARS-CoV-2. More than half (59%) tested positive. Of these, 24 (19%) had symptoms but 108 (81%) did not.
In 10 instances, two passengers sharing the same cabin had different test results, possibly because of a substantial number of false negatives, say the authors.