The number of people infected with the new coronavirus but have no symptoms was found to be much higher than expected, according to a new cruise ship study.
The study, published Saturday in the journal Thorax, found that more than 80% of those who tested positive for COVID-19 had no symptoms.
The journal’s editor-in-chief Alan Smyth said the findings could be important as lockdown restrictions started to ease in some nations, including the United States. He said the findings also highlight the need for accurate data on how many people have been infected globally.
The cruise ship study looked at 128 passengers and 95 crew members that left Argentina in mid-March for a 21-day cruise of the Antarctic. The voyage began after the WHO had declared COVID-19 a global pandemic.
The cruise did not allow passengers who had been from nations where the infection rate was higher. Every passenger who was allowed to board the ship had their temperature checked, with numerous hand sanitizing stations.
The first case on the ship was reported on the eighth day of the voyage, with immediate implementation of infection control measures. Crew members were provided personal protective equipment (PPE) and passengers were confined to their cabins.
On day 13, the ship arrived in Uruguay, where eight passengers and crew members required medical evacuation to hospital for respiratory failure related to COVID.
On day 20, the remaining 217 passengers and crew members underwent the COVID test, and more than half of them tested positive. However, it was found that more than 80 percent of those who tested positive were asymptomatic.
The study researchers said these findings suggest that COVID infection rates on cruise ships are likely to be “significantly underestimated,” and passengers should be screened after leaving the ships to reduce the risk of spread.
They also said that the high rate of false-negative results obtained through current swab tests suggests the need for secondary testing.
Smyth said, “It is difficult to find a reliable estimate of the number of COVID-positive patients who have no symptoms.” “As countries progress out of lockdown, a high proportion of infected, but asymptomatic, individuals may mean that a much higher percentage of the population than expected may have been infected with COVID,” he noted.
