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A new study has revealed that more than 80 percent of passengers and crew members on a cruise ship that contracted COVID-19 were asymptomatic.
The research, published in the scientific journal Thorax, notes that 128 of 217 passengers and crew members tested positive for the disease caused by SARS-CoV-2. Of those, 81 percent did not show symptoms, leading researchers to conclude "the prevalence of COVID-19 on affected cruise ships is likely to be significantly underestimated."
"It is difficult to find a reliable estimate of the number of COVID positive patients who have no symptoms," Alan Smyth, the editor-in-chief of Thorax and professor at the University of Nottingham said in a statement.
Smyth added the findings have implications for easing lockdown restrictions around the globe, given the possibility more people may have been infected with COVID-19 than previously believed.
"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 explained.
The cruise involved in the study was a 21-day voyage around the Antarctic, similar to the journey that explorer Ernest Shackleton went on prior to his death. The first fever was on the eighth day of the trip and isolation protocols started immediately, with all passengers confined to their cabins and everyone was issued surgical masks. Personal protective equipment was also worn by anyone who came in contact with passengers.
"Further fevers were detected in three crew on day 10, two passengers and one crew on day 11, and three passengers on day 12," the researchers added.
It's unclear what a higher rate of infection in the general population means. A recent analysis from the Centers for Disease Control and Prevention estimated that more than one-third of COVID-19 patients may not show any symptoms.
A study out of Singapore suggests that COVID-19 patients are not infectious 11 days after getting sick. The researchers noted that a separate study out of Germany found "the degree of viral shedding was very high in the first week of symptoms," supporting their findings.
A separate study from the Korean CDC appears to suggest that patients who test positive for COVID-19 after having previously recovered are not capable of transmitting the infection.
As of Thursday morning, more than 5.7 million coronavirus cases have been diagnosed worldwide, more than 1.69 million of which are in the U.S., the most impacted country on the planet.