June 10 (UPI) -- A new study on hundreds of Navy servicemen aboard the USS Theodore Roosevelt aircraft carrier showed that 18.5 percent of those who contracted the coronavirus were asymptomatic, meaning they showed no symptoms of the disease.
The study, conducted by the Navy and the U.S. Centers for Disease Control and Prevention released Tuesday, also reported nearly 60 percent of service members in the sample of 382 sailors tested positive for COVID-19 antibodies, meaning they had been infected with the virus and was "a promising indicator of at least short-term immunity."
It also reported that most who were infected were only "mildly ill" with a loss of taste or smell being the most common symptom. Those who experienced either of these symptoms, the study said, were 10 times more likely to be infected compared to those who did not.
Because many were either mildly ill or showed no symptoms at all, the study states that symptom-based surveillance might not detect all infections.
"This is a stealthy virus and the results from this outbreak investigation provides us with increased knowledge about COVID-19 so we can better protect the crew, their shipmates on other vessels and ultimately the nation," U.S. Navy Surgeon General Rear Adm. Bruce Gillingham said in a statement.
The nuclear-powered aircraft carrier departed Guam on Thursday after docking at the island territory late March to isolate and treat its 5,000 crew after 23 had tested positive for COVID-19.
Controversy surrounded the vessel after a letter from its former captain, Brett Crozier, to Navy brass asking for more resources to fight the coronavirus was published, which led to his removal from the vessel.
Compared to the number of studies on older adults and COVID-19, there has been relatively few on younger, healthy Americans and this investigation improves the understanding of the virus' effects among this population, the study said.
More than 1,000 sailors on the ship tested positive for COVID-19, one of whom died, and the study's investigation occurred over four days in mid-April among those who volunteered to complete questionnaires and provide specimens.
The study found that those who took preventative measures had a lower infection rate compared to those who did not. Only 55.8 percent of those who wore masks fell sick compared to 80.8 percent who didn't and 53.8 percent of those who avoided common areas contracted the virus compared to 67.5 who enjoyed the spaces. In terms of social distancing, those who observed the practice fell sick at 54.7 percent versus 70 percent who did not adopt the behavior.