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Young, healthy people who contract the coronavirus are often asymptomatic, very rarely need hospital care, and can unintentionally pass the virus to a roommate even by following strict quarantine orders, according to two new studies from the US Navy. The results support the need for strong measures, such as daily testing, that go beyond temperature checks and symptom reporting now commonly deployed to prevent transmission in offices, dorms and other group settings, said the authors.
“These findings all underscore the need for ongoing testing strategies,” said Dr. Andrew Letizia, commander and infectious disease specialist at the Naval Medical Research Center in Silver Spring, Md., And lead author of one of the studies. “We need to increase public health measures and strengthen them with regular testing” in such settings, he said.
The new reports, both published on Wednesday by the New England Journal of Medicine, clarify much of what is known or suspected of the effect of Covid-19 on young adults, while also exposing the limitations of quarantine measures . A study, led by Dr Letizia, detailed the rate of new infections detected among nearly 2,000 recruits quarantined near Parris Island Marine Corps Recruit Depot, South Carolina, over the summer. It was conducted in collaboration with researchers from the Icahn School of Medicine at Mount Sinai in New York.
The other describes an outbreak on the USS Theodore Roosevelt, an aircraft carrier on which nearly a quarter of the crew – more than 1,200 sailors and women – tested positive in the spring.
Many studies carried out over the past year have shown that Covid-19 is often asymptomatic in young people and that the symptoms that appear are usually mild. And reports of epidemics on cruise ships, particularly the Diamond Princess in January and February, had revealed that the virus easily moved through the air between people quarantined together in small rooms.
The two new studies are distinct in that they describe situations in which officials had the resources and authority to promulgate comprehensive measures and, in the case of Navy Command in South Carolina, were carefully prepared from the start. . The 1,848 recruits who volunteered for this study agreed to stay in quarantine for two weeks at home before reporting for work; after their arrival, they entered quarantine for another two weeks, at the Citadel, the military college in Charleston, which the Marine Corps took over for this purpose. They were tested for the virus upon arrival, a week later, and again at two weeks.
Containment measures were extended on the campus. Recruits were instructed to wear masks at all times, except during sleep; stand six feet from others; and to disinfect the toilet after using it. Most had only one roommate, and all training took place outside.
“Yet despite very strict procedures monitored around the clock by marine instructors, we have identified six clusters of transmission,” said Dr Stuart Sealfon, professor of neurology at the Icahn School of Medicine, senior author of the study. These clusters were the result of a recruit infecting a roommate, or several others in the same platoon, which has 50 to 60 members.
The researchers determined that about 1% of the recruits arrived infected with the coronavirus, almost all without knowing it. Another two percent were infected during the quarantine period. By the end of the study, the team had identified 77 recruits with positive tests, each of whom had been transferred to a different dorm, to be quarantined on their own.
The Theodore Roosevelt outbreak, which began in late March and has spread through May, gives a clearer picture of how the virus can invisibly spread among young people. Out of 4,779 crew members, 1,271 eventually tested positive, 77% of whom were asymptomatic at the time. Almost half of those who tested positive, 43%, never showed symptoms of Covid-19; a total of 23 people were hospitalized, four of whom were admitted to intensive care. One is dead.
“It really shows the stealthy nature of the virus and how it can move asymptomatically in such a population,” said Cmdr. Matthew Kasper, the Navy microbiologist who led the study. “And I think the unique situation here – we had everyone tested. It was not based on any subjective senses or memory recall. These are precise numbers.
Outside experts said the two studies, taken together, have demonstrated not only how infectious the virus is, but what measures should ideally be in place to contain it, whether in military or civilian populations.
“Approaches learned from the USS Theodore Roosevelt and Parris Island can be applied, with varying degrees of relevance, to shared terrestrial life situations, “wrote Dr. Nelson Michael, of the Walter Reed Army Institute of Research, in an accompanying editorial,” as the dormitories of university, prisons, and residential care facilities, as well as athletic training environments, meat processing facilities and isolated power plants.
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