Young, healthy people who become infected with the coronavirus are often asymptomatic, very rarely require hospital care, and can inadvertently transmit the virus to a roommate under strict new quarantine instructions, two new studies by the U.S. Navy show. The results support the need for rigorous measures such as daily testing, beyond today's temperature checks and symptom reports, to prevent transmission in offices, dormitories, and other group settings, the authors said.
"These results all indicate the need for ongoing testing strategies," said Dr. Andrew Letizia, commandant 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 step up public health action and reinforce it through regular testing," he said in such situations.
The new reports, both published Wednesday by the New England Journal of Medicine, clear up much of what is known or suspected about the effects of Covid-19 on young adults, while also exposing the limits of quarantine measures. In one of Dr. Letizia-led study detailed the rate of new infections recorded in nearly 2,000 quarantined recruits near the Marine Corps Recruiting Center on Parris Island, South Carolina, during the summer. It was carried out in collaboration with researchers from the Icahn School of Medicine at Mount Sinai in New York.
The other described an outbreak in the United States. Theodore Roosevelt, an aircraft carrier on which nearly a quarter of the crew – more than 1,200 sailors – tested positive in the spring.
Numerous studies in the past year have documented that Covid-19 is often asymptomatic in young people and that the symptoms that occur are usually mild. And reports of outbreaks on cruise lines, particularly on the Diamond Princess in January and February, had found that the virus moved easily through the air between people quarantined in small rooms.
The two new studies differ in that they describe situations where officials had the resources and authority to take extensive action and, in the case of the South Carolina Naval Command, were thoroughly prepared from the start. The 1,848 recruits who volunteered for this study agreed to stay at home in quarantine for two weeks before reporting on duty. After arriving, they went into quarantine for two more weeks at the Citadel, the Charleston military college that the Marine Corps took over for this purpose. They were tested for the virus a week later and again after two weeks when they arrived.
The containment measures on campus were extensive. The recruits were ordered to wear masks at all times, except when they were asleep. keep six feet away from others; and disinfect toilets after use. Most had a single roommate and all of the training took place outdoors.
"Despite very strict procedures monitored by marine instructors 24 hours a day, we identified six transmission clusters," said Dr. Stuart Sealfon, professor of neurology at the Icahn School of Medicine, lead author on the study. These clusters resulted from a recruit who infected a roommate, or several others on the same platoon that had 50 to 60 members.
The researchers found that about 1 percent of the recruits arrived infected with the coronavirus, almost all of them without knowing it. Another 2 percent were infected during the quarantine. By the end of the study, the team had identified 77 recruits with positive tests, each of whom had been moved to a different dorm room for quarantine alone.
The outbreak on Mount Theodore Roosevelt, which began in late March and spread through May, provides a clearer picture of how the virus can invisibly spread among young people. Of 4,779 crew members, 1,271 ultimately tested positive, of whom 77 percent were asymptomatic at the time. Almost half of those who tested positive, 43 percent, never had Covid-19 symptoms; A total of 23 people were admitted to the hospital, four were admitted to the intensive care unit. One died.
"It really speaks to the stealth of the virus and how it can move asymptomatically in such a population," Cmdr said. Matthew Kasper, the Navy microbiologist who led the study. “And I think the unique situation here – we all had it tested. This was not based on any subjective sense or memory. Those are tough numbers. "
Outside experts said the two studies taken together showed not only how contagious the virus is, but what measures ideally need to be taken to contain it, be it in the military or civilian populations.
“The approaches learned from the US. Theodore Roosevelt and Parris Island can be applied to land-based shared living situations with varying relevance, ”wrote Dr. Nelson Michael of the Walter Reed Army Institute of Research in an accompanying editorial, “How dorms, prisons, and care facilities, as well as sports training environments, meat processing plants, and isolated power plants. "
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