Colored scanning electron microscope image of an apoptotic cell (green) that is heavily infected with SARS-COV-2 virus particles (yellow) and that was isolated from a patient sample. The image was taken at the NIAID Integrated Research Facility (IRF) in Fort Detrick, Maryland. Photo credit: NIH / NIAID

A study of nearly 2,000 Marine recruits who had undergone supervised quarantine prior to beginning basic training found multiple cases of asymptomatic transmission of SARS-CoV-2, the virus that causes COVID-19, despite the quarantine measures.

The results have important implications for the effectiveness of public health measures to suppress the transmission of COVID-19 among young adults, whether in military training, schools, or other aspects of the pandemic.

Researchers at Mount Sinai’s Icahn School of Medicine and the Naval Medical Research Center examined new Marine recruits while they were in a two-week supervised quarantine. The study results, published November 11 in the New England Journal of Medicine, showed that few infected recruits had symptoms before SARS-CoV-2 infection was diagnosed, that transmission despite implementation of many proven measures in the area public health was done and that diagnoses were made only through scheduled testing, not testing done in response to symptoms.

“We were honored that the US Navy gave us the opportunity to work together with Navy recruits on the study of SARS-CoV-2,” says Dr. Stuart Sealfon, Professor of Neurology at the Icahn School of Medicine, Sara B. and Seth M. Glickenhaus on Mount Sinai. “This is a difficult-to-suppress infection in young people, even when mask wear, social distancing, and other harm control measures are closely monitored. We find that regular testing, not based on symptoms, identifies wearers who are SARS-CoV-2. We hope this information will help develop more effective measures to protect military facilities and schools. “

Study data showed asymptomatic spread of the virus, even under strict military orders for quarantine and health measures, which most likely saw better compliance than would be possible in other youth settings like college. The researchers found that daily temperature and symptom tests did not reveal any infections in the recruits, and that the virus was largely transmitted within a specific platoon that trainees tended to be close to each other.

The study focused on 1,848 subjects enrolled between May 15 and the end of July from nine different Navy recruit classes, each with 350 to 450 recruits. Participants were offered to enroll in a prospective longitudinal study after quarantining themselves at home for two weeks before going to basic training. On arrival, they had to adhere to strict group quarantine measures with two-person rooms for two weeks – the duration of the study period – before the actual training began. The supervised group quarantine took place at a college used only for this purpose. Each recruit class was housed in different buildings and had different meal times and training schedules so the classes did not interact with each other.

Each weekly class was further divided into platoons of 50-60. During the study period, all recruits wore cloth masks, maintained a social distance of at least two meters, and washed their hands regularly. Each recruit only had one roommate. Most of their classes, including practicing and learning military customs and traditions, were conducted outdoors. After each class finished quarantine, all rooms and public areas of the dormitories were thoroughly cleaned with bleach on the surfaces prior to the arrival of the next class.

To determine asymptomatic and symptomatic SARS-CoV-2 prevalence and transmission during the monitored quarantine, participants were tested within 2 days of arrival, after 7 days, and after 14 days using a nasal swab test (PCR), which is available for the emergency is approved by US Food and Drug Administration. Analysis of viral genomes from infected recruits identified multiple clusters that were temporally, spatially, and epidemiologically related, and revealed multiple local transmission events during quarantine.

“The identification of six independent transmission clusters defined by different mutations shows that there were multiple independent SARS-CoV-2 introductions and outbreaks during the monitored quarantine,” said Dr. Harm van Bakel, Assistant Professor of Genetics and Genomic Sciences at the Icahn School of Medicine on Mount Sinai. “The data from this large study shows that in order to limit coronavirus transmission in group settings and prevent it from spreading to the wider community, we must conduct comprehensive initial and repeat surveillance testing of all individuals regardless of symptoms.”

The insight into COVID-19 traits and SARS-CoV-2 transmission among military personnel is relevant to developing safe approaches for related environments composed primarily of young adults such as schools, sports and camps.

“Our study underscores the ability of Navy Medicine research to overcome and overcome many logistical hurdles during a pandemic and to rapidly produce an institutional review board-approved study. These results will improve the medical preparedness of our Marines and should help guide public health policy fully inform the Navy, the Department of Defense and society at large to reduce the transmission of SARS CoV-2, “said Cmdr. Andrew Letizia, MD, assistant director of the Infectious Disease Directorate for the Naval Medical Research Center and lead researcher for the study.

Follow the latest news on the Coronavirus (COVID-19) outbreak provided by the Mount Sinai Hospital

Quote: A study of almost 2,000 marine recruits shows asymptomatic SARS-CoV-2 transmission (2020, November 11th), which was reported on November 11th, 2020 from https://medicalxpress.com/news/2020-11-marine- reveals-asymptomatic-sars-cov- was obtained. Transmission.html

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