SARS-CoV-2 Transmission among Marine Recruits during Quarantine

Abstract

Background The efficacy of public health measures to control the transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has not been well studied in young adults. Methods We investigated SARS-CoV-2 infections among U.S. Marine Corps recruits who underwent a 2-week quarantine at home followed by a second supervised 2-week quarantine at a closed college campus that involved mask wearing, social distancing, and daily temperature and symptom monitoring. Study volunteers were tested for SARS-CoV-2 by means of quantitative polymerase-chain-reaction (qPCR) assay of nares swab specimens obtained between the time of arrival and the second day of supervised quarantine and on days 7 and 14. Recruits who did not volunteer for the study underwent qPCR testing only on day 14, at the end of the quarantine period. We performed phylogenetic analysis of viral genomes obtained from infected study volunteers to identify clusters and to assess the epidemiologic features of infections. Results A total of 1848 recruits volunteered to participate in the study; within 2 days after arrival on campus, 16 (0.9%) tested positive for SARS-CoV-2, 15 of whom were asymptomatic. An additional 35 participants (1.9%) tested positive on day 7 or on day 14. Five of the 51 participants (9.8%) who tested positive at any time had symptoms in the week before a positive qPCR test. Of the recruits who declined to participate in the study, 26 (1.7%) of the 1554 recruits with available qPCR results tested positive on day 14. No SARS-CoV-2 infections were identified through clinical qPCR testing performed as a result of daily symptom monitoring. Analysis of 36 SARS-CoV-2 genomes obtained from 32 participants revealed six transmission clusters among 18 participants. Epidemiologic analysis supported multiple local transmission events, including transmission between roommates and among recruits within the same platoon. Conclusions Among Marine Corps recruits, approximately 2% who had previously had negative results for SARS-CoV-2 at the beginning of supervised quarantine, and less than 2% of recruits with unknown previous status, tested positive by day 14. Most recruits who tested positive were asymptomatic, and no infections were detected through daily symptom monitoring. Transmission clusters occurred within platoons. (Funded by the Defense Health Agency and others.)

The Proportion of SARS-CoV-2 Infections That Are Asymptomatic

“…Nineteen of the PCR-based studies collected data on symptoms longitudinally after testing, making it possible to distinguish between presymptomatic and asymptomatic infection ( 15 , 17 , 18 , 20 , 22 , 25 , 26 , 27 , 32 , 37–40 , 45 , 47 , 48 , 51 , 53 , 54 ). The follow-up period in these studies ranged from 2 to 70 days, with a median of 14 days (IQR, 14.0 to 15.8 days).…”

SARS-CoV-2 in the U.S. Military — Lessons for Civil Society

“…The Department of Health and Human Services and the Department of Defense are using a framework to efficiently develop, test, and implement medical solutions to prevent, detect, and treat severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Two articles now published in the Journal (online November 11) 2 , 3 speak to this historical dialogue — they show how medical practices used in the military could inform civilian public health practices with respect to shared living situations during the Covid-19 pandemic.…”

“…Letizia and colleagues 3 examine the effect of a phased quarantine of 1848 recruits reporting to Marine Corps Recruit Depot, Parris Island, South Carolina. Recruits completed a 2-week self-quarantine period at home, followed by a 2-week supervised quarantine on a college campus after assignment to platoons, which consisted of 50 to 60 recruits.…”

Medical care and first aid: an interassociation consensus framework for organised non-elite sport during the COVID-19 pandemic

“…Following COVID-19 infection, participants should self-isolate for 10 days 19 and not engage in exercise until they have been symptom free for 7 days. 20 Participants experiencing cardiac symptoms including an elevated resting heart rate after the acute infection has resolved should seek specialist medical attention prior to return to exercise.…”