CMAAO Coronavirus Facts and Myth Buster: Efficacy of public health measures to control the transmission of COVID-19 in young adults |
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CMAAO Coronavirus Facts and Myth Buster: Efficacy of public health measures to control the transmission of COVID-19 in young adults
Dr KK Aggarwal,  21 November 2020
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With input from Dr Monica Vasudev

1149: The efficacy of public health measures to control the transmission of COVID-19 in young adults.

NEJM EXCERPTS: A study evaluated SARS-CoV-2 infections among U.S. Marine Corps recruits who were subjected to a 2-week quarantine at home and a second supervised 2-week quarantine at a closed college campus that required them to wear mask, practice social distancing, and daily temperature and symptom monitoring. The volunteers were tested for SARS-CoV-2 using quantitative polymerase-chain-reaction (qPCR) assay of nares swab specimens obtained between arrival and the second day of supervised quarantine and on days 7 and 14. Those who did not volunteer for the study were subjected to qPCR testing only on day 14, at the end of the quarantine period. Phylogenetic analysis of viral genomes obtained from infected study volunteers was done to determine clusters and to assess the epidemiologic features of infections.

Overall, 1848 recruits volunteered to participate in the study and within 2 days of arrival on campus, 16 (0.9%) tested positive for the virus. Fifteen of these were asymptomatic.

Thirty five 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 prior to a positive test. Among the recruits who did not participate in the study, 26 (1.7%) of the 1554 recruits with available qPCR results tested positive on day 14.

Investigators identified no SARS-CoV-2 infections through clinical qPCR testing performed as a result of daily symptom monitoring. An evaluation of 36 SARS-CoV-2 genomes obtained from 32 participants exhibited six transmission clusters among 18 participants. Epidemiologic analysis suggested multiple local transmission events, including transmission between roommates and among recruits within the same platoon.

Viral genomes were recovered from nearly two-thirds of the infected participants. Phylogenetic analysis of the genomes could identify six independent monophyletic transmission clusters pointing to local transmission during the supervised quarantine. Most clusters included members of the same platoon, and several of the infected recruits had an infected roommate. The two largest sequence-defined clusters were evident in the same class of recruits, and each cluster occurred within a platoon, except one recruit, who was roomed with an infected recruit from another platoon and was infected with a strain belonging to the same cluster as that identified in other members of that platoon.


While several infected recruits in both the clusters had nearby room assignments and shared a bathroom, the epidemiologic analysis indicated that platoon membership and double-occupancy rooming were the risk factors for infection, and room proximity and shared bathrooms were not.

Among Marine Corps recruits, about 2% who previously had negative results for SARS-CoV-2 at the outset of supervised quarantine, and <2% of recruits with unknown previous status, tested positive by day 14 in the study. Most recruits testing positive were asymptomatic, and no infections were identified by means of daily symptom monitoring. Transmission clusters occurred within platoons.

The study thus revealed that in a group of predominantly young male military recruits, about 2% became positive for SARS-CoV-2 during a 2-week, strict quarantine. Several, independent virus strain transmission clusters were detected. Shared rooms and shared platoon membership were identified as the risk factors for transmission. Most study participants with positive qPCR tests were asymptomatic, and all cases among participants and nonparticipants were detected through scheduled testing rather than clinical qPCR testing performed based on daily screening.

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Dr KK Aggarwal

President CMAAO, HCFI and Past National President IMA

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