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SARS-CoV-2 Transmission among Marine Recruits during Quarantine


Study design and participants

To reduce the risk of introducing SARS-CoV-2 in basic training at the Marine Corps Recruitment Depot, Parris Island, in South Carolina, the Marine Corps supervised a 14-day college campus specifically used for this purpose Established the quarantine period. Potential recruits were instructed to leave the house for 2 weeks immediately before traveling to campus. At the end of the second, supervised quarantine on campus, a negative qPCR result was required for all recruits before entering Paris Island. Recruits were asked to participate in the COVID-19 Health Action Response for Marine (CHARM) study, which included a weekly qPCR test and a blood sample for IgG antibody evaluation.

After prospective recruits had completed the 14-day home quarantine, they were presented to a local military entry processing station, where a medical history was taken and a physical examination performed. If potential recruits were considered physically and mentally fit for recruitment, they were instructed to wear masks at all times and to maintain a social distance of at least 6 feet during a visit to the quarantine premises. Classes of 350 to 450 recruiters visit the campus almost weekly. The new classes were divided into platoons of 50 to 60 recruits, and roommates were assigned to participate independently in the CHARM study. Overlapping classes were housed in separate dormitories and eating times and training schedules varied.

During supervised quarantine, public health measures were implemented to suppress SARS-CoV-2 transmissions (Table S1 in) Supplementary Addendum, With full text of this article available at NEJM.org). All recruits wore double-layered cloth masks indoors and out at all times, except sleeping or eating; Practiced a social distance of at least 6 feet; No one was allowed to leave the premises; Not having access to personal electronics and other objects that may contribute to surface transmission; And wash their hands regularly. They slept in double-occupancy rooms with sinks, ate in shared dining facilities and used shared bathrooms. All recruits cleaned their rooms daily, sanitized bathrooms after each use with bleach wipes, and ate pre-made food in the dining hall that was cleaned with bleach after each platoon was eaten. Most instructions and exercises were carried out. All movement of recruits was overseen, and unidirectional flow was applied along specified building entry and exit points to minimize contact between individuals. All recruits undergo a daily temperature and symptom check, regardless of participation in the study. The six instructors assigned to each cohort worked in an 8-hour shift and implemented quarantine measures. If recruits reported any signs or symptoms consistent with Kovid-19, they were reported to be undergoing rapid qPCR testing for sick calls, SARS-COV-2, and the test results were kept in pending isolation.

Instructors were also prohibited on campus, required to wear masks, provided prefabricated food, and undergo daily temperature checks and symptom checks. Instructors who were assigned to a platoon in which a positive case was diagnosed rapidly underwent qPCR testing for SARS-CoV-2, and the instructor was removed from duty if the results were positive. Recruits and instructors were prohibited from interacting with campus support staff, such as watchmen and food-service personnel. After each classroom quarantine, a deep bleach cleaning of the surfaces was carried out in the bathroom, showers, bedrooms, and hallway in the hallway, and the dormitory was kept uninterrupted for at least 72 hours before recombination.

Within 2 days of arrival on campus, Plato and the roommates had received assignments after being admitted, providing them with the opportunity to participate in a longitudinal CHARM study. Recruits were eligible if they were 18 years of age or older and if they would be available for follow-up. The study was approved by the Institutional Review Board of the Naval Medical Research Center and complied with all applicable federal regulations governing the safety of human subjects. All participants provided written informed consent.

The processes

At the time of enrollment, participants responded to a questionnaire regarding demographic characteristics, risk factors for SARS-CoV-2 infection, symptoms within the last 14 days, and a brief medical history; Blood samples and mid-turbine nerve swab samples were obtained for qPCR testing to detect SARS-CoV-2. Demographic information includes gender, age, ethnic group, race, place of birth, and US state or place of residence; Information about risk factors included whether participants had used masks, whether they had undergone self-quarantine prior to arrival, their recent travel history, their going to someone with a Kovid-19- Identified contacts, whether they were inflammatory symptoms or other respiratory illness, and whether they were any of the 14 specific symptoms of Kovid-19 or any other symptoms associated with the unspecified condition within the last 14 days.

Study participants on days 7 and 14 were followed up, at which time they reported any symptoms within the previous 7 days. Male swab samples were also obtained for repeated qPCR assays. Participants who had positive qPCR results were kept in isolation and were approached to participate in a related but separate study of infected recruits, including more frequent trials during isolation. All recruits who did not participate in the current study were tested for SARS-CoV-2 only at the end of 2-week quarantine, unless clinically indicated (Marine Corps public health According to procedures). Serum samples obtained during enrollment were tested for SARS-CoV-2-specific IgG antibodies with the use of the methods described below Supplementary Addendum.

Participants who tested positive on Day of Enrollment (Day 0) or 7 or Day 14 were separated from their rooms and kept in isolation. Otherwise, participants and non-counterparties were not treated differently: they followed the same safety protocol, were assigned to rooms and platoons regardless of participation in the study, and received the same formal instructions. did.

Laboratory methods

The qPCR of the mid-turbine Narease swab sample for SARS-CoV-2 was performed within 48 hours after collection by Lab24 (Boca Raton, FL) with the use of the TableV Covid-19 Combo Kit (Thermo Fisher Scientific), Which is authorized by the Food and Drug Administration. Samples obtained from nonparents were tested by the Naval Medical Research Center (Silver Spring, MD). Samples were stored in viral transport medium at 4 ° C. The presence of IgG antibodies specific for the SARS-CoV-2 receptor-binding (spike) domain in serum samples was evaluated as previously described, with the use of an enzyme-linked immunosorbent assay as previously described was evaluated.10 With some modifications. At least two positive controls, eight negative controls (serum samples obtained before July 2019), and four blank (no serum) were included in each plate. Serum samples were first shown at 1:50 dilution, followed by a series of complete dilution if found completely positive.

Whole-genome sequencing and assembly

SARS-CoV-2 sequencing was performed with the use of two sequencing protocols (an Illumina sequencing protocol and an ion torrent sequencing protocol) to increase the likelihood of obtaining complete genome sequencing. A custom context-based analysis pipeline (https://github.com/mjsull/COVID_pipe) Was used to access the SARS-CoV-2 genome using data from Illumina, Ion Torrent, or both.1 1

phylogenetic analysis

SARS-CoV-2 genomes were obtained from patients around the world and related metadata, influenza data downloaded from the Global Initiative to share the Epidio V database.12 A subset of the sequence was selected from this database on August 11, 2020 (79,840 sequences), and using the next generation software’s default subsampling scheme13 With the aim of maximizing the representation of genomes derived from patients in the United States. Phylogenetic analyzes of samples obtained from participants were performed with the v1.0-292-ga9de690 Nextstrain build for the SARS-CoV-2 genome with the use of default parameters. Transmission and outbreak events were identified based on clustering of the SARS-CoV-2 genome obtained from study participants within the Nextstrain phylogenetic tree conceived with TreeTime.14 A comparative analysis of the mutation profiles relative to the SARS-CoV-2 Wuhan reference genome was performed with the use of Nextclade software, version 0.3.6 (https://clades.nextstrain.org/).

Data analysis

Harnees who had previously tested positive for SARS-CoV-2 by the qPCR assay on each day of testing were excluded from the study, who had previously tested positive. Administratively separated from the Marine Corps. , Or missing data was. The computation of the cumulative positivity rate included all recruits who had tested at previous time points, including those who were no longer participating in the study. Only descriptive numerical results and percentages are reported, with no formal statistical analysis.



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