SARS-CoV-2 Positivity on or After 9 Days Among Quarantined Student Contacts of Confirmed Cases | Infectious Diseases | JAMA | JAMA Network
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Table.  SARS-CoV-2 Positivity Rates Among Quarantined Student Contacts of Confirmed COVID-19 Cases
SARS-CoV-2 Positivity Rates Among Quarantined Student Contacts of Confirmed COVID-19 Cases
1.
Macartney  K, Quinn  HE, Pillsbury  AJ,  et al; NSW COVID-19 Schools Study Team.  Transmission of SARS-CoV-2 in Australian educational settings: a prospective cohort study.   Lancet Child Adolesc Health. 2020;4(11):807-816. doi:10.1016/S2352-4642(20)30251-0PubMedGoogle ScholarCrossref
2.
Cevik  M, Tate  M, Lloyd  O, Maraolo  AE, Schafers  J, Ho  A.  SARS-CoV-2, SARS-CoV, and MERS-CoV viral load dynamics, duration of viral shedding, and infectiousness: a systematic review and meta-analysis.   Lancet Microbe. 2021;2(1):e13-e22. doi:10.1016/S2666-5247(20)30172-5PubMedGoogle ScholarCrossref
3.
Davies  NG, Klepac  P, Liu  Y, Prem  K, Jit  M, Eggo  RM; CMMID COVID-19 Working Group.  Age-dependent effects in the transmission and control of COVID-19 epidemics.   Nat Med. 2020;26(8):1205-1211. doi:10.1038/s41591-020-0962-9PubMedGoogle ScholarCrossref
4.
Lednicky  JA, Lauzardo  M, Fan  ZH,  et al.  Viable SARS-CoV-2 in the air of a hospital room with COVID-19 patients.   Int J Infect Dis. 2020;100:476-482. doi:10.1016/j.ijid.2020.09.025PubMedGoogle ScholarCrossref
5.
US Centers for Disease Control and Prevention. Options to reduce quarantine for contacts of persons with SARS-CoV-2 infection using symptom monitoring and diagnostic testing. Accessed February 12, 2021. https://www.cdc.gov/coronavirus/2019-ncov/more/scientific-brief-options-to-reduce-quarantine.html
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    3 Comments for this article
    EXPAND ALL
    Day 6-7 Testing for Schools?
    Rebecca Ivatury, MHA, BSN, BS, RN | K-8 school
    Any guidance, and data, on PCR-testing at day 6-7 with a return to school after day 7 in the congregated school setting? I see the CDC states transmission risk increases 5% with this option - is that taking into account all the mitigation that schools are doing or is the 5% just for all/general purposes? Any insight on how it relates to school - a comparison with this testing regimen at day 6 or 7 similar to how this was done for day 9 testing? Thank you, from a school nurse in Lyme, New Hampshire
    CONFLICT OF INTEREST: None Reported
    RT-PCR test infection or exposure
    Henry Kaldenbaugh, M.D | Yavapai County Health Department
    Nasal mucous and saliva are part of our immune mechanism to fight viral and bacterial infections.
    If an RT-PCR test is positive, it indicates presence of viral RNA in the secretion. This is not necesssarily an infection. Especially if the RT-PCR flourescence occurs after cycle 25 it is detecting few viral RNA strands. If it turns positive after cycle 35, it could indicate only one small fragment of RNA in the secretion.
    Conversely, if it turns positive before cycle 20, It probably indicates infection and viral shedding.
    Are asymptomatic carriers infected or only exposed without enough virus
    to cause infection?
    CONFLICT OF INTEREST: None Reported
    READ MORE
    Details Matter
    Binh Ngo, M.D. | Keck USC School of Medicine
    This is a very important paper to study patterns of transmission of SARS-Cov-2 in a cohort of school children. For those interested in modeling disease transmission this data is very valuable. Perhaps the best study to date of transmission in a social network was a Spanish study comparing hydroxychloroquine prophylaxis to placebo (1). In that study the nominal transmission rate was about 18%. But there is much missing detail in this report:

    1) How did the symptoms correlate with PCR results?

    2) Were there any hospitalizations?

    3) Did they
    include the parents in their testing protocol?

    4) How long was the school day for elementary versus middle school students versus high school students?

    5) What were respective class sizes?

    Perhaps medRxiv would be a reasonable choice for a full exposition.

    Reference

    1) Mitjà O, Corbacho-Monné M, UbalsM, et al. A Cluster-Randomized Trial of Hydroxychloroquine for Prevention of Covid-19. N Engl J Med. 2021;384(5):417–427.
    CONFLICT OF INTEREST: None Reported
    READ MORE
    Research Letter
    February 19, 2021

    SARS-CoV-2 Positivity on or After 9 Days Among Quarantined Student Contacts of Confirmed Cases

    Author Affiliations
    • 1Department of Pediatrics, University of Florida College of Medicine, Gainesville
    • 2Department of Environmental and Global Health, University of Florida, College of Public Health and Health Professions, Gainesville
    • 3Florida Department of Health, Jacksonville
    • 4Florida Department of Health, Gainesville
    • 5Emerging Pathogens Institute, University of Florida, Gainesville
    JAMA. 2021;325(15):1561-1562. doi:10.1001/jama.2021.2392

    Schools reopened during the fall of 2020 with various approaches to mitigate SARS-CoV-2 infection. At that time, the US Centers for Disease Control and Prevention (CDC) recommended a 14-day quarantine without testing for close contacts of anyone diagnosed with COVID-19.

    However, data indicated that the incubation period for SARS-CoV-2 infection is 4 to 5 days from exposure in adults and is 6 to 7 days from exposure in children,1-3 suggesting that most infected students should test positive by day 9. Therefore, Alachua County, Florida, implemented SARS-CoV-2 testing on day 9 and return to school on day 10 for student contacts of confirmed COVID-19 cases. We evaluated test positivity rates for SARS-CoV-2 infection among these student contacts.

    Methods

    The project was reviewed by the University of Florida and the Florida Department of Health institutional review boards and was determined to meet the criteria for a public health surveillance activity exclusion. Signed informed consent was obtained from parents before sample collection. Alachua County has 49 schools serving a population of 26 456 kindergarten through 12th-grade students. A hybrid model of virtual and in-person instruction was offered; 49% of students were enrolled for in-person instruction.

    The Alachua County Health Department provided reverse transcriptase–polymerase chain reaction (RT-PCR) testing of nasopharyngeal swabs for symptomatic students (suspected cases) and contact tracing for COVID-19–positive confirmed cases; RT-PCR and rapid antigen test results from private physicians were included for case confirmation. The methods for genetic testing of isolates have been described.4 Student contacts of confirmed COVID-19 cases were quarantined and offered RT-PCR testing at day 3 (to exclude students who might have been infected at the same time as the confirmed case) and at day 9; testing was sometimes delayed to days 10 to 14. Asymptomatic students who tested negative on days 9 to 14 could return to school on the day following their negative test. If no testing was administered, a 14-day quarantine was required.

    The percentage of student contacts who tested positive on days 9 to 14 was determined. Students who returned to school after a negative test result were monitored for symptoms through day 14. The percentage of COVID-19–positive contacts among elementary and middle school students vs high school students was compared using the Fisher exact test with statistical significance set at P < .05 (2-sided) using R version 3.4.1 and R Studio version 1.1.0153 (R Foundation for Statistical Computing for both). Instructional days missed were compared with days that would have been missed if all student contacts of confirmed COVID-19 cases had been quarantined for 14 days.

    Results

    Between August 1 and November 30, 2020, when the Alachua County SARS-CoV-2 test positivity rate was 4.9%, 495 suspected student cases were tested and 257 (51.9%) were positive for SARS-CoV-2 infection. For these 257 confirmed cases of SARS-CoV-2 infection, 2189 contacts were quarantined, 134 (6.1%) were tested on day 3, and 839 (38.3%) were tested on days 9 to 14. Of the 134 student contacts tested on day 3, 14 (10.4%) were positive for SARS-CoV-2 infection. Of the 839 student contacts tested on days 9 to 14, 40 (4.8%) were positive for SARS-CoV-2 infection. Of the 388 student contacts in high school who were tested, 32 (8.2%) were positive for SARS-CoV-2 infection on days 9 to 14 compared with 8 (1.8%) of 451 student contacts in elementary and middle school who tested positive (P < .001; Table).

    Among 799 student contacts of confirmed COVID-19 cases with a negative test result on days 9 to 14, only 1 student became symptomatic after returning to school and had a positive SARS-CoV-2 test result on day 14 after an initial negative test result on day 9. The virus from this student was genetically distinct from the virus isolated from the confirmed COVID-19 case to which the student had been exposed (GenBank confirmed case: MW307809; GenBank 9-day student contact: MW308137). Loss of instruction decreased by 3649 days with the 9-day testing protocol (8097 days missed) compared with a theoretical 14-day quarantine without testing (11 746 days missed).

    Discussion

    In this study of a 9-day testing protocol for student contacts of confirmed COVID-19 cases in 1 Florida county, a reduction in loss of instructional time was found that was less than what would have occurred with a 14-day quarantine. There was no evidence that an earlier return to school with a negative test result was linked with subsequent symptomatic illness. Had students returned to school before day 14 without testing on day 9 or thereafter, 8.2% of high school contacts would have returned to school with SARS-CoV-2 infection. These findings should be considered when evaluating the December 2020 CDC recommendation for a 10-day quarantine without testing or a 7-day quarantine with testing.5

    Limitations of this study include (1) contact testing ranging from days 9 to 14; (2) lack of testing for students who quarantined for 14 days; and (3) use of symptomatic illness alone for follow-up of negative test results.

    Section Editor: Jody W. Zylke, MD, Deputy Editor.
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    Article Information

    Corresponding Author: Eric J. Nelson, MD, PhD, MS, Emerging Pathogens Institute, University of Florida, 2055 Mowry Rd, Gainesville, FL 32611 (eric.nelson@ufl.edu).

    Accepted for Publication: February 9, 2021.

    Published Online: February 19, 2021. doi:10.1001/jama.2021.2392

    Author Contributions: Mr Myers had full access to all the data in the study and takes responsibility for the integrity of the data and Dr Morris takes responsibility for the accuracy of the data analysis.

    Concept and design: Nelson, McKune, Ryan, Lednicky, Morris.

    Acquisition, analysis, or interpretation of data: All authors.

    Drafting of the manuscript: Nelson, McKune, Ryan, Morris.

    Critical revision of the manuscript for important intellectual content: All authors.

    Statistical analysis: Nelson, Morris.

    Administrative, technical, or material support: McKune, Ryan, Lednicky, Myers.

    Supervision: McKune, Ryan, Morris.

    Conflict of Interest Disclosures: None reported.

    Additional Contributions: We acknowledge the data aggregation and analysis efforts of Michael Smith, RN, and Cameron Livingston, RN (both with the Alachua County Health Department); the insight and guidance of the Scientific and Medical Advisory Committee members Michael Lauzardo, MD, and Yana Banks, MD (both University of Florida faculty members); and the commitment of the School Board of Alachua County, the Florida Department of Health, the Alachua County Health Department, and the families of Alachua County to keep schools open and safe from COVID-19. No compensation was received by any of these individuals for their role in this study.

    Additional Information: Testing, contact tracing, and follow-up were conducted as part of the Alachua County Health Department surveillance of SARS-CoV-2 infection in the Alachua County Schools. Deidentified data were analyzed and shared with permission from the Alachua County Health Department.

    References
    1.
    Macartney  K, Quinn  HE, Pillsbury  AJ,  et al; NSW COVID-19 Schools Study Team.  Transmission of SARS-CoV-2 in Australian educational settings: a prospective cohort study.   Lancet Child Adolesc Health. 2020;4(11):807-816. doi:10.1016/S2352-4642(20)30251-0PubMedGoogle ScholarCrossref
    2.
    Cevik  M, Tate  M, Lloyd  O, Maraolo  AE, Schafers  J, Ho  A.  SARS-CoV-2, SARS-CoV, and MERS-CoV viral load dynamics, duration of viral shedding, and infectiousness: a systematic review and meta-analysis.   Lancet Microbe. 2021;2(1):e13-e22. doi:10.1016/S2666-5247(20)30172-5PubMedGoogle ScholarCrossref
    3.
    Davies  NG, Klepac  P, Liu  Y, Prem  K, Jit  M, Eggo  RM; CMMID COVID-19 Working Group.  Age-dependent effects in the transmission and control of COVID-19 epidemics.   Nat Med. 2020;26(8):1205-1211. doi:10.1038/s41591-020-0962-9PubMedGoogle ScholarCrossref
    4.
    Lednicky  JA, Lauzardo  M, Fan  ZH,  et al.  Viable SARS-CoV-2 in the air of a hospital room with COVID-19 patients.   Int J Infect Dis. 2020;100:476-482. doi:10.1016/j.ijid.2020.09.025PubMedGoogle ScholarCrossref
    5.
    US Centers for Disease Control and Prevention. Options to reduce quarantine for contacts of persons with SARS-CoV-2 infection using symptom monitoring and diagnostic testing. Accessed February 12, 2021. https://www.cdc.gov/coronavirus/2019-ncov/more/scientific-brief-options-to-reduce-quarantine.html
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