Reports of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) outbreaks affecting nursing homes, homeless shelters, and cruise ships describe both asymptomatic and symptomatic cases among patients whose primary risk factor for acquisition was residence in a confined congregate environment.1-3 However, the age distribution of patients with coronavirus disease 2019 (COVID-19) described is weighted heavily toward elderly individuals and those with preexisting conditions. The USS Theodore Roosevelt (TR) outbreak investigation by the US Navy and Centers for Disease Control and Prevention illuminated how the virus affects a young military population.4 In this study, the US Army Public Health COVID-19 Task Force describes the results of an independent investigation of the shore-based USS TR outbreak response and 736 USS TR sailors in isolation status.
The Navy Bureau of Medicine and Surgery cleared this document for publication for release under Authored Works guidelines, which included a waiver of institutional review board approval for this secondary analysis and indication that this report met requirements of the Health Insurance Portability and Accountability Act privacy rules. This study follows the reporting guideline for case series.
This case series included all USS TR sailors with a diagnosis of SARS-CoV-2 infection and placed in isolation at Naval Base Guam between March 31 and April 15, 2020. Polymerase chain reaction tests for COVID-19 (BioFire Respiratory Panel With SARS-CoV-2, bioMérieux) were performed through nasal swabs for all sailors. Sailors with a diagnosis of COVID-19 were isolated. Those who tested negative for SARS-CoV-2 and those who were asymptomatic were quarantined in single-room hotel accommodations.
Daily monitoring was performed by clinical staff through face-to-face evaluations using standardized questionnaires. Sailors who developed symptoms during quarantine were retested and moved to isolation. A polymerase chain reaction test–based deisolation strategy was used for all sailors. Demographic and epidemiological characteristics and clinical and laboratory data were reviewed and analyzed.
Sailors who reported any symptom throughout the study period were characterized as symptomatic, and each symptom category was described. An epidemiological curve was created using data from 218 sailors for whom symptom onset date was documented. Data analysis was performed using R statistical software version 3.6.3 (R Project for Statistical Computing) from March to April 2020.
Of 4085 USS TR sailors who disembarked, 736 had a diagnosis of SARS-CoV-2 (median age, 25 years; interquartile range, 22-31 years; 572 men [77.7%]). Five hundred ninety sailors (80.2%) were characterized as symptomatic, with a median symptom duration of 7 days (interquartile range, 5-11 days). One hundred forty-six sailors (19.8%) remained asymptomatic for the duration of the study period. Cough was observed for 677 person-days (13.6%), coldlike symptoms for 483 person-days (9.7%), anosmia for 463 person-days (9.3%), headache for 438 person-days (8.8%), ageusia for 393 person-days (7.9%), and fever for 65 person-days (1.3%). With regard to clinical outcomes, 729 sailors remained in outpatient isolation, 6 were hospitalized, and 1 died during the study period (Table). An epidemiological curve is shown in the Figure. As shown in the Figure, the peak of the outbreak occurred on March 30, with 30 new cases.
The frequency of symptoms observed in this study is consistent with that in previous reports5 of COVID-19 among nonhospitalized patients. The person-days proportion analysis confirms that olfactory and gustatory symptoms are commonly seen in minimally symptomatic COVID-19.6 One hundred forty-six sailors (19.8%) remained asymptomatic for the duration of the study period, and this is consistent with the symptom survey results from the US Navy and Centers for Disease Control and Prevention report (18.5%),4 which also highlights the concern for enhanced asymptomatic SARS-CoV-2 transmission. Although this study is limited to the isolation group sailors during a specific period, many of the conclusions should be generalizable to the overall shipboard population.
In a confined space congregate setting with young essential workers, COVID-19 is unlikely to be clinically distinguishable from other acute respiratory illness without specific laboratory testing. Asymptomatic (and presymptomatic) spread will limit the effectiveness of symptomatic screening in the absence of other nonpharmaceutical interventions, such as testing, masking, and, as feasible, social distancing. Finally, the rapid increase in case number as incubating cases disembarked, followed by the precipitous decrease in cases, suggests that the shore-based nonpharmaceutical interventions interrupted a probable acceleration in case incidence that would have likely resulted in a substantial disease burden. Lessons learned from the USS TR COVID-19 outbreak may have applicability in other congregate settings staffed by essential workers and in understanding clinical features of the illness in younger adult populations.
Accepted for Publication: August 4, 2020.
Published: October 1, 2020. doi:10.1001/jamanetworkopen.2020.20981
Correction: This article was corrected on December 16, 2020, to fix the approval statement in the first sentence of the Methods section.
Open Access: This is an open access article distributed under the terms of the CC-BY License. © 2020 Alvarado GR et al. JAMA Network Open.
Corresponding Author: Gadiel R. Alvarado, DO, Infectious Disease Department, Brooke Army Medical Center, 3551 Roger Brooke Dr, Fort Sam Houston, TX 78234 (firstname.lastname@example.org).
Author Contributions: Dr Alvarado had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.
Concept and design: All authors.
Acquisition, analysis, or interpretation of data: Alvarado, Pierson, Gama, Cole, Jang.
Drafting of the manuscript: All authors.
Critical revision of the manuscript for important intellectual content: Alvarado, Pierson, Gama, Jang.
Statistical analysis: Alvarado, Pierson, Gama, Cole, Jang.
Administrative, technical, or material support: Alvarado, Teemer, Gama, Cole, Jang.
Supervision: Alvarado, Jang.
Conflict of Interest Disclosures: None reported.
Disclaimer: The views expressed herein are those of the authors and do not reflect the official policy or position of Brooke Army Medical Center, the US Army Medical Department, the US Army Office of the Surgeon General, the Department of the Army, the Department of the Air Force, the Department of the Navy, or the Department of Defense or the US Government.
Additional Contributions: Matthew Dolan, MD (Infectious Disease Department, Brooke Army Medical Center, Fort Sam Houston), reviewed the manuscript. He was not compensated for his time.
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