Symptom Characterization and Outcomes of Sailors in Isolation After a COVID-19 Outbreak on a US Aircraft Carrier

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.


Introduction
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][2][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.

Methods
This study was approved and granted a waiver of consent by the US Navy Bureau of Medicine and Surgery; consent was waived because the study was deemed to post minimal risk to the participants.
This study follows the reporting guideline for case series. 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.

Discussion
The frequency of symptoms observed in this study is consistent with that in previous reports 5 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