Risk Factors Associated With COVID-19 Transmission Among US Air Force Trainees in a Congregate Setting

• Published in: JAMA network open 2021-02, Vol.4 (2), p.e210202
• Main Authors: Marcus, Joseph E., Frankel, Dianne N., Pawlak, Mary T., Casey, Theresa M., Cybulski, Robert J., Enriquez, Erin, Okulicz, Jason F., Yun, Heather C.
• Format: Article
• Language: English
• Subjects: Asymptomatic; Coronaviruses; COVID-19; Disease transmission; Infections; Polymerase chain reaction; Risk factors
• ISSN: 2574-3805; 2574-3805
• DOI: 10.1001/jamanetworkopen.2021.0202

Importance Owing to concerns of coronavirus disease 2019 (COVID-19) outbreaks, many congregate settings are forced to close when cases are detected because there are few data on the risk of different markers of transmission within groups. Objective To determine whether symptoms and laboratory results on the first day of COVID-19 diagnosis are associated with development of a case cluster in a congregate setting. Design, Setting, and Participants This cohort study of trainees with COVID-19 from May 11 through August 24, 2020, was conducted at Joint Base San Antonio–Lackland, the primary site of entry for enlistment in the US Air Force. Symptoms and duration, known contacts, and cycle threshold for trainees diagnosed by reverse transcription–polymerase chain reaction were collected. A cycle threshold value represents the number of nucleic acid amplification cycles that occur before a specimen containing the target material generates a signal greater than the predetermined threshold that defines positivity. Cohorts with 5 or more individuals with COVID-19 infection were defined as clusters. Participants included 10 613 trainees divided into 263 parallel cohorts of 30 to 50 people arriving weekly for 7 weeks of training. Exposures All trainees were quarantined for 14 days on arrival. Testing was performed on arrival, on day 14, and anytime during training when indicated. Protective measures included universal masking, physical distancing, and rapid isolation of trainees with COVID-19. Main Outcomes and Measures Association between days of symptoms, specific symptoms, number of symptoms, or cycle threshold values of individuals diagnosed with COVID-19 via reverse transcription–polymerase chain reaction and subsequent transmission within cohorts. Results In this cohort study of 10 613 US Air Force basic trainees in 263 cohorts, 403 trainees (3%) received a diagnosis of COVID-19 in 129 cohorts (49%). Among trainees with COVID-19 infection, 318 (79%) were men, and the median (interquartile range [IQR]) age was 20 (19-23) years; 204 (51%) were symptomatic, and 199 (49%) were asymptomatic. Median (IQR) cycle threshold values were lower in symptomatic trainees compared with asymptomatic trainees (21.2 [18.4-27.60] vs 34.8 [29.3-37.4];P < .001). Cohorts with clusters of individuals with COVID-19 infection were predominantly men (204 cohorts [89%] vs 114 cohorts [64%];P < .001), had more symptomatic trainees (146 cohorts [64%] vs 53 cohorts [30%];P < .001), and had mor