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Published on: October 3, 2016
Risk Factors Associated With COVID-19 Transmission Among US Air Force Trainees in a Congregant Setting
Joseph E Marcus1, Dianne N Frankel2, Mary T Pawlak2
1Infectious Diseases Service, Brooke Army Medical Center, Joint Base San Antonio, Texas.
Insights
Higher symptom counts and lower cycle threshold values in symptomatic individuals with coronavirus disease 2019 (COVID-19) were linked to increased transmission in group settings. These findings can help predict COVID-19 outbreaks in congregant settings.
Area of Science:
- Epidemiology
- Infectious Diseases
- Public Health
Background:
- Congregant settings face closures due to coronavirus disease 2019 (COVID-19) outbreaks, with limited data on transmission risks.
- Understanding transmission markers is crucial for managing outbreaks in shared environments.
Purpose of the Study:
- To investigate the association between initial COVID-19 symptoms and laboratory results with case cluster development in a congregant setting.
- To identify predictive markers for COVID-19 transmission within groups.
Main Methods:
- A cohort study involving 10,613 US Air Force trainees in 263 parallel cohorts.
- Data collected included symptoms, duration, contacts, and cycle threshold values from reverse transcription-polymerase chain reaction (RT-PCR) testing.
- Cohorts with 5 or more COVID-19 cases were defined as clusters.
Main Results:
- 3% of trainees (403) were diagnosed with COVID-19. Symptomatic trainees had significantly lower median cycle threshold values (21.2) compared to asymptomatic trainees (34.8).
- Cohorts with COVID-19 clusters showed a higher proportion of symptomatic trainees and lower median cycle threshold values.
- Increased symptom count and lower cycle threshold values were associated with subsequent cluster development within cohorts.
Conclusions:
- Higher symptom burden and lower cycle threshold values in individuals with COVID-19 are associated with increased transmission and cluster formation in congregant settings.
- These markers may serve as valuable indicators for predicting and managing COVID-19 outbreaks in similar environments.
Importance:
Owing to concerns of coronavirus disease 2019 (COVID-19) outbreaks, many congregant 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 congregant 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 more median (IQR) symptoms per patient (3 [2-5] vs 1 [1-2]; P < .001) compared with cohorts without clusters. Within cohorts, subsequent development of clusters of 5 or more individuals with COVID-19 infection compared with those that did not develop clusters was associated with cohorts that had more symptomatic trainees (31 of 58 trainees [53%] vs 43 of 151 trainees [28%]; P = .001) and lower median (IQR) cycle threshold values (22.3 [18.4-27.3] vs 35.3 [26.5-37.8]; P < .001).
Conclusions And Relevance:
In this cohort study of US Air Force trainees living in a congregant setting during the COVID-19 pandemic, higher numbers of symptoms and lower cycle threshold values were associated with subsequent development of clusters of individuals with COVID-19 infection. These values may be useful if validated in future studies.
