ABSTRACT
Background. Screening large groups of individuals entering a congregate setting has been a challenge during the COVID-19 pandemic. Current Infectious Disease Society of America guidelines recommend polymerase chain reaction (PCR)-based screening in symptomatic and at-risk individuals over antigen based testing due to higher sensitivity. However, there are limited real-world data describing secondary COVID-19 cases after different arrival testing strategies. Methods. Between January 1 - August 31, 2021 all trainees attending United States Air Force Basic Military Training underwent arrival testing for COVID-19. Trainees who arrived January 1, 2021 - May 21, 2021 were tested via PCR and those from May 24, 2021 - August 31, 2021 via antigen test. All trained in groups of 30-50 and slept in communal quarters. Symptomatic secondary cases within the first two weeks of training were identified by individual as well as training group and compared based on method of arrival testing. For this study, a case cluster was defined as > 5 cases. Results. A total of 24,601 trainees arrived during the study period with 406 (1.6%) trainees testing positive on arrival, of which 134 (33%) were symptomatic. Initial positivity rate was greater for PCR testing as compared to antigen testing (2.5% vs 0.4%, RR: 5.4, 95% CI: 4.0-7.3, p< 0.001). With PCR testing, training groups were significantly more likely to have a positive case on arrival (57% vs 11%, RR: 5.3, 95% CI: 3.7-7.7, p< 0.001). However, PCR testing was not associated with a difference in training groups with a secondary case (20% vs 22%, RR: 0.9, 95% CI: 0.66-1.2, p=0.53), number of training groups with a case cluster (4% vs 6.7%, RR: 0.61, 95% CI: 0.3-1.2, p=0.16), or number of days after arrival until development of symptomatic secondary case (median 8 vs 6.5 days, p=0.37) as compared to antigen testing. Conclusion. This study describes two strategies of arrival testing for COVID-19 in a congregate setting at high risk for disease transmission. In this study, PCR-based testing was associated with more arrival cases. However, there was no difference in the number of training groups having a secondary case or a case cluster. This study supports the utility of antigen-based arrival testing for congregate settings.
ABSTRACT
Background. Symptomatic COVID-19 screening has been a cornerstone of case identification during the pandemic. Despite the myriad of COVID-19 symptoms, screens have focused on fever, cough, and dyspnea. It is unknown how well these symptoms identify cases in a healthy military population. This study aims to evaluate the utility of symptom-based screening in identifying COVID-19 through different COVID-19 waves. Methods. A convenience sample of 600 active-duty service members who arrived at JBSA in 2021 and 2022 was included in this study. We compared 200 symptomatic service members who tested positive for COVID-19 in each of FEB-APR 2021 (prior to the emergence of the Delta variant), JUN-AUG 2021 (Delta variant was predominant), and JAN 2022 (Omicron variant was predominant). Collected data included test date, reported symptoms, and vaccination status. Comparisons were conducted via Chi-Square or Fisher's Exact test. Results. Of the 600 symptomatic active-duty service members who tested positive for COVID-19, the most common symptoms were sore throat (n=385, 64%), headache (n=334, 56%), and cough (n=314, 52%). While sore throat was the most prominent symptom during Delta (n=140, 70%) and Omicron (n=153, 77%), headache was the most common prior to Delta (n=93, 47%). There were significant differences in symptoms by vaccination status (Table 2). Overall, screening for fever, cough, and dyspnea had a 65.1% sensitivity in this cohort (Table 3) with its lowest sensitivity in the pre-Delta cohort (53.5%) and highest sensitivity in the fully vaccinated Omicron cohort (78.3%). Conclusion. In this descriptive cross-sectional study evaluating symptomatic military members with COVID-19, symptom prevalence varied based on the predominant COVID-19 variant as well as patients' vaccination status. As screening strategies evolve with the pandemic, changing symptom prevalence should be considered.
ABSTRACT
Background: In March 2020, COVID-19 threatened combat operations in Afghanistan. At that time, the NATO Resolute Support mission involved nearly 17,000 troops from 38 partner nations, plus civilians who support the mission, scattered throughout Afghanistan. While Afghanistan did not initially report many confirmed cases, large numbers of cases were reported from neighboring countries with known migration across the borders (sometimes thousands/day). Military medical leaders advised commanders regarding the potential health risks to the force, balancing with risks to the mission. Quarantine and isolation protocols were established. Public health interventions of social distancing, cloth mask wear, enhanced environmental cleaning, active case finding, and emphasis on hand hygiene and cough etiquette were enforced. However, many base locations were unable to alleviate close living quarters. Testing was identified as a means to assess risk to the population. Testing capabilities were limited, particularly PCR. When this testing strategy was established, the utilization and interpretation of antibody tests was quite controversial. With rapid antibody kits, the time to detection of both IgM and IgG are similar;detection of either cannot identify the time since exposure. Methods: A novel surveillance plan was established whereby subpopulations at highest risk for exposure to the virus were screened with antibody tests from 17 Apr-1 Jun, 2020. High risk populations included: those leaving quarantine, base defense guards, isolation unit guards, medical personnel, dining facility workers, and those who interact with local populations. Individuals with detectable antibody (either IgM or IgG) were further evaluated with PCR tests. Results: In the first six weeks of this testing strategy, 1957 antibody tests were utilized. A total of 37 specimens were identified antibody positives with seroprevalence of 2% (Figure 1). Thirteen were identified to have positive IgG, 22 with IgM, and 2 with both. PCR was performed on those with detectable antibody, 13 (35%) had positive PCR. Conclusion: Serosurveillance of populations at high risk for exposure to the virus is a logical way to conserve testing resources in a constrained combat environment. (Table Presented).