Optimizing SARS-CoV-2 Surveillance in the United States: Insights From the National Football League Occupational Health Program

The "Bubble": What Can Be Learned from the National Basketball Association (NBA)'s 2019-20 Season Restart in Orlando during the COVID-19 Pandemic

BACKGROUND

The National Basketball Association (NBA) suspended operations in response to the COVID-19 pandemic in March 2020. To safely complete the 2019-20 season, the NBA created a closed campus in Orlando, Florida, known as the NBA "Bubble." More than 5000 individuals lived, worked, and played basketball at a time of high local prevalence of SARS-CoV-2.

METHODS

Stringent protocols governed campus life to protect NBA and support personnel from contracting COVID-19. Participants quarantined before departure and upon arrival. Medical and social protocols required that participants remain on campus, test regularly, physically distance, mask, use hand hygiene, and more. Cleaning, disinfection, and air filtration was enhanced. Campus residents were screened daily and confirmed cases of COVID-19 were investigated.

RESULTS

In the Bubble population, 148 043 COVID-19 reverse transcriptase PCR (RT-PCR) tests were performed across approximately 5000 individuals; Orlando had a 4% to 15% test positivity rate in this timeframe. There were 44 COVID-19 cases diagnosed either among persons during arrival quarantine or in non-team personnel while working on campus after testing but before receipt of a positive result. No cases of COVID-19 were identified among NBA players or NBA team staff living in the Bubble once cleared from quarantine.

CONCLUSIONS

Drivers of success included the requirement for players and team staff to reside and remain on campus, well-trained compliance monitors, unified communication, layers of protection between teams and the outside, activation of high-quality laboratory diagnostics, and available mental health services. An emphasis on data management, evidence-based decision-making, and the willingness to evolve protocols were instrumental to successful operations. These lessons hold broad applicability for future pandemic preparedness efforts.

Tactical Considerations for Designing Real-World Studies: Fit-for-Purpose Designs That Bridge Research and Practice

Real-world evidence (RWE) is being used to provide information on diverse groups of patients who may be highly impacted by disease but are not typically studied in traditional randomized clinical trials (RCT) and to obtain insights from everyday care settings and real-world adherence to inform clinical practice. RWE is derived from so-called real-world data (RWD), ie, information generated by clinicians in the course of everyday patient care, and is sometimes coupled with systematic input from patients in the form of patient-reported outcomes or from wearable biosensors. Studies using RWD are conducted to evaluate how well medical interventions, services, and diagnostics perform under conditions of real-world use, and may include long-term follow-up. Here, we describe the main types of studies used to generate RWE and offer pointers for clinicians interested in study design and execution. Our tactical guidance addresses (1) opportunistic study designs, (2) considerations about representativeness of study participants, (3) expectations for transparency about data provenance, handling and quality assessments, and (4) considerations for strengthening studies using record linkage and/or randomization in pragmatic clinical trials. We also discuss likely sources of bias and suggest mitigation strategies. We see a future where clinical records - patient-generated data and other RWD - are brought together and harnessed by robust study design with efficient data capture and strong data curation. Traditional RCT will remain the mainstay of drug development, but RWE will play a growing role in clinical, regulatory, and payer decision-making. The most meaningful RWE will come from collaboration with astute clinicians with deep practice experience and questioning minds working closely with patients and researchers experienced in the development of RWE.

Factors associated with antibody titer levels among an occupational cohort of fully vaccinated individuals and subsequent risk of COVID-19 infection: A cohort study

This study (1) determined the association of time since initial vaccine regimen, booster dose receipt, and COVID-19 history with antibody titer, as well as change in titer levels over a defined period, and (2) determined risk of COVID-19 associated with low titer levels. This observational study used data from staff participating in the National Football League COVID-19 Monitoring Program. A cohort of staff consented to antibody-focused sub-study, during which detailed longitudinal data were collected. Among all staff in the program who received antibody testing, COVID-19 incidence following antibody testing was determined. Five hundred eighty-six sub-study participants completed initial antibody testing; 80% (469) completed follow-up testing 50-101 days later. Among 389 individuals who were not boosted at initial testing, the odds of titer < 1000 AU/mL (vs. ≥1000 AU/mL) increased 44% (odds ratio [OR] = 1.44, 95% confidence interval [CI]: 1.18-1.75) for every 30 days since final dose. Among 126 participants boosted before initial testing with no COVID-19 history, 125 (99%) had a value > 2500 AU/ml; 86 (96%) of 90 tested at follow-up and did not develop COVID-19 in the interim remained at that value. One thousand fifty-seven fully vaccinated (330 [29%] boosted at antibody test) individuals participating in the monitoring program were followed to determine COVID-19 status. Individuals with titer value < 1000 AU/mL had twice the risk of COVID-19 as those with >2500 AU/mL (HR = 2.02, 95% CI: 1.28-3.18). Antibody levels decrease postvaccination; boosting increases titer values. While antibody level is not a clear proxy for infection immunity, lower titer values are associated with higher COVID-19 incidence, suggesting increased protection from boosters.

Cognitive and other neuropsychiatric symptoms in COVID-19: analysis of person-generated longitudinal health data from a community-based registry

OBJECTIVE

To describe cognitive symptoms in people not hospitalised at study enrolment for SARS-CoV-2 infection and associated demographics, medical history, other neuropsychiatric symptoms and SARS-CoV-2 vaccination.

DESIGN

Longitudinal observational study.

SETTING

Direct-to-participant registry with community-based recruitment via email and social media including Google, Facebook and Reddit, targeting adult US residents. Demographics, medical history, COVID-19-like symptoms, tests and vaccinations were collected through enrolment and follow-up surveys.

PARTICIPANTS

Participants who reported positive COVID-19 test results between 15 December 2020 and 13 December 2021. Those with cognitive symptoms were compared with those not reporting such symptoms.

MAIN OUTCOME MEASURE

Self-reported cognitive symptoms (defined as 'feeling disoriented or having trouble thinking' from listed options or related written-in symptoms) RESULTS: Of 3908 participants with a positive COVID-19 test result, 1014 (25.9%) reported cognitive symptoms at any time point during enrolment or follow-up, with approximately half reporting moderate/severe symptoms. Cognitive symptoms were associated with other neuropsychiatric symptoms, including dysgeusia, anosmia, trouble waking up, insomnia, headache, anxiety and depression. In multivariate analyses, female sex (OR, 95% CI): 1.7 (1.3 to 2.2), age (40-49 years (OR: 1.5 (1.2-1.9) compared with 18-29 years), history of autoimmune disease (OR: 1.5 (1.2-2.1)), lung disease (OR: 1.7 (1.3-2.2)) and depression (OR: 1.4 (1.1-1.7)) were associated with cognitive symptoms. Conversely, black race (OR: 0.6 (0.5-0.9)) and COVID-19 vaccination before infection (OR: 0.6 (0.4-0.7)) were associated with reduced occurrence of cognitive symptoms.

CONCLUSIONS

In this study, cognitive symptoms among COVID-19-positive participants were associated with female gender, age, autoimmune disorders, lung disease and depression. Vaccination and black race were associated with lower occurrence of cognitive symptoms. A constellation of neuropsychiatric and psychological symptoms occurred with cognitive symptoms. Our findings suggest COVID-19's full health and economic burden may be underestimated.

TRIAL REGISTRATION NUMBER

NCT04368065.

The Effect of Probable COVID-19 Infection on the National Football League Players’ Performance and Endurance During the 2020 Season

Objective The objective of this study was to assess whether the National Football League (NFL) players with probable coronavirus disease 2019 (COVID-19) during the 2020 season experienced a decline in athletic performance and endurance. Methods All players who were listed on the NFL's COVID-19 Injury Reserve (COVID-IR) list were screened for inclusion. Players were included in the study if they had spent ≥10 days on the COVID-19 IR list (which indicated a positive PCR test based on the NFL COVID-19 policies), had played in at least two games before and after going on the IR list, and primarily played an offensive or defensive position. The mean number of snaps played per game and Pro Football Focus (PFF) score per game were collected for each athlete, which served as surrogate measures of endurance and performance, respectively. The results were analyzed with players grouped by position, and then all players grouped as a whole. Within-group comparisons were performed via t-tests. Results A total of 78 players met the criteria for inclusion in the study. The overall mean PFF score pre-COVID-19 infection was 62.15 (SD: 6.93), while it was 61.73 (SD: 7.42) post-COVID-19 infection, showing a decrease of 0.42 after infection (n=78, p=0.33). The mean number of snaps played per game pre-COVID-19 infection was 38.99 (SD: 16.46) while it was 38.10 (SD: 17.05) post-COVID-19 infection, showing a decrease of 0.89 after infection (n=78, p=0.30). When grouped by position, statistically significant differences were seen with Defensive Backs' mean snaps played per game decreasing by 18.30 (n=6, p=0.03) and Defensive Linemen's mean PFF score decreasing by 3.77 points (n=21, p=0.03). Conclusion Based on our findings, COVID-19 infection negatively impacted endurance in Defensive Backs, and performance in Defensive Linemen. However, there was inconclusive evidence to show whether COVID-19 infection negatively impacted other positions when analyzed separately or all positions when analyzed together. Further studies with more participants are needed to fully assess the effects of COVID-19 on performance and endurance in elite athletes.

Evaluating the value of anti-SARS-CoV-2 antibody detection and neutralizing responses with euvirus: A population of 10776 close contacts in the epidemic of Fujian

BACKGROUND

Nucleic acid detection represents limitations due to its false-negative rate and technical complexity in the COVID-19 pandemic. Anti-severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibody tests are widely spread all over the world presently. However, there is no report on the effectiveness of anti-SARS-CoV-2 antibody testing methods in China.

METHODS

We gathered 10776 serum samples from close contacts of the SARS-CoV-2 infections in Fujian of China and used 2 chemiluminescence immunoassays (Wantai Bio., Yahuilong Bio.) and 2 lateral flow immunoassays (Lizhu Bio. and Dongfang Bio.) to perform the anti-SARS-CoV-2 antibody tests in China.

RESULTS

The 4 antibody tests have great diagnostic value for infected or uninfected, especially in the neutralizing antibodies tests, the AUC can reach 0.939 (Wantai Bio.) and 0.916 (Yahuilong Bio.). Furthermore, we used pseudoviruses and euvirus neutralization assay to validate the effectiveness of these antibody test, the results of pseudoviruses neutralization assay or euvirus neutralization assay shows a considerable correlation with the 4 antibody detection respectively, particularly in euvirus neutralization assay, neutralizing antibodies detected by Wantai Bio. or Yahuilong Bio., the correlation can get the level of 0.93 or 0.82.

CONCLUSIONS

The findings of this study demonstrate that the detections of antibodies have profound value in the diagnosis of COVID-19.

Risks, Epidemics, and Prevention Measures of Infectious Diseases in Major Sports Events: Scoping Review

BACKGROUND

Major sports events are the focus of the world. However, the gathering of crowds during these events creates huge risks of infectious diseases transmission, posing a significant public health threat.

OBJECTIVE

The aim of this study was to systematically review the epidemiological characteristics and prevention measures of infectious diseases at major sports events.

METHODS

The procedure of this scoping review followed Arksey and O'Malley's five-step methodological framework. Electronic databases, including PubMed, Web of Science, Scopus, and Embase, were searched systematically. The general information (ie, publication year, study type) of each study, sports events' features (ie, date and host location), infectious diseases' epidemiological characteristics (ie, epidemics, risk factors), prevention measures, and surveillance paradigm were extracted, categorized, and summarized.

RESULTS

A total of 24,460 articles were retrieved from the databases and 358 studies were included in the final data synthesis based on selection criteria. A rapid growth of studies was found over recent years. The number of studies investigating epidemics and risk factors for sports events increased from 16/254 (6.3%) before 2000 to 201/254 (79.1%) after 2010. Studies focusing on prevention measures of infectious diseases accounted for 85.0% (238/280) of the articles published after 2010. A variety of infectious diseases have been reported, including respiratory tract infection, gastrointestinal infection, vector-borne infection, blood-borne infection, and water-contact infection. Among them, respiratory tract infections were the most concerning diseases (250/358, 69.8%). Besides some routine prevention measures targeted at risk factors of different diseases, strengthening surveillance was highlighted in the literature. The surveillance system appeared to have gone through three stages of development, including manual archiving, network-based systems, and automated intelligent platforms.

CONCLUSIONS

This critical summary and collation of previous empirical evidence is meaningful to provide references for holding major sports events. It is essential to improve the surveillance techniques for timely detection of the emergence of epidemics and to improve risk perception in future practice.

Rapid, point-of-care antigen tests for diagnosis of SARS-CoV-2 infection

BACKGROUND

Accurate rapid diagnostic tests for SARS-CoV-2 infection would be a useful tool to help manage the COVID-19 pandemic. Testing strategies that use rapid antigen tests to detect current infection have the potential to increase access to testing, speed detection of infection, and inform clinical and public health management decisions to reduce transmission. This is the second update of this review, which was first published in 2020.

OBJECTIVES

To assess the diagnostic accuracy of rapid, point-of-care antigen tests for diagnosis of SARS-CoV-2 infection. We consider accuracy separately in symptomatic and asymptomatic population groups. Sources of heterogeneity investigated included setting and indication for testing, assay format, sample site, viral load, age, timing of test, and study design.

SEARCH METHODS

We searched the COVID-19 Open Access Project living evidence database from the University of Bern (which includes daily updates from PubMed and Embase and preprints from medRxiv and bioRxiv) on 08 March 2021. We included independent evaluations from national reference laboratories, FIND and the Diagnostics Global Health website. We did not apply language restrictions.

SELECTION CRITERIA

We included studies of people with either suspected SARS-CoV-2 infection, known SARS-CoV-2 infection or known absence of infection, or those who were being screened for infection. We included test accuracy studies of any design that evaluated commercially produced, rapid antigen tests. We included evaluations of single applications of a test (one test result reported per person) and evaluations of serial testing (repeated antigen testing over time). Reference standards for presence or absence of infection were any laboratory-based molecular test (primarily reverse transcription polymerase chain reaction (RT-PCR)) or pre-pandemic respiratory sample.

DATA COLLECTION AND ANALYSIS

We used standard screening procedures with three people. Two people independently carried out quality assessment (using the QUADAS-2 tool) and extracted study results. Other study characteristics were extracted by one review author and checked by a second. We present sensitivity and specificity with 95% confidence intervals (CIs) for each test, and pooled data using the bivariate model. We investigated heterogeneity by including indicator variables in the random-effects logistic regression models. We tabulated results by test manufacturer and compliance with manufacturer instructions for use and according to symptom status.

MAIN RESULTS

We included 155 study cohorts (described in 166 study reports, with 24 as preprints). The main results relate to 152 evaluations of single test applications including 100,462 unique samples (16,822 with confirmed SARS-CoV-2). Studies were mainly conducted in Europe (101/152, 66%), and evaluated 49 different commercial antigen assays. Only 23 studies compared two or more brands of test. Risk of bias was high because of participant selection (40, 26%); interpretation of the index test (6, 4%); weaknesses in the reference standard for absence of infection (119, 78%); and participant flow and timing 41 (27%). Characteristics of participants (45, 30%) and index test delivery (47, 31%) differed from the way in which and in whom the test was intended to be used. Nearly all studies (91%) used a single RT-PCR result to define presence or absence of infection. The 152 studies of single test applications reported 228 evaluations of antigen tests. Estimates of sensitivity varied considerably between studies, with consistently high specificities. Average sensitivity was higher in symptomatic (73.0%, 95% CI 69.3% to 76.4%; 109 evaluations; 50,574 samples, 11,662 cases) compared to asymptomatic participants (54.7%, 95% CI 47.7% to 61.6%; 50 evaluations; 40,956 samples, 2641 cases). Average sensitivity was higher in the first week after symptom onset (80.9%, 95% CI 76.9% to 84.4%; 30 evaluations, 2408 cases) than in the second week of symptoms (53.8%, 95% CI 48.0% to 59.6%; 40 evaluations, 1119 cases). For those who were asymptomatic at the time of testing, sensitivity was higher when an epidemiological exposure to SARS-CoV-2 was suspected (64.3%, 95% CI 54.6% to 73.0%; 16 evaluations; 7677 samples, 703 cases) compared to where COVID-19 testing was reported to be widely available to anyone on presentation for testing (49.6%, 95% CI 42.1% to 57.1%; 26 evaluations; 31,904 samples, 1758 cases). Average specificity was similarly high for symptomatic (99.1%) or asymptomatic (99.7%) participants. We observed a steady decline in summary sensitivities as measures of sample viral load decreased. Sensitivity varied between brands. When tests were used according to manufacturer instructions, average sensitivities by brand ranged from 34.3% to 91.3% in symptomatic participants (20 assays with eligible data) and from 28.6% to 77.8% for asymptomatic participants (12 assays). For symptomatic participants, summary sensitivities for seven assays were 80% or more (meeting acceptable criteria set by the World Health Organization (WHO)). The WHO acceptable performance criterion of 97% specificity was met by 17 of 20 assays when tests were used according to manufacturer instructions, 12 of which demonstrated specificities above 99%. For asymptomatic participants the sensitivities of only two assays approached but did not meet WHO acceptable performance standards in one study each; specificities for asymptomatic participants were in a similar range to those observed for symptomatic people. At 5% prevalence using summary data in symptomatic people during the first week after symptom onset, the positive predictive value (PPV) of 89% means that 1 in 10 positive results will be a false positive, and around 1 in 5 cases will be missed. At 0.5% prevalence using summary data for asymptomatic people, where testing was widely available and where epidemiological exposure to COVID-19 was suspected, resulting PPVs would be 38% to 52%, meaning that between 2 in 5 and 1 in 2 positive results will be false positives, and between 1 in 2 and 1 in 3 cases will be missed.

AUTHORS' CONCLUSIONS

Antigen tests vary in sensitivity. In people with signs and symptoms of COVID-19, sensitivities are highest in the first week of illness when viral loads are higher. Assays that meet appropriate performance standards, such as those set by WHO, could replace laboratory-based RT-PCR when immediate decisions about patient care must be made, or where RT-PCR cannot be delivered in a timely manner. However, they are more suitable for use as triage to RT-PCR testing. The variable sensitivity of antigen tests means that people who test negative may still be infected. Many commercially available rapid antigen tests have not been evaluated in independent validation studies. Evidence for testing in asymptomatic cohorts has increased, however sensitivity is lower and there is a paucity of evidence for testing in different settings. Questions remain about the use of antigen test-based repeat testing strategies. Further research is needed to evaluate the effectiveness of screening programmes at reducing transmission of infection, whether mass screening or targeted approaches including schools, healthcare setting and traveller screening.

Clinical Accuracy of Instrument-Read SARS-CoV-2 Antigen Rapid Diagnostic Tests (Ag-IRRDTs)

This systematic review (PROSPERO registration number: CRD42021282476) aims to collect and analyse current evidence on real-world performance based on clinical accuracy of instrument-read rapid antigen diagnostic tests (Ag-IRRDTs) for SARS-CoV-2 identification. We used PRISMA Checklist and searched databases (PubMed, Web of Science Core Collection and FIND) for publications evaluating the accuracy of SARS-CoV-2 Ag-IRRDTs as of 30 September 2021, and included 40 independent clinical studies resulting in 48 Ag-IRRDT datasets with 137,770 samples. Across all datasets, pooled Ag-IRRDT sensitivity was 67.1% (95% CI: 65.9%-68.3%) and specificity was 99.4% with a tight CI. Pooled sensitivity and specificity of SARS-CoV-2 Ag-IRRDTs did not demonstrate a significant superiority over SARS-CoV-2 rapid antigen tests which do not require a reader instrument, even in the case where surveillance and screening datasets were excluded from the analysis. Nevertheless, they provide connectivity advantages and remove operator interface (in results-reading) issues. The lower sensitivity of certain brands of Ag-IRRDTs can be overcome in high prevalence areas with high frequency of testing. New SARS-CoV-2 variants are major concern for current and future diagnostic performance of these tests.

Effectiveness and Use of RT‐PCR Point of Care Testing in a Large‐Scale COVID ‐19 Surveillance System

Background

Rapid COVID‐19 testing platforms can identify infected individuals at the point of care (POC), allowing immediate isolation of infected individuals and reducing the risk of transmission. While lab‐based nucleic acid amplification testing (NAAT) is often considered the gold standard to detect SARS‐CoV‐2 in the community, results typically take 2–7 days to return, rendering POC testing a critical diagnostic tool for infection control. The National Football League (NFL) and NFL Players Association deployed a new POC testing strategy using a newly available reverse transcriptase polymerase chain reaction (RT‐PCR) rapid test during the 2020 season, and evaluated diagnostic effectiveness compared to other available devices using real‐world population surveillance data.

Methods

RT‐PCR POC test results were compared to NAAT results from same‐day samples by calculation of positive and negative concordance. Sensitivity analyses were performed for three subgroups: (1) individuals symptomatic at time of positive test; (2) individuals tested during the pilot phase of rollout; and (3) individuals tested daily.

Results

Among 4989 same‐day POC/NAAT pairs, 4957 (99.4%) were concordant, with 93.1% positive concordance and 99.6% negative concordance. Based on adjudicated case status, the false negative rate was 0.2% and false positive rate was 2.9%. In 43 instances, the immediate turnaround of results by POC allowed isolation of infected individuals 1 day sooner than lab‐based testing. Positive/negative concordance in sensitivity analyses were relatively stable.

Conclusion

RT‐PCR POC testing provided timely results that were highly concordant with lab‐based NAAT in population surveillance. Expanded use of effective RT‐PCR POC can enable rapid isolation of infected individuals and reduce COVID‐19 infection in the community.

Results from a Test-to-Release from Isolation Strategy Among Fully Vaccinated National Football League Players and Staff Members with COVID-19 - United States, December 14-19, 2021

During December 2021, the United States experienced a surge in COVID-19 cases, coinciding with predominance of the SARS-CoV-2 B.1.1.529 (Omicron) variant (1). During this surge, the National Football League (NFL) and NFL Players Association (NFLPA) adjusted their protocols for test-to-release from COVID-19 isolation on December 16, 2021, based on analytic assessments of their 2021 test-to-release data. Fully vaccinated* persons with COVID-19 were permitted to return to work once they were asymptomatic or fever-free and experiencing improving symptoms for ≥24 hours, and after two negative or high cycle-threshold (Ct) results (Ct≥35) from either of two reverse transcription-polymerase chain reaction (RT-PCR) tests^† (2). This report describes data from NFL's SARS-CoV-2 testing program (3) and time to first negative or Ct≥35 result based on serial COVID-19 patient testing during isolation. Among this occupational cohort of 173 fully vaccinated adults with confirmed COVID-19 during December 14-19, 2021, a period of Omicron variant predominance, 46% received negative test results or had a subsequent RT-PCR test result with a Ct≥35 by day 6 postdiagnosis (i.e., concluding 5 days of isolation) and 84% before day 10. The proportion of persons with positive test results decreased with time, with approximately one half receiving positive RT-PCR test results after postdiagnosis day 5. Although this test result does not necessarily mean these persons are infectious (RT-PCR tests might continue to return positive results long after an initial positive result) (4), these findings indicate that persons with COVID-19 should continue taking precautions, including correct and consistent mask use, for a full 10 days after symptom onset or initial positive test result if they are asymptomatic.

Anatomy of an American football game: Player-to-player contact before, during and after an NFL game in context of the 2020 COVID-19 pandemic

OBJECTIVES

To quantify levels of potential exposure to SARS-CoV-2 surrounding a typical professional American football game, with a focus on interactions on-field between teammates and opposing players before, during, and immediately after competition.

METHODS

We examined across-Club consecutive interactions ≥2 minutes within 6 feet [1.8 meters] between athletes on opposing Clubs for all 2020 NFL regular season games (n = 256). Cumulative interaction was measured for a representative subset (n = 119; 46%) of games. Wearable proximity tracking devices (Kinexon) were used to measure distance and duration of interactions; these data were combined with game schedule and Club rosters for analyses. Frequency and per-game mean, median, interquartile range for consecutive interactions ≥2/≥5 minutes and cumulative interactions ≥5/≥15 were described overall and stratified by pre-game, in-game, and post-game.

RESULTS

Of the 1964 distinct player-to-opponent contacts ≥2 minutes in NFL regular season games, the majority (n = 1,699; 87%) were fewer than 5 minutes in consecutive length. Among the mean 7.7 distinct contacts ≥2 minutes with opponents each game (median = 4; IQR = 2, 8), very few were ≥5 consecutive minutes at any point (mean = 1.0; median = 0; IQR = 0, 0). Most (n = 849; 43.2%) distinct contacts were pre-game, 546 (27.8%) were during competition, and 569 (29%) were post-game. In games where cumulative interactions were analyzed, there was an average of 17.1 player/opponent interactions with cumulative exposure ≥5 minutes (median = 12; IQR = 4, 30), almost all of which occurred during competition.

CONCLUSION

There is limited and short contact between and among competing players in professional American football. In the setting of infectious disease such as the COVID-19 pandemic, a robust prevention program integrating masking, distancing, hygiene, and ventilation when off-field can be created to minimize on- and off-field exposures, which effectively reduces transmission risk in outdoors and/or well-ventilated stadium settings.

Diagnostic usefulness of subgenomic RNA detection of viable SARS-CoV-2 in patients with COVID-19

Objectives

The development of a rapid diagnostic test for viable SARS-CoV-2 is important for infection control. Real-time RT-PCR assays detect non-viable virus, and cell culture differentiates viable virus but it takes several weeks and is labour-intensive. Subgenomic RNAs may reflect replication-competent virus. We therefore evaluated the usefulness of subgenomic RNAs for diagnosing viable SARS-CoV-2 in patients with COVID-19.

Methods

Patients with various severities of confirmed COVID-19 were enrolled at a tertiary hospital between February and December 2020. RT-PCR assay results for genomic and subgenomic RNA of SARS-CoV-2 from nasopharyngeal swab, sputum and saliva specimens were compared with cell culture results.

Results

A total 189 specimens from 20 COVID-19 patients were tested in genomic and subgenomic PCR assays and cultured on Vero cells. Of these 189 samples, 62 (33%) gave positive culture results, 93 (49%) negative results and the remaining 34 (18%) indeterminate results. Compared with cell culture results, the sensitivities of genomic RNA and subgenomic RNA of the N and S genes were comparable at 100%, but the specificity of subgenomic RNA (N, 65% and S, 68%) was higher than that of genomic RNA (N, 23% and S, 17%, p < 0.001). The mean durations of positive culture and subgenomic RNA were 11.39 ± 10.34 and 13.75 ± 11.22 days after symptom onset (p 0.437), respectively, while that of genomic RNA was 22.85 ± 11.83 days after symptom onset (p < 0.001).

Discussion

Our comparison of subgenomic RNA detection with symptom duration and SARS-CoV-2 culture positivity provides a significant advancement on the transmissibility-based approach beyond the detection of SARS-CoV-2 genomic RNA, and warrants further studies on the development of better diagnostic strategy.

Association between household exposure and cycle threshold in COVID-19 infected health care workers

OBJECTIVE

Household SARS-COV-2 contact constitutes a high-risk exposure for health care workers (HCWs). Cycle threshold (Ct) of reverse transcriptase-polymerase chain reaction testing provides an estimate of COVID-19 viral load, which can inform clinical and workplace management. We assessed whether Ct values differed between HCWs with COVID-19 with and without household exposure.

METHODS

We analyzed HCW COVID-19 cases whose Ct data could be compared. We defined low Ct at a cut-point approximating a viral load of 4.6 × 106 copies per ml. Logistic regression tested the association of household exposure and symptoms at diagnosis with a low Ct value.

RESULTS

Of 77 HCWs with COVID-19, 20 were household exposures cases and 34 were symptomatic at testing (7 were both household-exposed and symptomatic at testing). Among household exposures, 9 of 20 (45%) manifested lower Ct values compared to 14 of 57 (25%) for all others. In a bivariate model, household exposure was not statistically associated with lower Ct (Odds Ratio [OR] 1.20; 95% Confidence Interval [CI] 0.97-1.51). In multivariable modelling both household exposure (OR] 1.3; 95% CI 1.03-1.6) and symptoms at diagnosis (OR 1.4; 95% CI 1.15-1.7) were associated with a low Ct value.

DISCUSSION

Household exposure in HCWs with newly diagnosed COVID-19 was associated with lower Ct values, consistent with a higher viral load, supporting the hypothesis that contracting COVID-19 in that manner leads to a greater viral inoculum.