Relationship of SARS-CoV-2 Antigen and Reverse Transcription PCR Positivity for Viral Cultures.

We assessed the relationship between antigen and reverse transcription PCR (RT-PCR) test positivity and successful virus isolation. We found that antigen test results were more predictive of virus recovery than RT-PCR results. However, virus was isolated from some antigen-negative and RT-PCR‒positive paired specimens, providing support for the Centers for Disease Control and Prevention antigen testing algorithm.

Epidemiologic Characteristics Associated With Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Antigen-Based Test Results, Real-Time Reverse Transcription Polymerase Chain Reaction (rRT-PCR) Cycle Threshold Values, Subgenomic RNA, and Viral Culture Results From University Testing.

BACKGROUND: Real-time reverse transcription polymerase chain reaction (rRT-PCR) and antigen tests are important diagnostics for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Sensitivity of antigen tests has been shown to be lower than that of rRT-PCR; however, data to evaluate epidemiologic characteristics that affect test performance are limited. METHODS: Paired mid-turbinate nasal swabs were collected from university students and staff and tested for SARS-CoV-2 using both Quidel Sofia SARS Antigen Fluorescent Immunoassay (FIA) and rRT-PCR assay. Specimens positive by either rRT-PCR or antigen FIA were placed in viral culture and tested for subgenomic RNA (sgRNA). Logistic regression models were used to evaluate characteristics associated with antigen results, rRT-PCR cycle threshold (Ct) values, sgRNA, and viral culture. RESULTS: Antigen FIA sensitivity was 78.9% and 43.8% among symptomatic and asymptomatic participants, respectively. Among rRT-PCR positive participants, negative antigen results were more likely among asymptomatic participants (odds ratio [OR] 4.6, 95% confidence interval [CI]: 1.3-15.4) and less likely among participants reporting nasal congestion (OR 0.1, 95% CI: .03-.8). rRT-PCR-positive specimens with higher Ct values (OR 0.5, 95% CI: .4-.8) were less likely, and specimens positive for sgRNA (OR 10.2, 95% CI: 1.6-65.0) more likely, to yield positive virus isolation. Antigen testing was >90% positive in specimens with Ct values < 29. Positive predictive value of antigen test for positive viral culture (57.7%) was similar to that of rRT-PCR (59.3%). CONCLUSIONS: SARS-CoV-2 antigen test advantages include low cost, wide availability and rapid turnaround time, making them important screening tests. The performance of antigen tests may vary with patient characteristics, so performance characteristics should be accounted for when designing testing strategies and interpreting results.

Association of Shared Living Spaces and COVID-19 in University Students, Wisconsin, USA, 2020.

We describe characteristics associated with having coronavirus disease (COVID-19) among students residing on a university campus. Of 2,187 students, 528 (24.1%) received a COVID-19 diagnosis during fall semester 2020. Students sharing a bedroom or suite had approximately twice the odds of contracting COVID-19 as those living alone.

Performance of an Antigen-Based Test for Asymptomatic and Symptomatic SARS-CoV-2 Testing at Two University Campuses - Wisconsin, September-October 2020.

Antigen-based tests for SARS-CoV-2, the virus that causes coronavirus disease 2019 (COVID-19), are inexpensive and can return results within 15 minutes (1). Antigen tests have received Food and Drug Administration (FDA) Emergency Use Authorization (EUA) for use in asymptomatic and symptomatic persons within the first 5-12 days after symptom onset (2). These tests have been used at U.S. colleges and universities and other congregate settings (e.g., nursing homes and correctional and detention facilities), where serial testing of asymptomatic persons might facilitate early case identification (3-5). However, test performance data from symptomatic and asymptomatic persons are limited. This investigation evaluated performance of the Sofia SARS Antigen Fluorescent Immunoassay (FIA) (Quidel Corporation) compared with real-time reverse transcription-polymerase chain reaction (RT-PCR) for SARS-CoV-2 detection among asymptomatic and symptomatic persons at two universities in Wisconsin. During September 28-October 9, a total of 1,098 paired nasal swabs were tested using the Sofia SARS Antigen FIA and real-time RT-PCR. Virus culture was attempted on all antigen-positive or real-time RT-PCR-positive specimens. Among 871 (79%) paired swabs from asymptomatic participants, the antigen test sensitivity was 41.2%, specificity was 98.4%, and in this population the estimated positive predictive value (PPV) was 33.3%, and negative predictive value (NPV) was 98.8%. Antigen test performance was improved among 227 (21%) paired swabs from participants who reported one or more symptoms at specimen collection (sensitivity = 80.0%; specificity = 98.9%; PPV = 94.1%; NPV = 95.9%). Virus was isolated from 34 (46.6%) of 73 antigen-positive or real-time RT-PCR-positive nasal swab specimens, including two of 18 that were antigen-negative and real-time RT-PCR-positive (false-negatives). The advantages of antigen tests such as low cost and rapid turnaround might allow for rapid identification of infectious persons. However, these advantages need to be balanced against lower sensitivity and lower PPV, especially among asymptomatic persons. Confirmatory testing with an FDA-authorized nucleic acid amplification test (NAAT), such as RT-PCR, should be considered after negative antigen test results in symptomatic persons, and after positive antigen test results in asymptomatic persons (1).

Factors Influencing Risk for COVID-19 Exposure Among Young Adults Aged 18-23 Years - Winnebago County, Wisconsin, March-July 2020.

On May 13, 2020, the Wisconsin Supreme Court declared the state's Safer at Home Emergency Order (https://evers.wi.gov/Documents/COVID19/EMO28-SaferAtHome.pdf) "unlawful, invalid, and unenforceable,"* thereby increasing opportunities for social and business interactions. By mid-June, Winnebago County,† Wisconsin experienced an increase in the number of infections with SARS-CoV-2, the virus that causes coronavirus disease 2019 (COVID-19), with the largest increase among persons aged 18-23 years (young adults) (1). This age group§ accounts for 12.5% of the population in the county. To identify factors that influence exposure to COVID-19 among young adults in Winnebago County, characteristics of COVID-19 cases and drivers of behaviors in this age group were examined. During March 1-July 18, 2020, 240 young adults received positive SARS-CoV-2 test results, accounting for 32% of all Winnebago County cases. In 30 key informant interviews, most interviewees reported exposure to misinformation, conflicting messages, or opposing views about the need for and effectiveness of masks. Thirteen young adults described social or peer pressure to not wear a mask and perceived severity of disease outcome for themselves as low but high for loved ones at risk. Having low perceived severity of disease outcome might partly explain why, when not in physical contact with loved ones at risk, young adults might attend social gatherings or not wear a mask (2). Exposure to misinformation and unclear messages has been identified as a driver of behavior during an outbreak (3,4), underscoring the importance of providing clear and consistent messages about the need for and effectiveness of masks. In addition, framing communication messages that amplify young adults' responsibility to protect others and target perceived social or peer pressure to not adhere to public health guidance might persuade young adults to adhere to public health guidelines that prevent the spread of COVID-19.

Application of a Serial Antigen-Based Testing Strategy for Severe Acute Respiratory Syndrome Coronavirus 2 and Student Adherence in a University Setting: Wisconsin, October-November 2020.

BACKGROUND: Serial severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) testing has been implemented at institutions of higher education (IHEs) and other settings. Testing strategies can include algorithms specifying confirmatory reverse-transcription polymerase chain reaction (RT-PCR) testing after an antigen test. It is unknown how testing strategies perform detecting SARS-CoV-2, including individual adherence to serial testing requirements. METHODS: Student serial testing adherence was defined as completing ≥80% of weekly tests from October 5, 2020 to November 14, 2020 and evaluated using logistic regression. Medical records were reviewed for all positive antigen test encounters and 10% of daily negative antigen test encounters during October 19-November 30, 2020. Results were used to estimate the proportion of individuals requiring only antigen tests, requiring and completing RT-PCR testing, and associated costs of tests. RESULTS: Two thirds (66.5%; 1166 of 1754) of eligible on-campus students adhered to weekly testing; female students were more adherent (adjusted odds ratio [aOR], 2.07; 95% confidence interval, 1.66-2.59) than male students. Of all antigen test encounters, 11.5% (1409 of 12 305) reported >1 COVID-19 symptoms. Of non-COVID-19-exposed antigen test encounters, 88% (10 386 of 11 769) did not require confirmatory RT-PCR testing. Only 28% (390 of 1387) of testing encounters had an associated recommended confirmatory RT-PCR test performed. We estimated the testing strategy captured 61% (235 of 389) of predicted RT-PCR-positive specimens. CONCLUSIONS: At this IHE, most students voluntarily adhered to serial testing. The majority of antigen test results did not require confirmatory RT-PCR testing, but when required, most students did not obtain it. Including strategies to increase the proportion of individuals obtaining indicated confirmatory testing might improve the testing program's performance.

Antigen Test Performance Among Children and Adults at a SARS-CoV-2 Community Testing Site.

BACKGROUND: Performance characteristics of SARS-CoV-2 antigen tests among children are limited despite the need for point-of-care testing in school and childcare settings. We describe children seeking SARS-CoV-2 testing at a community site and compare antigen test performance to real-time reverse transcription-polymerase chain reaction (RT-PCR) and viral culture. METHODS: Two anterior nasal specimens were self-collected for BinaxNOW antigen and RT-PCR testing, along with demographics, symptoms, and exposure information from individuals ≥5 years at a community testing site. Viral culture was attempted on residual antigen or RT-PCR-positive specimens. Demographic and clinical characteristics, and the performance of SARS-CoV-2 antigen tests, were compared among children (<18 years) and adults. RESULTS: About 1 in 10 included specimens were from children (225/2110); 16.4% (37/225) were RT-PCR-positive. Cycle threshold values were similar among RT-PCR-positive specimens from children and adults (22.5 vs 21.3, P = .46) and among specimens from symptomatic and asymptomatic children (22.5 vs 23.2, P = .39). Sensitivity of antigen test compared to RT-PCR was 73.0% (27/37) among specimens from children and 80.8% (240/297) among specimens from adults; among specimens from children, specificity was 100% (188/188), positive and negative predictive values were 100% (27/27) and 94.9% (188/198), respectively. Virus was isolated from 51.4% (19/37) of RT-PCR-positive pediatric specimens; all 19 had positive antigen test results. CONCLUSIONS: With lower sensitivity relative to RT-PCR, antigen tests may not diagnose all positive COVID-19 cases; however, antigen testing identified children with live SARS-CoV-2 virus.

Syndromic surveillance using regional emergency medicine internet.

STUDY OBJECTIVE: We demonstrate the feasibility and utility of emergency department (ED) syndromic surveillance using a regional emergency medicine Internet application to minimize impact on ED and public health staffing. METHODS: Regional (multi-ED) surveillance was established for 2 periods, one characterized by a high-profile national sports event and the other during an international disease outbreak. Counts of patient visits meeting syndrome criteria and total patient visits were reported daily on the secure regional emergency medicine Internet site and downloaded by public health staff. Trends were analyzed and displayed on the secure Web site. ED participants were surveyed about the acceptability and time cost of the project. RESULTS: In the first ("All Star Game") project, 8 departments reported daily counts for 4 weeks, covering more than 26,000 patient visits. In the second ("severe acute respiratory syndrome" [SARS]) project, an average of 11 departments in the same region reported daily data on febrile respiratory illnesses, travel, and contacts for 10 weeks. Experience with the first project allowed for rapid implementation of the second project during a 3-day period. In both instances, the surveillance efforts were undertaken without the need for extraordinary ED or public health staffing requirements. CONCLUSION: A regional emergency medicine Internet approach permitted rapid implementation of multisite syndromic surveillance without additional staff. Some problems were identified with the first project, related to clinician checklist completion and manual data tabulation and entry. The SARS project addressed these by simplifying data collection and restricting it to triage.

The public health dashboard: a surveillance model for bioterrorism preparedness.

The City of Milwaukee Health Department piloted a short-term, near real-time syndromic surveillance and communication tool by using an existing secure regional Internet infrastructure. Voluntary, active syndromic case reporting by hospital Emergency Departments was combined with other data streams, including clinical laboratory reports of communicable disease, hospital emergency room diversions, ambulance runs, medical examiner reports of unusual or suspicious deaths, poison control and nursing hotline call volumes, and pharmacy over-the-counter sales. These data were aggregated into a "Surveillance Dashboard" format that was used to communicate community syndromic health trends to hospitals, Emergency Departments, and other providers using a secure Internet technology. Emergency Departments at 8 area hospitals reported a total of 314 cases meeting syndromic criteria from 26,888 patient encounters. Participants were satisfied with data entry and communications. All participating Emergency Departments received e-mail and text pager alerts sent by the Milwaukee Health Department. No unexplained findings or suggestions of an early outbreak were reported through syndrome surveillance for the 4-week duration of the project. Similar surveillance and communications systems could provide multiple benefits to Emergency Department workflow and management, as well as to public health and emergency response.