Schmitz, Bradley

Bradley Schmitz is a Visiting Researcher at the Yuma Center of Excellence for Desert Agriculture (YCEDA). He received his Ph.D. in Environmental...

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About Schmitz, Bradley

Bradley Schmitz is a Visiting Researcher at the Yuma Center of Excellence for Desert Agriculture (YCEDA). He received his Ph.D. in Environmental Microbiology from the University of Arizona and previously held two postdoc positions at the National University of Singapore and Johns Hopkins University. Bradley's research focuses on the intersection between water and public health. He is currently leading WBE efforts in Arizona - direclty informing public health officials, hospital staff, and state/county admin to trigger preparedness and response actions to prevent the spread of COVID-19.

Schmitz, Bradley

Titles from this speaker

Description: COVID-19 containment on a college campus via wastewater-based epidemiology, targeted...

COVID-19 containment on a college campus via wastewater-based epidemiology, targeted clinical testing and an intervention

Abstract

Background: Wastewater-based epidemiology (WBE) has potential as an early-warning tool for determining the presence of COVID-19 in a community. The University of Arizona (UArizona) utilized WBE paired with clinical testing as a surveillance tool to monitor the UArizona community for SARS-CoV-2 in near real-time, as students re-entered campus in the fall. Wastewater results were utilized as a leading indicator to support public health decisions. Wastewater surveillance of student dormitories was used as the foundation of a strategy to contain potential outbreaks of disease following student re-entry onto campus for the Fall semester of 2020. Upon positive detection of viral RNA in wastewater samples, clinical testing was conducted on every individual living in the dorm. Infected individuals, asymptomatic and/or asymptomatic, were identified and relocated into an isolation dorm to prevent further disease transmission. Testing wastewater also allowed for evaluation of the effects of an intervention introduced onto the university community, mid-semester, namely a 'shelter in place' order imposed on the students. This presentation describes the community-wide protocols, testing plans, interventions, and results that took place to prevent over 90 outbreaks throughout the academic semester. The success of this study was featured in hundreds of international news outlets throughout Fall 2020. This study also provided the blueprint for numerous universities across the nation that are utilizing similar techniques pairing wastewater surveillance and targeted clinical testing to prevent the spread of COVID-19 amongst the campus community. Methods: Upon arriving to campus prior to the academic year, every individual was required to report to a designated COVID-19 testing site and undergo an anterior nasal swab for antigen testing. Individuals were kept on-site until tests results were noted. If a person had a positive COVID-19 test, they were required to isolate for a minimum of 10 days (at home or in a designated isolation dorm) from the onset of symptoms or from the date the sample was taken, per guidelines from the United States Center for Disease Control and Prevention (CDC). Therefore, all individuals on campus at the start of the semester were assumed to be free from SARS-CoV-2 infection. UArizona administration assembled a Task Force and Campus Re-Entry Working Groups to prepare for students' safe return to campus and classrooms. The WBE expert team hypothesized that surveillance of defined communities in dorms would provide an effective means for identifying new cases of COVID-19 since: 1) each dorm contained a known population; 2) dorm students provide a representation of the overall status of campus health; 3) wastewater samples could be collected from individual buildings; and 4) actionable public health responses could be initiated in the event of positive wastewater detection. Therefore, the university created a plan for wastewater surveillance of student dorms throughout the academic year. Samples were collected twice-per-week from manholes downstream from 13 dorms prior to convergence or mixing with other sewer lines, resulting in samples specific to individual buildings with defined communities. Results and Discussion: A baseline survey of SARS-CoV-2 RNA in wastewater was conducted prior to the fall semester via wastewater sample collection from multiple dorms between August 18-20, 2020, when some students had already returned for fall semester. No SARS-CoV-2 RNA was detected in these samples, which corroborated with the requirement that all students were determined negative prior to dorm entry. Only a few days after classes started in-person instruction, the first positive wastewater result was detected from Dorm A. This triggered immediate UA Task Force meeting, which supported additional wastewater testing to confirm results and mandatory clinical testing of all dorm residents. Two clinical tests for COVID-19 diagnosis were performed on all residents: antigen via anterior nasal swab and RT-PCR via nasopharyngeal swab samples. Data was de-duplicated when both tests resulted in positive. Figure 1 provides a timeline for the public health response actions and events described throughout the study. The next day, five wastewater samples collected five-minutes apart confirmed identical concentrations of SARS-CoV-2 RNA detected the day prior (Table 1). This validated the presence for SARS-CoV-2 in the wastewater samples that were representative of the resident population living in the dorm. Simultaneously, 270 antigen tests and 260 PCR tests were conducted on-site at Dorm A among the 311 total residents (Table 2). Antigen testing identified one positive individual (Person A) despite demonstrating no symptoms. The other 269 antigen tests were negative. An additional individual reported experiencing symptoms (Person B) and tested positive via an antigen test. Person A and Person B were immediately relocated into an isolation facility to prevent viral transmission. Over the next two days, antigen tests (34 individuals) and PCR tests (24 individuals) were conducted among individuals that were not originally available for testing. All clinical tests were negative (Table 2), as were corresponding wastewater samples, indicating that the source(s) for SARS-CoV-2 had likely been removed from the dorm. Only two days later, wastewater results returned to positive, but at very low concentrations. Clinical PCR tests confirmed another infected individual (Person C). Interestingly, this person previously had inconclusive results during the original testing in response to the first wastewater positive. It is possible that Person C was not shedding virus or had low viral shedding during that time, likely due to early stages of infection. Regardless, Person C was removed from the dorm and virus RNA was no longer detected in wastewater. Importantly, another resident (Person D) returned to the dorm the same day wastewater was positive, after following isolation protocols. The successful use of WBE coupled with targeted clinical testing in Dorm A provided confidence for an early-warning system that can avert COVID-19 outbreaks. Therefore, this program was expanded to monitor 13 dorms during the course of the semester. Specifically, 91 out of 111 (82.0% positive predictive value) positive wastewater samples successfully provided a warning that at least one individual living in the dorm was positive with a SARS-CoV-2 infection (Table 3); results were confirmed via a positive clinical test within 4 days of the wastewater sample. This corroborates with a recent report that suggests peak shedding occurs within the first week of illness (Cevik et al., 2020). Also, 185 out of 208 (88.9% negative predictive value) negative wastewater samples concurred with no new positive individuals on dormitory screenings (Table 3). Only 43 out of 319 total wastewater samples were discordant with results from clinical tests (Table 3). Positive wastewater samples not followed with positive clinical tests could be due to infected visitors and/or on few occasions less than 100% of the dorm residents tested. At the beginning of the semester there were no infections in the monitored dorms. Following campus re-entry, there were clusters of cases during the first 18 days of the semester. This was followed by a dramatic spike in cases beginning September 14, likely due to student behavior around the Labor Day holiday on September 7. Infections resulting from the holiday-related activities would be reflected in new cases being detected likely about five days thereafter (Lauer et al., 2020). Following the spike, the president of UArizona, endorsed a 'shelter in place' policy imposed by Pima County on September 15-29, 2020. The effectiveness of this intervention resulted in a dramatic decrease in the number of daily new-reported cases by September 21 (Figure 2). The decrease in new cases was associated with decreased viral concentrations in the wastewater over this period. Following this intervention, case counts remained remarkably low, and often zero for the rest of September, October, and into November. The vast majority of students left campus the Friday before Thanksgiving, November 20, and did not return to campus. Therefore, there are no WBE results to report for the month of December as the final weeks of courses and exams were conducted remotely online. Concluding Remarks: The combined strategy of utilizing WBE coupled with targeted clinical testing was critical in COVID-19 containment. WBE strategies averted potential transmission from numerous students, which allowed the university to remain open. The data from this study provide evidence that validate WBE as an important tool that can and should be used in tandem with diagnostics and infection prevention practices to intervene in COVID-19 transmission, and ultimately save lives.

The following conference paper was presented at the Public Health and Water Conference & Wastewater Disease Surveillance Summit in Cincinnati, OH, March 21-24, 2022.

SpeakerSchmitz, Bradley

Presentation time

11:05:00

11:25:00

Session time

10:45:00

11:45:00

SessionLocalized Case Studies

Session number9

Session locationDuke Energy Convention Center, Cincinnati, Ohio

TopicCollection Systems, Data Management, Research, wastewater

Author(s)

Schmitz, Bradley

Author(s)B. Schmitz1; W. Betancourt2; I. Pepper3; S. Prasek4; G. Innes5; S. Sherchan6

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Mar 2022

DOI10.2175/193864718825158288

Volume / Issue

Content sourcePublic Health and Water Conference

Word count16

Description: WEF-PHC22-Proceedings cover-2400x3200

Enumerating asymptomatic COVID-19 cases and estimating SARS-CoV-2 fecal shedding rates via wastewater-based epidemiology

Abstract

Background: Multiple jurisdictions around the world have attempted to quantify the total number of individuals infected with SARS-CoV-2 in the community that excreted the virus into wastewater (Ahmed et al., 2020; Chavarria-Miro et al., 2021; Curtis et al., 2020). Models and predictions have been based on fecal shedding rates derived from limited results that indicated a large variance across a small number of individuals (Wolfel et al., 2020). Furthermore, these fecal shedding rates were extrapolated from the 90th percentile of this limited dataset and used to calculate the number of infected individuals contributing to viral loads in wastewater (Ahmed et al., 2020; Chavarria-Miro et al., 2021; Curtis et al., 2020). However, these estimates are likely to be inaccurate without pairing wastewater results with clinical data. More recently, the University of Arizona (UArizona) used WBE, dovetailed with targeted clinical testing, to prevent COVID-19 outbreaks in student dormitories (dorms) (Betancourt et al., 2021). The current study builds upon the successful public health actions performed at UArizona by aggregating data from positive wastewater samples with number of clinically positive cases to provide estimations for fecal shedding rates amongst infected university students. This also enabled tracking the proportion of symptomatic and asymptomatic individuals that corroborated with wastewater results from defined communities composed of young adults (18-20 years old). This is the first study to determine community-wide fecal shedding rates by directly pairing clinical and wastewater results. Findings from this study may act as a benchmark to assess SARS-CoV-2 prevalence in a population and inform public health prevention and response actions. Methods: In total, 13 student dorms (Dorm A-M) at UArizona main campus were monitored throughout the Fall 2020 Semester (August 17--November 20). Wastewater samples were collected two-times-per-week from sewer manholes specific to each dorm's effluent prior to convergence with other sewer pipelines; thus, all wastewater samples were specific to the defined communities living in each dorm. The total number of residents at each dorm was known (Table 1) and was considered a closed population as visitors were prohibited. Positive detection of SARS-CoV-2 RNA (via the N1 gene region) in wastewater acted as the leading indicator for the presence of SARS-CoV-2 infections within the dorm communities. Results were immediately communicated to the UA Task Force and Campus Re-Entry Working Groups, which planned and conducted clinical testing of residents (Betancourt et al., 2021). Clinical tests for COVID-19 diagnosis were performed via antigen testing from nasal swab samples and RT-PCR from nasopharyngeal swab samples. Individuals with COVID-19 symptoms who sought clinical testing were tested through Campus Health Services (CHS), while non-reporting and asymptomatic cases were tested via targeted clinical testing at dorms with positive wastewater detection through the Test All Test Smart Program (TATS). Individuals that tested positive were removed from the dorm and transferred to another location for isolation. To estimate the number of SARS-CoV-2 infected individuals who contributed to a single positive wastewater sample, a 6-day range of clinical data was considered. Positive clinical cases from the day before, day-of, and four days after sampling were included in the count of infected individuals contributing to viral shedding. The rationale for this approach is: 1) Residual virus-shed from individuals testing positive for COVID-19 the day prior to sampling-may be detected in wastewater the following day. Previous sampling indicates that virus can persist for extended periods of time and be detected even when an estimated 1000 gallons of wastewater has continued to flow through a sewer system (Betancourt et al., 2021). 2) Individuals infected with SARS-CoV-2 may shed virus into wastewater prior to showing symptoms and/or being identified as a clinical case. The viral load of SARS-CoV-2 appears to peak in the upper respiratory tract of infected individuals within the first week of infection (Cevik et al., 2020) and the median incubation period for COVID-19 is estimated to be approximately five days (Lauer et al., 2020). Although infected individuals can shed virus several weeks after infection (Cevik et al., 2020), the 6-day window for calculating shedding rates was appropriate since wastewater testing was performed at least twice per week and all infected individuals that tested positive within the 3-4 day window between samples were removed into isolation prior to the next sampling event. Also, individuals were assumed to be at peak shedding for the first 6 days in which an infected person could be identified via UArizona WBE protocols. The fecal shedding rate of SARS-CoV-2 RNA per gram of feces from an infected individual was enumerated based on known concentrations of viral RNA in positive wastewater samples and the fact that the total numbers of infected individuals contributing to the total virus load in the samples were also known. The fecal shedding rate (FS) defined as genome copies per gram-feces (gc/g-feces) was calculated using Equation 1 based on the N1 gene concentrations. Results and Discussion: This current study examined clinical testing data to determine the abundance of asymptomatic versus symptomatic cases in these defined communities. For all dates in the study period, a total of 711 clinical cases were reported among the 13 unique dorms. Across all dorms, 148 symptomatic cases and 563 asymptomatic cases were reported; thus, 79.2% of SARS-CoV-2 infections were asymptomatic and only 20.8% were symptomatic (Table 2). Positive wastewater samples were aligned with clinical data to extrapolate the fecal shedding rates of SARS-CoV-2 N1 gene. The average N1 shedding rate per infected person was calculated to be 7.30 ± 0.67 log10 gc/g-feces, considering all positive wastewater samples across all dorms (Table 3). Until this research, fecal shedding rate of SARS-CoV-2 from infected individuals had not been well understood. This study successfully enumerated fecal shedding rates in young university students (18-20 years old) which can be used in models for estimating disease prevalence. Our shedding rate figure is an assumed early infection shedding rate estimate because students were identified within the 6-day period and transferred from the dorm into an isolated living quarters. Sensitivity analyses performed in this study suggest that detected RNA concentrations in wastewater samples is the most influential factor for estimating viral shedding rates in infected individuals. Other factors such as demographics of a specific community (i.e., median age) and disease severity may also influence viral shedding rates in feces. Although the approximate shedding rate from this study does not apply for the general population, this project provides a blueprint for conducting further investigations to determine viral shedding rate variance among specific demographics. Our team is currently conducting such analysis on six communities across the USA with median age groups ranging from 27 to 62 years of age (Table 4). Preliminary data suggests that community-wide shedding rates increases with median age groups (Figure 2). Final results and interpretations from this investigation are anticipated by end of 2021 and will be ready to share at the conference. These findings will provide shedding rates based on population demographics, which are essential for building disease prevalence models for specific communities. Lastly, it is important to note that no fecal samples were collected from individual COVID-19 patients directly. Therefore, results in this study are specific to wastewater from defined communities. These data are valuable due to the limited clinical research and evaluations on SARS-CoV-2 fecal shedding rates. Concluding Remarks: This study may have significant implications for public health. The fecal shedding rate of SARS-CoV-2 RNA derived in this study may be incorporated into models to estimate the total number of infections in communities with similar demographics based on wastewater viral concentrations. Knowledge of disease prevalence, especially as a leading indicator, can be used to assist communities in efficient resource allocation to prevent and contain COVID-19 outbreaks. This study also provides further understanding for the total number of cases that are symptomatic versus asymptomatic. Moving forward, the number of reported cases can provide context for estimating the number of cases that were asymptomatic and/or unreported. This, in turn, could have implications for understanding the proportion of individuals that has been exposed to COVID-19 and for understanding progress towards immunity within a community.

The following conference paper was presented at the Public Health and Water Conference & Wastewater Disease Surveillance Summit in Cincinnati, OH, March 21-24, 2022.

SpeakerSchmitz, Bradley

Presentation time

10:35:00

10:55:00

Session time

8:30:00

17:00:00

SessionWastewater Disease Surveillance Summit

Session numberWDSS

Session locationDuke Energy Convention Center, Cincinnati, Ohio

Topicwastewater

Author(s)

Schmitz, Bradley

Author(s)B. Schmitz1; G. Innes2; S. Prasek3; W. Betancourt4; E. Stark5; A. Foster6; A. Abraham7; C. Gerba8; I. Pepper9

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Mar, 2022

DOI10.2175/193864718825158287

Volume / Issue

Content sourcePublic Health and Water Conference

Word count14

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Schmitz, Bradley

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