Project names: Sampling for Bioaerosols and surface SARS-CoV-2 on a college campus: A pilot study
Wastewater: MDHHS SARS-CoV-2 Epidemiology – Wastewater Evaluation and Reporting (SEWER) Network
Understanding COVID exposure risks on campus
Investigator(s): Chuanwu Xi (PI), Richard (Rick) Neitzel (Co-I)
Team: Jianfeng Wu, Xin Li, Xin Zhang, Lauren Smith
Source of funding: University of Michigan Provost’s Office, University of Michigan School of Public Health, and the Michigan Department of Health and Human Services
Dates: July 2020 – December 2022
Description:
Background: Evidence was needed on the presence of SARS-CoV-2 in various types of environmental samples and on the estimated transmission risks in non-healthcare settings on campus at the beginning of the COVID pandemic. After the pandemic, we continued the effort with the State of Michigan on wastewater surveillance for other epidemics.
Methods: We collected air and surface samples using wetted wall cyclone bioaerosol samplers and swab kits, respectively, in a longitudinal environmental surveillance program from August 2020 until April 2022 on the University of Michigan Ann Arbor campus. We also coordinated with the City of Ann Arbor and the University to collect wastewater samples from sewage for SARS-CoV-2 and influenza surveillance since 2021. In Dr. Xi’s lab, we used quantitative rRT-PCR for SARS-CoV-2 RNA quantification. The RNA concentrations were used to estimate the probability of infection using quantitative microbial risk assessment modeling and Monte-Carlo simulation. The wastewater samples were analyzed in other ways.
Objectives:
- To quantify the SARS-CoV-2 viral load in the air and on surfaces in publicly accessible non-healthcare environments on a university campus.
- To estimate the probability of infection for people exposed to the virus through inhalation and/or surface contact.
- To inform campus social distancing and cleaning policies in gym, classroom and other public areas.
- To monitor the change of SARS-CoV-2 viral load in the wastewater in relation to reported COVID cases in the area.
- To monitor other viral load in the wastewater as indicators for local epidemics.
Results
Air samples (N=256) and surface samples (N=517) were collected on campus. Positivity rates were low and very similar for both sample types (1.6% and 1.4%, respectively). Correlation analysis showed that the case number on campus was significantly higher in weeks with positive environmental samples than in non-positive weeks (p = 0.001). In simulated scenarios using the viral load found in air and surface samples, we estimated the probability of infection to be about 1 per 100 exposures to contaminated air through inhalation and up to 1 per 100,000 exposures from contaminated surface contact.
Publications:
Zhang, X., Wu, J., Smith, L.M. et al. Monitoring SARS-CoV-2 in air and on surfaces and estimating infection risk in buildings and buses on a university campus. J Expo Sci Environ Epidemiol (2022)
Posters:
“Infection Risk Modeling of SARS-CoV-2 in Air and on Surfaces on a University Campus,” American Industrial Hygiene Association, Nashville, TN, May 2022
Exposure Research Lab 