Agent-based simulations for optimized prevention of the spread of SARS-CoV-2 in nursing homes

Due to its high lethality amongst the elderly, nursing homes are in the eye of the COVID-19 storm. Emerging new test procedures, such as antigen or RT-LAMP tests, might enable us to protect nursing home residents by means of preventive screening strategies. Here, we develop a novel agent-based epidemiological model for the spread of SARS-CoV-2 in nursing homes to identify optimal preventive testing strategies to curb this spread. The model is microscopically calibrated to high-resolution data from actual nursing homes in Austria, including the detailed networks of social contacts of their residents and information on past outbreaks. We find that the effectiveness of preventive screenings depends critically on the timespan between test and test result, the detection threshold of the viral load for the test to give a positive result, and the screening frequencies of residents and employees. Under realistic conditions, we find that preventive screening of employees only might be sufficient to control outbreaks in nursing homes (on average, one or less secondary infections per index case), provided that turnover times and detection thresholds of the tests are low enough. For the tests considered in this study, we conclude that same-day turnover PCR and RT-LAMP procedures allow for more effective prevention compared to antigen and PCR tests.