UC San Diego

Case investigation and contact tracing (CICT) is a strategy for preventing transmission of infectious diseases, deployed during the COVID-19 pandemic, to identify individuals before becoming symptomatic and/or infectious so they could test and quarantine in order to break chains of transmission. Since May 11, 2020, the UC San Diego Return to Learn program conducted CICT for UCSD students, faculty, and staff. Data collected through contact tracing efforts provides an estimate for adherence to social distancing efforts. Our study aimed to identify the number of close contacts per case as well as factors associated with changes in the number of close contacts. Using available data, cases investigated between July 2020 and April 2021, we examined case characteristics and determined the number of close contacts reported by cases over time. Trends in the number of contacts per case over time were examined using linear regression. Of the 968 cases investigated during this period, 33.9% were White/Middle Eastern, 51.1% were female, and 63.2% were 18-29 years old. Cases were stratified based on university affiliation, in which 56.4% were students (including student employees) and 43.6% were employees of UC San Diego. Findings indicated that the number of close contacts per case had a statistically significant association with age group and student status. Analyses showed an increase in the mean number of close contacts per case over time. Furthermore, we observed that the number of contacts per case increased after stay-at-home orders ended in San Diego county (p<0.001), but did not decrease after business closures and mask mandates were implemented (p=0.76). These findings suggest that changes in time and mitigation protocols (i.e., quarantine) can impact social distancing adherence by proxy of close contacts, which provide insights for future outbreak mitigation efforts and policy planning.