Community transmission of SARS-CoV‑2 by surfaces: risks and risk reduction strategies

SARS-CoV-2, the virus responsible for the COVID-19 pandemic, isperceived to be primarily transmitted via person-to-person contact throughdroplets produced while talking, coughing, and sneezing. Transmission may alsooccur through other routes, including contaminated surfaces; nevertheless, the rolethat surfaces have on the spread of the disease remains contested. Here, we use theQuantitative Microbial Risk Assessment framework to examine the risks ofcommunity transmission of SARS-CoV-2 through surfaces and to evaluate theeffectiveness of hand and surface disinfection as potential interventions. Usingconservative assumptions on input parameters of the model (e.g., dose−responserelationship, ratio of genome copies to infective virus), the average of the medianrisks for single hand-to-surface contact followed by hand-to-face contact range from 1.6×10−4 to 5.6×10−9 for modeled prevalencerates of 0.2%−5%. For observed prevalence rates (0.2%, 1%), this corresponds to a low risk of infection (<10−6). Hand disinfectionsubstantially reduces risks of transmission independently of the disease's prevalence and contact frequency. In contrast, theeffectiveness of surface disinfection is highly dependent on the prevalence and the frequency of contacts. The work supports thecurrent perception that contaminated surfaces are not a primary mode of transmission of SARS-CoV-2 and affirms the benefits ofmaking hand disinfectants widely available.