key: cord-0744009-y28c1rv0 authors: Pitol, A. K.; Julian, T. R. title: Community Transmission of SARS-CoV-2 by Fomites: Risks and Risk Reduction Strategies date: 2020-11-23 journal: nan DOI: 10.1101/2020.11.20.20220749 sha: a87aab340f4a12cb374ea4adb819a67dff33df8a doc_id: 744009 cord_uid: y28c1rv0 SARS-CoV-2, the virus responsible for the COVID-19 pandemic, is perceived to be primarily transmitted via person-to-person contact, through droplets produced while talking, coughing, and sneezing. Transmission may also occur through other routes, including contaminated surfaces; nevertheless, the role that surfaces have on the spread of the disease remains contested. Here we use the Quantitative Microbial Risk Assessment framework to examine the risks of community transmission of SARS-CoV-2 through contaminated surfaces and to evaluate the effectiveness of hand and surface disinfection as potential interventions. The risks posed by contacting surfaces in communities are low (average of the median risks 1.6x10-4 - 5.6x10-9) for community infection prevalence rates ranging from 0.2-5%. Hand disinfection substantially reduces relative risks of transmission independently of the disease's prevalence and the frequency of contact, even with low (25% of people) or moderate (50% of people) compliance. In contrast, the effectiveness of surface disinfection is highly dependent on the prevalence and the frequency of contacts. The work supports the current perception that contaminated surfaces are not a primary mode of transmission of SARS-CoV-2 and affirms the benefits of making hand disinfectants widely available. is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint The copyright holder for this this version posted November 23, 2020. ; https://doi.org/10.1101/2020.11.20.20220749 doi: medRxiv preprint 3 precautions for particular settings where aerosols are generated and emphasizes the importance of 46 hand hygiene 2 . Nevertheless, the role that airborne and surface-mediated transmission have on the spread of the disease remains contested 1,2,4-7 . 48 49 Indirect transmission via fomites (contaminated surfaces) contributes to the spread of common 50 respiratory pathogens 8-10 and evidence-to-date suggests fomite transmission is possible for SARS-51 CoV-2. People infected with SARS-CoV-2 shed the virus into the environment, as evidenced by 52 extensive SARS-CoV-2 RNA detected on surfaces in cruise ships, hospitals, and public spaces in 53 urban areas such as bus stations and public squares [11] [12] [13] [14] [15] . Infective coronavirus persists in the 54 environment, with experimental evidence of persistence on surfaces ranging from 3 hours to 28 days, 55 depending on environmental factors such as surface material and temperature [16] [17] [18] . Viruses readily 56 transfer from contaminated surfaces to the hand upon contact [19] [20] [21] and from hands to the mucous 57 membranes on the face 21-23 . People touch their faces frequently, with studies reporting average hand-58 to-face contacts ranging from 16 to 37 times an hour [24] [25] [26] is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint The copyright holder for this this version posted November 23, 2020. is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint The copyright holder for this this version posted November 23, 2020. ; https://doi.org/10.1101/2020.11.20.20220749 doi: medRxiv preprint 6 expelled per cough, the distance between the mouth and the hand, and the right circular cone angle of the 120 ejected particles, ( Figure S2 , Table S1 ). Transfer from surface-to-hand and from hand-to-mucous 121 membranes was assumed proportional to the concentration of virus on the surface and the transfer 122 efficiency of virus at both interfaces 38 ( Figure S1 ). The concentration of virus in the contaminated surface 123 was assumed to decay exponentially 52 . Decay rate was obtained from research on SARS-CoV-2 survival 124 on various surfaces 18 . An exponential dose-response model 39 is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint The copyright holder for this this version posted November 23, 2020. is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint The copyright holder for this this version posted November 23, 2020. (5% infection 167 prevalence rate, object contacted once every 1-20 minutes) to 5.6x10 -9 [7.4x10 -12 , 1.6x10 -6 ] in the 168 lowest risk scenario (0.2% prevalence rate, object contacted once every 1-4 hours) (Figure 2) . The 169 overwhelming majority of interactions with fomites modeled were associated with risks < 10 -4 (Table 170 S2). The low risks of community transmission of SARS-CoV-2 via fomites is in accordance with 171 previous studies and opinions of fomite-mediated transmission in hospitals 4-7 . 172 According to the sensitivity analysis, the model parameters most influencing estimated infection risks 173 within a community are transfer efficiency between the surface and the hand, ℎ , and concentration 174 of SARS-CoV-2 in sputum or saliva, (Table S1, Figure S4 ). ℎ was inversely correlated with 175 risk (Spearman's rank correlation, ρ = -0.58) and was directly correlated (ρ = 0.29). Correlation 176 was low with all other modeled parameters (ρ < 0.05). is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint The copyright holder for this this version posted November 23, 2020. is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint The copyright holder for this this version posted November 23, 2020. is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint The copyright holder for this this version posted November 23, 2020. is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint The copyright holder for this this version posted November 23, 2020. ; https://doi.org/10.1101/2020.11.20.20220749 doi: medRxiv preprint with the percent of people who are infected and contact the surface with a hand contaminated by 250 coughing. In reality, an unknown fraction of infected people would likely either: 1) stay at home (i.e., 251 quarantine and/or isolation), or 2) not cough directly on their hand. In this regard, the modeled 252 infection risks are likely higher (more conservative) than would be expected at the stated community 253 infection prevalence rates. is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint The copyright holder for this this version posted November 23, 2020. is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint The copyright holder for this this version posted November 23, 2020. ; https://doi.org/10.1101/2020.11.20.20220749 doi: medRxiv preprint Scientic Brief: SARS-CoV-2 and Potential Airborne 278 World Health Organization. Transmission of SARS-CoV-2: implications for infection 280 prevention precautions. Scientific brief Quantifying SARS-CoV-2 transmission suggests epidemic control with 282 digital contact tracing. 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