{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,29]],"date-time":"2026-06-29T19:42:22Z","timestamp":1782762142591,"version":"3.54.5"},"reference-count":46,"publisher":"AIP Publishing","issue":"1","content-domain":{"domain":["pubs.aip.org"],"crossmark-restriction":true},"short-container-title":[],"published-print":{"date-parts":[[2021,1,1]]},"abstract":"<jats:p>Airborne respiratory diseases such as COVID-19 pose significant challenges to public transportation. Several recent outbreaks of SARS-CoV-2 indicate the high risk of transmission among passengers on public buses if special precautions are not taken. This study presents a combined experimental and numerical analysis to identify transmission mechanisms on an urban bus and assess strategies to reduce risk. The effects of the ventilation and air-conditioning systems, opening windows and doors, and wearing masks are analyzed. Specific attention is paid to the transport of submicron- and micron-sized particles relevant to typical respiratory droplets. High-resolution instrumentation was used to measure size distribution and aerosol response time on a campus bus of the University of Michigan under these different conditions. Computational fluid dynamics was employed to measure the airflow within the bus and evaluate risk. A risk metric was adopted based on the number of particles exposed to susceptible passengers. The flow that carries these aerosols is predominantly controlled by the ventilation system, which acts to uniformly distribute the aerosol concentration throughout the bus while simultaneously diluting it with fresh air. The opening of doors and windows was found to reduce the concentration by approximately one half, albeit its benefit does not uniformly impact all passengers on the bus due to the recirculation of airflow caused by entrainment through windows. Finally, it was found that well fitted surgical masks, when worn by both infected and susceptible passengers, can nearly eliminate the transmission of the disease.<\/jats:p>","DOI":"10.1063\/5.0037452","type":"journal-article","created":{"date-parts":[[2021,1,12]],"date-time":"2021-01-12T22:49:53Z","timestamp":1610491793000},"update-policy":"https:\/\/doi.org\/10.1063\/aip-crossmark-policy-page","source":"Crossref","is-referenced-by-count":138,"title":["Disease transmission through expiratory aerosols on an urban\n          bus"],"prefix":"10.1063","volume":"33","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-9398-072X","authenticated-orcid":false,"given":"Zhihang","family":"Zhang","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2030-5891","authenticated-orcid":false,"given":"Taehoon","family":"Han","sequence":"additional","affiliation":[{"name":"Department of Mechanical Engineering, University of Michigan 2 , 2045 AL (W.E. Lay Auto Lab), 1231 Beal, Ann Arbor, Michigan 48109-2121,","place":["USA"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7541-3553","authenticated-orcid":false,"given":"Kwang Hee","family":"Yoo","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1684-4967","authenticated-orcid":false,"given":"Jesse","family":"Capecelatro","sequence":"additional","affiliation":[{"name":"Department of Mechanical Engineering, University of Michigan 3 , 2011 AL (W.E. Lay Auto Lab), 1231 Beal, Ann Arbor, Michigan 48109-2121,","place":["USA"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0965-9288","authenticated-orcid":false,"given":"Andr\u00e9 L.","family":"Boehman","sequence":"additional","affiliation":[{"name":"Department of Mechanical Engineering, University of Michigan 2 , 2045 AL (W.E. Lay Auto Lab), 1231 Beal, Ann Arbor, Michigan 48109-2121,","place":["USA"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7286-7402","authenticated-orcid":false,"given":"Kevin","family":"Maki","sequence":"additional","affiliation":[{"name":"Department of Naval Architecture and Marine Engineering, University of Michigan 4 , 210 NAME Bldg, 2600 Draper Drive, Ann Arbor, Michigan 48109-2145,","place":["USA"]}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"317","published-online":{"date-parts":[[2021,1,12]]},"reference":[{"key":"2025052812015269400_c1","doi-asserted-by":"publisher","first-page":"14857","DOI":"10.1073\/pnas.2009637117","article-title":"Identifying airborne\n            transmission as the dominant route for the spread of COVID-19","volume":"117","year":"2020","journal-title":"Proc. Natl. Acad. Sci. U. S. A."},{"key":"2025052812015269400_c2","author":"W. H. Organization","year":"2020"},{"key":"2025052812015269400_c3","doi-asserted-by":"publisher","first-page":"F1-1","DOI":"10.1017\/jfm.2020.720","article-title":"Effects of ventilation on the\n            indoor spread of COVID-19","volume":"903","year":"2020","journal-title":"J. Fluid Mech."},{"key":"2025052812015269400_c4"},{"key":"2025052812015269400_c5","doi-asserted-by":"publisher","first-page":"1665","DOI":"10.1001\/jamainternmed.2020.5225","article-title":"Community outbreak investigation of\n            SARS-CoV-2 transmission among bus riders in Eastern China","volume":"180","year":"2020","journal-title":"JAMA\n            Intern. Med."},{"key":"2025052812015269400_c6","doi-asserted-by":"publisher","first-page":"537","DOI":"10.1017\/jfm.2014.88","article-title":"Violent expiratory events: On\n            coughing and sneezing","volume":"745","year":"2014","journal-title":"J. Fluid Mech."},{"key":"2025052812015269400_c7","doi-asserted-by":"crossref","unstructured":"M.\n            Abkarian\n          , S.Mendez, N.Xue, F.Yang, and H. A.Stone, \u201cPuff trains in speaking produce\n            long-range turbulent jet-like transport potentially relevant to asymptomatic spreading\n            of viruses,\u201d arXiv:2006.10671\n            (2020).","DOI":"10.1073\/pnas.2012156117"},{"key":"2025052812015269400_c8","doi-asserted-by":"publisher","DOI":"10.1111\/ina.12751","article-title":"Transmission of SARS-CoV-2 by\n            inhalation of respiratory aerosol in the skagit valley chorale superspreading\n            event","year":"2020","journal-title":"Indoor Air."},{"key":"2025052812015269400_c9","doi-asserted-by":"publisher","first-page":"104866","DOI":"10.1016\/j.ssci.2020.104866","article-title":"Modelling aerosol transport and\n            virus exposure with numerical simulations in relation to SARS-CoV-2 transmission by\n            inhalation indoors","volume":"130","year":"2020","journal-title":"Saf. Sci."},{"key":"2025052812015269400_c10","doi-asserted-by":"publisher","first-page":"67","DOI":"10.1016\/j.buildenv.2011.05.003","article-title":"An advanced numerical model\n            for the assessment of airborne transmission of influenza in bus\n            microenvironments","volume":"47","year":"2017","journal-title":"Build. Environ."},{"key":"2025052812015269400_c11","doi-asserted-by":"publisher","first-page":"434","DOI":"10.1016\/j.atmosenv.2017.08.053","article-title":"Effects of the window openings on\n            the micro-environmental condition in a school bus","volume":"167","year":"2017","journal-title":"Atmos.\n            Environ."},{"key":"2025052812015269400_c12","doi-asserted-by":"publisher","first-page":"122609","DOI":"10.1016\/j.jhazmat.2020.122609","article-title":"Transmission of pathogen-laden\n            expiratory droplets in a coach bus","volume":"397","year":"2020","journal-title":"J. Hazard. Mater."},{"key":"2025052812015269400_c13","doi-asserted-by":"publisher","first-page":"1396","DOI":"10.1016\/j.apr.2020.05.021","article-title":"The influence of school bus\n            ventilation scenarios over in-cabin PM number concentration and air exchange\n            rates","volume":"11","year":"2020","journal-title":"Atmos. Pollut. Res."},{"key":"2025052812015269400_c14","doi-asserted-by":"publisher","first-page":"500","DOI":"10.1111\/ina.12465","article-title":"Airborne spread of expiratory\n            droplet nuclei between the occupants of indoor environments: A review","volume":"28","year":"2018","journal-title":"Indoor Air"},{"key":"2025052812015269400_c15","doi-asserted-by":"publisher","first-page":"514","DOI":"10.1177\/1420326x16631596","article-title":"Ventilation of general hospital\n            wards for mitigating infection risks of three kinds of viruses including Middle East\n            respiratory syndrome coronavirus","volume":"26","year":"2017","journal-title":"Indoor Built\n            Environ."},{"key":"2025052812015269400_c16","doi-asserted-by":"publisher","first-page":"105585","DOI":"10.1016\/j.jaerosci.2020.105585","article-title":"Influence of wind and relative\n            humidity on the social distancing effectiveness to prevent COVID-19 airborne\n            transmission: A numerical study","volume":"147","year":"2020","journal-title":"J. Aerosol Sci."},{"key":"2025052812015269400_c17","article-title":"Bus network redesign and\n            timetable optimization"},{"key":"2025052812015269400_c18","doi-asserted-by":"publisher","first-page":"611","DOI":"10.1093\/oxfordjournals.aje.a118097","article-title":"On air-borne infection: Study\n            II. Droplets and droplet nuclei","volume":"20","year":"1934","journal-title":"Am. J. Epidemiol."},{"key":"2025052812015269400_c19","doi-asserted-by":"publisher","first-page":"063303","DOI":"10.1063\/5.0015044","article-title":"On respiratory droplets and\n            face masks","volume":"32","year":"2020","journal-title":"Phys. Fluids"},{"key":"2025052812015269400_c20","doi-asserted-by":"publisher","first-page":"555","DOI":"10.1038\/s41423-020-0407-x","article-title":"Covid-19: A new challenge for\n            human beings","volume":"17","year":"2020","journal-title":"Cell. Mol. Immunol."},{"key":"2025052812015269400_c21","doi-asserted-by":"publisher","first-page":"507","DOI":"10.1016\/s0140-6736(20)30211-7","article-title":"Epidemiological and clinical\n            characteristics of 99 cases of 2019 novel coronavirus pneumonia in Wuhan, China: A\n            descriptive study","volume":"395","year":"2020","journal-title":"Lancet"},{"key":"2025052812015269400_c22","volume-title":"Computational Methods for Fluid\n            Dynamics","year":"2002"},{"key":"2025052812015269400_c23","volume-title":"Fluid Mechanics","year":"2008","edition":"4"},{"key":"2025052812015269400_c24","first-page":"96","article-title":"The numerical computation of\n            turbulent flows","volume-title":"Numerical Prediction of Flow, Heat\n            Transfer, Turbulence and Combustion","year":"1983"},{"key":"2025052812015269400_c25","doi-asserted-by":"publisher","first-page":"105","DOI":"10.1089\/jam.1997.10.105","article-title":"The size distribution of\n            droplets in the exhaled breath of healthy human subjects","volume":"10","year":"1997","journal-title":"J.\n            Aerosol Med."},{"key":"2025052812015269400_c26","doi-asserted-by":"publisher","first-page":"e2691","DOI":"10.1371\/journal.pone.0002691","article-title":"Influenza virus in human\n            exhaled breath: An observational study","volume":"3","year":"2008","journal-title":"PLoS One"},{"key":"2025052812015269400_c27","doi-asserted-by":"publisher","first-page":"1437","DOI":"10.1002\/cphy.c100085","article-title":"Particle transport and\n            deposition: Basic physics of particle kinetics","volume":"3","year":"2011","journal-title":"Compr.\n            Physiol."},{"key":"2025052812015269400_c28","doi-asserted-by":"publisher","first-page":"121901","DOI":"10.1063\/1.5127787","article-title":"Aerosol transport in a\n            breathing alveolus","volume":"31","year":"2019","journal-title":"Phys. Fluids"},{"key":"2025052812015269400_c29","doi-asserted-by":"publisher","first-page":"1375","DOI":"10.1152\/japplphysiol.01117.2014","article-title":"Revisiting pulmonary acinar\n            particle transport: Convection, sedimentation, diffusion, and their\n            interplay","volume":"118","year":"2015","journal-title":"J. Appl. Physiol."},{"key":"2025052812015269400_c30","doi-asserted-by":"publisher","first-page":"093312","DOI":"10.1063\/5.0024272","article-title":"Weather impact on airborne\n            coronavirus survival","volume":"32","year":"2020","journal-title":"Phys. Fluids"},{"key":"2025052812015269400_c31","doi-asserted-by":"publisher","first-page":"201","DOI":"10.1016\/s0360-1323(00)00095-0","article-title":"Design and evaluation of a\n            minienvironment for semiconductor manufacture processes","volume":"37","year":"2002","journal-title":"Build.\n            Environ."},{"key":"2025052812015269400_c32","doi-asserted-by":"publisher","first-page":"75","DOI":"10.1016\/j.buildenv.2010.07.003","article-title":"Distributions of respiratory\n            contaminants from a patient with different postures and exhaling modes in a single-bed\n            inpatient room","volume":"46","year":"2011","journal-title":"Build. Environ."},{"key":"2025052812015269400_c33","doi-asserted-by":"publisher","first-page":"1329","DOI":"10.1016\/j.buildenv.2004.11.009","article-title":"Study on inhalation region by\n            means of CFD analysis and experiment","volume":"40","year":"2005","journal-title":"Build. Environ."},{"key":"2025052812015269400_c34","doi-asserted-by":"publisher","first-page":"144","DOI":"10.1111\/j.1600-0668.2004.00283.x","article-title":"Analysis and design of\n            micro-climate around the human body with respiration by CFD","volume":"14","year":"2004","journal-title":"Indoor Air"},{"key":"2025052812015269400_c35","doi-asserted-by":"publisher","first-page":"053310","DOI":"10.1063\/5.0011960","article-title":"On coughing and airborne\n            droplet transmission to humans","volume":"32","year":"2020","journal-title":"Phys. Fluids"},{"key":"2025052812015269400_c36","doi-asserted-by":"publisher","first-page":"311","DOI":"10.1038\/d41586-020-01056-7","article-title":"How does COVID-19 kill?\n            Uncertainty is hampering doctors\u2019 ability to choose treatments","volume":"580","year":"2020","journal-title":"Nature"},{"key":"2025052812015269400_c37","doi-asserted-by":"crossref","unstructured":"J.\n              M.\n            Kolinski\n           and T. M.Schneider, \u201cSuperspreading events\n            suggest aerosol transmission of SARS-CoV-2 by accumulation in enclosed\n            spaces,\u201d arXiv:2007.14807\n            (2020).","DOI":"10.1103\/PhysRevE.103.033109"},{"key":"2025052812015269400_c38","doi-asserted-by":"publisher","first-page":"1","DOI":"10.1016\/j.physrep.2019.01.008","article-title":"Evaporation of a droplet: From\n            physics to applications","volume":"804","year":"2019","journal-title":"Phys. Rep."},{"key":"2025052812015269400_c39","doi-asserted-by":"publisher","first-page":"105794","DOI":"10.1016\/j.envint.2020.105794","article-title":"Estimation of airborne viral\n            emission: Quanta emission rate of SARS-CoV-2 for infection risk\n            assessment","volume":"141","year":"2020","journal-title":"Environ. Int."},{"key":"2025052812015269400_c40","doi-asserted-by":"publisher","first-page":"235","DOI":"10.1016\/j.jhin.2015.08.027","article-title":"Transmission of SARS and MERS\n            coronaviruses and influenza virus in healthcare settings: The possible role of dry\n            surface contamination","volume":"92","year":"2016","journal-title":"J. Hosp. Infect."},{"key":"2025052812015269400_c41","doi-asserted-by":"publisher","first-page":"1564","DOI":"10.1056\/nejmc2004973","article-title":"Aerosol and surface stability of\n            SARS-CoV-2 as compared with SARS-CoV-1","volume":"382","year":"2020","journal-title":"N. Engl. J.\n            Med."},{"key":"2025052812015269400_c42","doi-asserted-by":"publisher","first-page":"1175","DOI":"10.1080\/10789669.2009.10390885","article-title":"Experimental study on\n            displacement and mixing ventilation systems for a patient ward","volume":"15","year":"2009","journal-title":"HVACR Res."},{"key":"2025052812015269400_c43","doi-asserted-by":"publisher","first-page":"122","DOI":"10.1016\/j.jaerosci.2008.10.003","article-title":"Characterization of expiration air\n            jets and droplet size distributions immediately at the mouth opening","volume":"40","year":"2009","journal-title":"J. Aerosol Sci."},{"key":"2025052812015269400_c44","doi-asserted-by":"publisher","first-page":"471","DOI":"10.1017\/s0022172400019288","article-title":"The size and the duration of\n            air-carriage of respiratory droplets and droplet-nuclei","volume":"44","year":"1946","journal-title":"Epidemiol. Infect."},{"key":"2025052812015269400_c45","doi-asserted-by":"publisher","first-page":"435","DOI":"10.1164\/arrd.1967.95.3.435","article-title":"Droplet expulsion from the\n            respiratory tract","volume":"95","year":"1967","journal-title":"Am. Rev. Respir. Dis."},{"key":"2025052812015269400_c46","doi-asserted-by":"publisher","first-page":"162","DOI":"10.1016\/j.pecs.2005.11.001","article-title":"Advanced models of fuel droplet\n            heating and evaporation","volume":"32","year":"2006","journal-title":"Prog. Energy Combust. Sci."}],"container-title":["Physics of Fluids"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/pubs.aip.org\/aip\/pof\/article-pdf\/doi\/10.1063\/5.0037452\/20532354\/015116_1_5.0037452.pdf","content-type":"application\/pdf","content-version":"vor","intended-application":"syndication"},{"URL":"https:\/\/pubs.aip.org\/aip\/pof\/article-pdf\/doi\/10.1063\/5.0037452\/20532354\/015116_1_5.0037452.pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,5,28]],"date-time":"2025-05-28T16:01:59Z","timestamp":1748448119000},"score":1,"resource":{"primary":{"URL":"https:\/\/pubs.aip.org\/pof\/article\/33\/1\/015116\/1061137\/Disease-transmission-through-expiratory-aerosols"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2021,1,1]]},"references-count":46,"journal-issue":{"issue":"1","published-print":{"date-parts":[[2021,1,1]]}},"URL":"https:\/\/doi.org\/10.1063\/5.0037452","relation":{},"ISSN":["1070-6631","1089-7666"],"issn-type":[{"value":"1070-6631","type":"print"},{"value":"1089-7666","type":"electronic"}],"subject":[],"published-other":{"date-parts":[[2021,1,1]]},"published":{"date-parts":[[2021,1,1]]},"article-number":"015116"}}