Airborne Transmission of Influenza a Virus in Indoor Environments

dc.contributor.authorYang, Wanen
dc.contributor.committeechairMarr, Linsey C.en
dc.contributor.committeememberLittle, John C.en
dc.contributor.committeememberSubbiah, Elankumaranen
dc.contributor.committeememberPruden, Amyen
dc.contributor.departmentCivil Engineeringen
dc.date.accessioned2017-04-06T15:45:03Zen
dc.date.adate2012-04-26en
dc.date.available2017-04-06T15:45:03Zen
dc.date.issued2012-03-30en
dc.date.rdate2016-10-24en
dc.date.sdate2012-04-01en
dc.description.abstractDespite formidable advances in virology and medicine in recent decades, we know remarkably little about the dynamics of the influenza virus in the environment during transmission between hosts. There is still controversy over the relative importance of various transmission routes, and the seasonality of influenza remains unexplained. This work focuses on developing new knowledge about influenza transmission via the airborne route and the virus' inter-host dynamics in droplets and aerosols. We measured airborne concentrations of influenza A viruses (IAVs) and size distributions of their carrier aerosols in a health center, a daycare center, and airplanes. Results indicate that the majority of viruses are associated with aerosols smaller than 2.5 µm and that concentrations are sufficient to induce infection. We further modeled the fate and transport of IAV-laden droplets expelled from a cough into a room, as a function of relative humidity (RH) and droplet size. The model shows that airborne concentrations of infectious IAV vary with RH through its influence on virus inactivation and droplet size, which shrinks due to evaporation. IAVs associated with large droplets are removed mostly by settling, while those associated with aerosols smaller than 5 µm are removed mainly by ventilation and inactivation. To investigate the relationship between RH and influenza transmission further, we measured the viability of IAV in droplets at varying RHs. Results suggest that there exist three regimes defined by RH: physiological conditions (~100% RH) with high viability, concentrated conditions (~50% to ~99% RH) with lower viability, and dry conditions (<~50% RH) with high viability. A droplet's extent of evaporation, which is determined by RH, affects solute concentrations in the droplet, and these appear to influence viability. This research considerably advances the current understanding of the dynamics of the influenza virus while it is airborne and provides an explanation for influenza's seasonality. Increased influenza activity in winter in temperate regions could be due to greater potential for IAV carrier aerosols to remain airborne and higher viability of IAV at low RH. In tropical regions, transmission could be enhanced due to better survival of IAV at extremely high RH.en
dc.description.degreePh. D.en
dc.identifier.otheretd-04012012-212415en
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-04012012-212415/en
dc.identifier.urihttp://hdl.handle.net/10919/77340en
dc.language.isoen_USen
dc.publisherVirginia Techen
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subjectinfluenza A virusen
dc.subjectairborne transmissionen
dc.subjectrelative humidityen
dc.subjectsize distributionen
dc.subjectbioaerosolen
dc.titleAirborne Transmission of Influenza a Virus in Indoor Environmentsen
dc.typeDissertationen
dc.type.dcmitypeTexten
thesis.degree.disciplineCivil Engineeringen
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen
thesis.degree.leveldoctoralen
thesis.degree.namePh. D.en

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