PMC:7723248 / 1911-7796 JSONTXT

{"target":"https://pubannotation.org/docs/sourcedb/PMC/sourceid/7723248","sourcedb":"PMC","sourceid":"7723248","source_url":"https://www.ncbi.nlm.nih.gov/pmc/7723248","text":"Introduction\nPathogenic organisms, including bacteria, viruses, fungi, protozoa, and helminths, cause infections that are a leading cause of global morbidity and mortality [1]. In particular, viruses are responsible for diseases such as COVID-19, influenza, hepatitis, Ebola virus disease, and many cases of gastroenteritis. Some of these diseases rely on the spread of viruses in the environment, from infected hosts to susceptible hosts via aerosol, droplet, fomite, and/or fecal-oral routes. Successful transmission requires that the virus survive, or maintain its infectivity, while it is in the environment. Studies on the persistence of viruses in solutions, on material surfaces, and in the air have shown that survival varies by strain, composition of the surrounding media, and environmental factors [2–9].\nAerosol, droplet, and fomite transmission are important routes for the spread of many viral diseases, such as influenza and measles [10]. Viruses can be released from an infected individual or natural sources in aerosols (microscopic droplets small enough to remain airborne for minutes or more) and droplets (larger droplets that quickly deposit onto surfaces). Natural sources of viruses in aerosols and droplets include, for example, seawater [11] and wastewater systems [12]. Aerosols and droplets are complex systems due to their varying size, high surface-to-volume ratio, and spatially heterogeneous composition. Viruses that are immersed in aerosols and droplets experience a dynamic and highly variable microenvironment as aerosols and droplets evaporate and equilibrate with ambient environmental conditions, as illustrated in Fig 1; changes in the microenvironment may affect the viruses’ viability [13].\nFig 1 Factors that affect the survival of viruses in stationary droplets on surfaces. Aerosols and droplets emitted from different sources may have distinct chemical and physical properties. For example, fluids expelled by infected patients when they exhale, talk, cough, or sneeze contain high levels of proteins and are usually viscous [14], while sea spray aerosols contain more salts and organic compounds [15]. Because each chemical component might have a different effect on a virus, its survival in aerosols and droplets that are generated from different sources may vary [16].\nRelatively few studies have investigated the effects of aerosol and droplet composition on the viability of viruses; these studies have focused mainly on the effects of salts and/or proteins. We have shown that high salt concentrations were associated with reduced viability of influenza virus in droplets [17]. In a separate study, we found that influenza virus better retained infectivity in droplets of culture medium that was supplemented with human epithelial bronchial (HBE) cell wash compared to the culture medium alone [18]. HBE cell wash also promoted the survival of the bacteriophage Φ6: it decayed ~2 log10 units in tryptic soy broth (TSB) after 1 h of exposure to 75% RH in aerosols, whereas it did not decay in HBE cell wash under the same conditions [18]. We suspect that proteins in HBE cell wash might have protected the viruses, but the exact reason for the observed difference remains unknown.\nPrior work has focused almost exclusively on virus viability in culture media. However, viruses in the real world are not immersed in culture media; they are present in respiratory fluid, wastewater, freshwater, seawater, and other fluids. Given the complexity of environmental matrices, a more complete understanding of the effect of individual media components on the inactivation of viruses in aerosols and droplets is needed. In addition to salts and proteins, the levels of surfactants and pH vary substantially in environmentally and physiologically relevant fluids [19, 20]. Experiments are needed to disentangle the effects of different chemical components of the fluid on virus viability across the range of concentrations found in environmentally and physiologically relevant sources.\nThe viability of viruses in aerosols and droplets is also affected by environmental factors, such as temperature [21, 22], humidity [16–18, 23–27], and ultraviolet radiation [28–30]. Temperature and ultraviolet radiation primarily affect the viability of viruses by destroying their structural integrity [31]. Other studies have shown that the viability of viruses in both aerosols and droplets depends on relative humidity (RH) [18, 26, 27]. Our previous studies have reported a U-shaped pattern in virus viability as a function of RH in both aerosols and droplets; viruses survived well at RHs lower than 40% or near 100%, but their viability was reduced at intermediate RH [13, 18]. We have proposed that this relationship is mediated by changes in the physicochemical properties of aerosols and droplets as they evaporate to equilibrate with ambient RH [10, 32]. To our best knowledge, there have not been any studies that explore the interaction effects of media composition and relative humidity on virus survival in droplets.\nIn this study, we manipulated the concentrations of several common media components, including salt, protein, and surfactant, as well as pH, over environmentally and physiologically relevant ranges, while quantifying the viability of model viruses in droplets of the media. To gain insight into the interactions between media composition and RH on the viability of viruses in evaporating droplets, we exposed the virus-containing droplets to low, intermediate, and high RH levels for 1 h and evaluated the reduction in virus viability. Results from this study will provide information on the effects of specific media components on the decay of non-enveloped and enveloped viruses in droplets. We hope that addressing this question may enable advances in understanding the mechanisms of virus inactivation in the environment.","divisions":[{"label":"title","span":{"begin":0,"end":12}},{"label":"p","span":{"begin":13,"end":815}},{"label":"p","span":{"begin":816,"end":1731}},{"label":"figure","span":{"begin":1732,"end":1818}},{"label":"label","span":{"begin":1732,"end":1737}},{"label":"caption","span":{"begin":1739,"end":1818}},{"label":"title","span":{"begin":1739,"end":1818}},{"label":"p","span":{"begin":1819,"end":2317}},{"label":"p","span":{"begin":2318,"end":3231}},{"label":"p","span":{"begin":3232,"end":4026}},{"label":"p","span":{"begin":4027,"end":5059}}],"tracks":[]}