PMC:3463543 / 17223-19800 JSONTXT

{"project":"2_test","denotations":[{"id":"23056454-17850213-92972557","span":{"begin":1856,"end":1858},"obj":"17850213"},{"id":"23056454-4324730-92972558","span":{"begin":1920,"end":1922},"obj":"4324730"},{"id":"23056454-11777428-92972559","span":{"begin":2335,"end":2337},"obj":"11777428"},{"id":"23056454-11777428-92972560","span":{"begin":2363,"end":2365},"obj":"11777428"}],"text":"Hypothesis to Explain the Relationship between RH and Viability in Laboratory Studies\nWe postulate that there exist three regimes governing the viability of IAV in droplets, defined by ambient RH and shown in Figure 4: (1) physiological conditions (∼99 to 100% RH), where solute concentrations remain at levels harmless to IAV and viability is maintained, (2) concentrated conditions (∼50 to ∼99% RH), where evaporation leads to elevated salt concentrations that may be harmful to the virus, and (3) dry conditions (\u003c50% RH), where solutes crystallize, all water is lost, and IAV viability is maintained.\nFigure 4 Hypothesized relationship between RH and IAV viability in (A) droplets containing salts only and (B) droplets containing salts plus proteins. In a saline droplet, the elevated salt concentrations that result from evaporation are likely to be toxic to the virus, but such deleterious effects would be eliminated when the solution crystallizes. Therefore, the minimum viability would be expected at an RH just above the ERH of the salts contained in the droplet, when water is still present and solute concentrations are maximal. The relationship between RH and IAV viability in a saline droplet would thus be similar to that shown in Figure 4A. However, the presence of proteins in the droplet may alter this relationship. It is possible that the interaction between proteins, salts, and the virus mitigates the adverse effects of salts under concentrated conditions. Therefore, the virus would maintain high viability under physiological and dry conditions and moderate viability under concentrated conditions in a droplet composed of both salts and proteins (Figure 4B). In fact, viability may increase with decreasing RH, as we found in DMEM+FCS and mucus, possibly due to protection provided by proteins at elevated concentrations [28], [29].\nA study on Langat virus supports our hypothesis. Benbough [30] reported similar V-shaped curves of viability versus RH for Langat virus in aerosols composed of salt solutions. Of four RHs tested (i.e., ∼25%, 50%, 70%, and 95%), the minimum viabilities were ∼1% in NaCl and ∼10% in KCl, both at ∼50% RH, and zero in LiCl at RH\u003c50%. Thus, the minimum viability of Langat virus in aerosols composed of an NaCl solution occurred at an RH close to the ERH of NaCl (i.e., 43±3%) [27]. KCl has an ERH of 59% [27], and this RH was not tested, so it is unknown whether the virus’ viability would have been lower at this RH. The ERH of LiCl, if it exists, is outside the range of RHs tested; its deliquescence RH is ∼11% [24]."}