The relative viability of MS2 in droplets with different surfactant concentrations is shown in Fig 5A and 5C. MS2 generally survived better when SDS was present in droplets, and relative viability increased with SDS concentration at 20% and 80% RH. MS2 incurred no decay in droplets containing 10 μg/mL SDS, whereas it at least lost 25% viability in droplets containing no SDS. The relationship between viability and SDS concentration differed at 50% RH, at which MS2 survived best in droplets with 1 μg/mL SDS, but decayed most in droplets containing 10 μg/mL SDS. As shown in Fig 5B and 5D, SDS did not significantly affect the viability of Φ6 in droplets at RHs of 20%. However, 10 μg/mL SDS induced a significantly higher inactivation of Φ6 at RHs of 50% and 80%; no viable Φ6 was recovered from droplets containing 10 μg/mL SDS at high RH after 1 h.