The viability of viruses in droplets was studied in an environmental chamber (5518; Electro-Tech Systems) at room temperature (22 ± 1°C). For each virus suspension, droplets were exposed at low, intermediate, and high RH levels of 20%, 50%, and 80%, respectively. The targeted RH inside the environmental chamber was achieved by vaporizing ultrapure water with a humidifier or passing air through a desiccator. Fifteen minutes after the RH reached equilibrium, ten separate 1-μL droplets of virus suspension were spotted on a 6-well, polystyrene cell culture plate (SIAL0516; Sigma) with a 0.1-10-μL pipette. Droplets were incubated for 1 h, after which viruses were collected in 500 μL of LB medium by pipetting up and down several times. Samples were stored at -80°C immediately after collection until they were quantified by plaque assay. Control samples containing 10 μL of virus suspension in a sealed 1.5-mL microcentrifuge tube were incubated inside the environmental chamber during each experiment and collected in 500 μL of culture medium after 1 h.