Similar to its effect on MS2, BSA protected Φ6 from inactivation in droplets at intermediate and high RHs (Fig 4B and 4D). At 20% RH, the relative viability of Φ6 was similar in droplets with and without BSA. However, at 50% RH, the relative viability of Φ6 was significantly higher in droplets containing 1000 μg/mL BSA than in droplets with 0 or 100 μg/mL BSA. At 80% RH, the presence of BSA, regardless of its concentration, reduced the decay of Φ6 in droplets, suggesting its protective effect on viruses in droplets again.