Evaporating 1-μl droplets exposed to 60% RH for 1 h.

<p>1-μl droplets containing inactivated influenza A virus (equivalent to 1E7 PFU/ml) exposed to 60% RH for an hour. The initial composition was the following: NaCl 8 g/l in milli-Q water (1st column); albumin 8.8 g/l + NaCl 8 g/l in milli-Q water (2nd column); transferrin 8.8 g/l + NaCl 8 g/l in milli-Q water (3rd column);&nbsp;casein 8.8 g/l + NaCl 8 g/l in milli-Q water (4th column);&nbsp;synthetic lung fluid (5th column).</p>