  The transmission of viruses/ bacteria cause infection predominantly via
aerosols. The transmission mechanism of respiratory diseases is complex,
including direct or indirect contact, large droplet, and airborne routes apart
from close contact transmission. With this pretext, we have investigated two
modes of droplet evaporation to understand its significance in airborne disease
transmission; a droplet in a contact-free environment, which evaporates and
forms droplet nuclei, and a droplet on a hydrophilic substrate (fomite). The
study examines mass transport, the deposition pattern of bacteria in the
precipitates, and their survival and virulence. The osmotic pressure increases
with the salt concentration, inactivating the bacteria embedded in the
precipitates with accelerated evaporation. Further, the bacteria's degree of
survival and enhanced pathogenicity are compared for both evaporation modes.
The striking differences in pathogenicity are attributed to the evaporation
rate, oxygen availability, and reactive oxygen species (ROS) generation.
