where is the safest place to have a large droplet evaporate?
It is the essence of disease transmission that infectious viruses are carried by droplets. After being exhaled from the host, the droplets will conduct heat, participate in mass transfer, and undergo an evaporation exchange with the environment. The viral survival condition, such as saltwater, nutrient, salt, pH, temperature, and humidity balance, are significantly influenced by various environmental factors. The viruses can only enter the host “luckily” and cause infection when the concentration is sufficient and the virus is still alive, which is unfortunate for the susceptible population. Thus, the different risk of when and how to contact the infectious viruses is the most important question that should be answered, to provide a reference for early isolation and the mask dispute.
Based on the different particle sizes, we conducted an in-depth review on the physical processes and transmission risks of viral infections caused by infectious droplets at different time points. We found that the viral load of large droplets was several orders of magnitude larger than that of small droplets. The disease transmission ability of large droplets at the initial moment is significantly higher than that of small droplets. Furthermore, during the transmission process, the original large droplets evaporation takes longer, and the survival condition balance of active viruses is better maintained, and becomes a high-risk small droplet nuclei carrying a massive number of active viruses after evaporation. Compared with the original small droplets, whose internal viruses are quickly evaporated and inactivated, the risk difference of disease transmission between the two is even greater, which also confirmed the dominant position of large droplets in disease transmission.
