Before revision:  While the initially near unity infection probability due to droplets (airborne/ballistic) rapidly decays within the first 25s, the small yet persistent infection probability of airborne desiccated nuclei decays appreciably only by  1000s  . Combined with molecular collision theory adapted to calculate frequency of contact between the susceptible population and the droplet/nuclei cloud, infection probabilities are used to define infection rate constants , ab-initio, leading to a SEIR model .
After revision:  While the initially near unity infection probability due to droplets (airborne/ballistic) rapidly decays within the first 25s, the small yet persistent infection probability of airborne desiccated nuclei decays appreciably only by 1000s . Combined with molecular collision theory adapted to calculate frequency of contact between the susceptible population and the droplet/nuclei cloud, infection rate constants are derived ab-initio, leading to a SEIR model .