Transmission Dynamics of COVID-19 and Impact on Public Health Policy

B Shayak; Mohit Manoj Sharma; Richard H Rand; Awadhesh Kumar Singh; Anoop Misra

We shall now begin the derivation of the Coronavirus dynamic model. The derivation is involved, and the final model itself is (7). The flow diagram of people from one category to the other looks like the following, where R denotes a flow rate (i.e. d/dt of a population). In this schematic, R1 is the rate at which healthy, at-large people fall sick, R2 is the rate at which people arrive for quarantine and testing, R3 is the rate at which positive results are detected and R4 is the rate at which negative results are detected. We take for granted that every person who is tested for the virus is in quarantine. We shall now elaborate on the functional forms of these rates. is the author/funder, who has granted medRxiv a license to display the (which was not peer-reviewed) The copyright holder for this preprint . https://doi.org/10.1101/2020.03. 29.20047035 doi: medRxiv preprint Tradition has it to make R1 proportional to the number of healthy (and susceptible -even when we don't mention this explicitly) people and the number of sick people, i.e. to make R1 have the form kxy where k is some constant. We follow the tradition with a variation. First, recall that by our definition, sick people stay sick for all time. However, they do not transmit the disease for all time. Consider an asymptomatic carrier who remains exposed to society throughout. We assume that the number of asymptomatics is proportional to the total number of sick people exposed to society, i.e. we let the number of asymptomatics be μ1y where μ1 is a number between 0 and 1. After falling sick, an asymptomatic carrier can transmit the disease for 7-10 days, which is called the infection period [46] . Thus, new healthy people can be only be infected by those asymptomatic sick people who have fallen sick within the last 7-10 days, and not those who have fallen sick earlier. The number of such people is the number of asymptomatic sick people today minus the number of those 7-10 days earlier i.e. it is ( )