To a non-expert as most of us comprehending the numbers, the forecasts and the epidemiological parameters presented in the literature may be quite a challenge. I found online a very interesting calculator for COVID that addresses this gap in our understanding.
Figure 1. A calculator to be used to measure one’s risk of exposure to the disease for any given day of the epidemic
The variables for transmission dynamics that can be modified are:
- population inputs: size of population, number of initial infections
- basic reproduction number (measure of contagiousness) : the number of secondary infections each infected individual produces
- transmission times: length of incubation period, duration patient is infectious
The variables for clinical dynamics that can be modified are:
- mortality statistics: fatality rate, time from end of incubation to death
- recovery times : length of hospital stay, recovery time for mild cases
- case statistics: hospitalization rate, time to hospitalization
One may drag horizontally the line for the day of intervention in order to decrease the transmission and then the parameters for susceptible cases, exposed cases, infectious cases, population no longer infectious, fully recovered cases, number of active hospitalizations and fatality rate values will change accordingly.
The infectious disease is mathematically modelled using a compartmental model. The population is assigned to one of the four compartments: susceptible (S), exposed(E), infectious (I) and recovered(R). A mathematical set of equations is used to model the progress of people from one compartment to another. The model runs either on a set of ordinary differential equations (deterministic) or using a stochastic framework (more close to reality).
I attended many online meetings about various models for the clinical data available for COVID cases and I found this model as quite suitable. This epidemiologic calculator uses the SEIR model which assumes that S+E+I+R=N where N is constant as it is assumed that the birth and death rates are equal. I hope this calculator may be of assistance in better administrating the situation with this pandemic.
