Simplified SIR model to predict the progression of COVID-19 Pandemic.

--- In memory of my old friend, Morteza Vejdan MD, MPH, who lost his precious life in the battle against the #CORONA virus, March 25, 2020, Mashad.

Toxicologists model noncommunicable outbreaks and epidemics, including point epidemics, e.g., a botulism outbreak in a wedding (Habibian & Afshari, 2011) or epidemics of a common source, e.g., higher than the regulatory level for a toxic chemical in a customer product (arsenic in drinking water or cosmetic products (Taheri & Afshari, 2014.))

Conceptually, the susceptible population (those who can contract the disease) can be exposed (affected population), and ultimately recover or die (recovered pop).

The modelling of infectious epidemics has an additional la

yer of complexity, because the affected population (here it is called infected) can, in turn, infect other people. As a result, the infection rate will increase exponentially (graph).

Over time, the susceptible population (blue) decreases as it becomes infected . The infected population (red) increases first. Then stabilizes as the susceptible population becomes gradually infected.

The infected population (red) gradually decreases due to recovery (or death) (green) with delay. Graph modified(see comment)