Simulation of the time course of an epidemics according to the statistical model developed by Reed and Frost

Prof. Andrea Bellelli
UNIVERSITY OF ROMA SAPIENZA
SCHOOL OF PHARMACY AND MEDICINE

Epidemics are a constant treat to mankind, and occur frequently. We have a good understanding of the biochemical mechanisms that govern immunity and susceptibility, but it is sometimes difficult for the student to precisely understand the relationships between biochemical mechanisms, clinical medicine, and epidemiology. This interactive simulation calculates the time course of an epidemics using the statistical - deterministic model developed by Lowell Reed and Wade Hampton Frost. The time scale of the simulation is measured in Serial Generation Times (SGT), defined as the average time required by a person who has been infected to become inefctious and to transmit the disease. Real values for SGT range between a few days and a few weeks; the user may assume SGT=1 week. The student may explore the effect of several variables, most of them biochemical and physiological parameters studied in the basic courses: e.g. immunity or resistence possibly due to genetic variants of virus receptors on the host cell surface. Only one parameter (the nember of contacts, highlighetd in red) is required; for all other variables the program may use defaults (highlighted in bold). It is advisable that the student checks the explanation of the Reed-Frost model at least once, to familiarize with its statistical bases.

 Population size 10k 5k 3k 1k Number of potentially contagious contacts, per individual, during one SGT (notice that this term corresoponds to the maximum theoretical value of the parameter R0 for the simulated epidemics): 10 5 2 1 Percentage of the members of the population who are immune because of vacination or because of a past epidemics by the same agent (default: 0%): 0% 30% 60% 90% Percentage of the members of the population who present lower sensitivity to the disease (default: 0%) 0% 25% 50% 75% Serial Generation Time at which containment measures are introduced (default: never). Containment measures will be kept in place for 10 SGTs. Suggestion: some pairs of R0 and time of quarantine start (TQ) yield clearer pictures than other pairs: try: R0=10, TQ=5; R0=5, TQ=7; or R0=2, TQ=10. never 5 7 10 I want an explanation of the model of epidemics developed by Reed and Frost (default: no) yes no