This model allows students to examine the effects of mutation and masking on the max daily cases and epidemic duration in a population. Both human beings and viruses are represented in the model.
Grades: 9-12; Intro Biology
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HOW IT WORKS
1. Susceptible-infectious-recovered (SIR) model is used to build the present model.
2. The model starts with a population of susceptible people (green) and one infectious person (orange). The infectious person carries the virus strain with the defined initial transmission rate.
3. In each tick, each infectious person produces a new virus. The virus transmission rate either stays the same or mutates to become more or less transmissible at the defined mutation rate.
4. The new virus may float 0.5 steps in a random direction and infect one of susceptible people within a radius of 1.5 at its transmission rate. The virus loses its ability to infect people if no susceptible people are within the infection radius.
5. Infectious people remain contagious for six days. They either recover (become blue) or die at a mortality rate of 10%. No new people join this model to maintain the population density.
6. Users may set up the percentage of masking in the population. The masked infectious people release 50% less viable viruses than unmasked infectious people. The transmission rate of a virus decreases by 50% when infecting a masked susceptible person (i.e., 70% become 35%, 50% become 25%, and so on).
7. Users may set up the percentage of vaccinated people in the population. The present model assumes the vaccinated people will not be infected. However, the vaccinated people may get breakthrough infection at a low chance when viruses mutate.
HOW TO USE IT
First, choose the factors, such as population size, transmission rate, etc.
Click on Set up/Reset, then Run/Pause. The model is set to stop when there are no infectious people.
Observe the infection changes in the population in the plot and monitor.
Use Run one day to run the model in a controlled way and collect day-by-day data.
The people in the model are color-coded in two ways: SIR coloring and transmission rate coloring. The mode of SIR coloring displays the population based on people's health status (i.e., susceptible, infectious, or recovered); the mode of transmission rate coloring displays the population based on the virus transmissibility when the people get infected (i.e., cyan and brown indicate the people who are infected by the less transmissible strains while red and purple indicate the people who are infected by the highly transmissible strains). Use the button Switch color-coding mode or the switch Color-coding-modes to switch between the two modes.
THINGS TO TRY
Collect the data of the max daily cases and epidemic duration to examine the effects of mutation rates and % of masking.
CREDITS AND REFERENCES
CREDITS AND REFERENCES
Dr. Lin Xiang (lin.xiang@uky.edu) created this module at the University of Kentucky in 2022. If you mention this model in a publication, we ask that you include the citations below.
Xiang, L. (2022). Infectious Disease Outbreak-Mutation and Masking. Department of STEM Education, University of Kentucky, Lexington, KY.
This work is licensed under the Creative Commons Attribution-NonCommercial-ShareAlike 4.0 License. To view a copy of this license, visit https://creativecommons.org/licenses/by-nc-sa/4.0/.
Science Brief: Community Use of Masks to Control the Spread of SARS-CoV-2 https://www.cdc.gov/coronavirus/2019-ncov/science/science-briefs/masking-science-sars-cov2.html
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