What is R_0?

A key quantity in epidemiology is R_0: the basic reproduction number  (which you may have heard about in the news). R_0 , is the number of people that a given person is likely to infect. A good diagram of this is shown below for Ebola with R_0 = 2 and the 2002 SARS outbreak with R_0 = 4. Given that the number of people to whom an infected person is likely to spread the disease will depend on mitigation measures, R_0 will change over the course of the outbreak. A disease with R_0 > 1 will continue to spread (the number of people continues to grow), meanwhile R_0 < 1 results in the number of cases declining. Given that R_0 is just a number of people, it is a unit-less number.

Our goal

Measure R_0 for different stages of the COVID-19 pandemic in the United States during 2020.

 

R Naught is the average number of people infected from one other person, for example, ebola has an r-naught of two, so on average for every one person who has ebola they will pass it on the two other people.
R_0 is the average number of people infected from one other person, for example, ebola has an R_0 = 2, so on average for every one person who has ebola they will pass it on the two other people.
KieraCampbell, CC BY-SA 4.0, via Wikimedia Commons.

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Physics 132 Lab Manual by Brokk Toggerson and Aidan Philbin is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License, except where otherwise noted.

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