The R Value and disease spread – learn more about what this means with COVID-19

There is a lot of talk in the news about keeping the R-value below now, but what does this mean?

“R nought,” is a mathematical term that is used to indicate how contagious an infectious disease is. It’s also referred to as the reproduction number as it reflects the rate of transmission to new people as it reproduces itself.  It is used to make policy decisions as to what controls to put in place.

R, tells you the average number of people who will contract a contagious disease from one person who was previously free of infection and haven’t been vaccinated.

For example, if a virus has an R of 5, a person who has the disease will transmit it to an average of 5 other people and therefore the virus spreads easily and quickly.

If a disease has an R of 1, a person with the disease will on average pass it to one other person, therefore the disease transmission stays at the same rate.

The goal is to have an R-value of less than one for example of 0.5 meaning that to an infected person would infect on average 0.5 people and the disease would be declining and eventually stop when it gets to zero.

The flu in 1918 killed 50 million people, according to an article published in BMC Medicine, the R-value of this pandemic was estimated to be between 1.4 and 2.8.

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