Interpretation of the Basic Reproduction Number

Maybe not the most click-enticing title, but I hope you find the actual content a bit more interesting.

“In epidemiology, the basic reproduction number (sometimes called basic reproductive rate or basic reproductive ratio) of an infection is the mean number of secondary cases a typical single infected case will cause in a population with no immunity to the disease in the absence of interventions to control the infection.”


In the marketing world, R is how many people one single person (infected by the message) will pass the message on to, on average.

“The basic reproductive rate is affected by several factors including the duration of infectivity of affected patients, the infectiousness of the organism, and the number of susceptible people in the population that the affected patients are in contact with”

– wikipedia

So, there are different variables to play around with to make something reach the threshold of 1. Here are my short interpretations:

I would interpret the duration of infectivity as how long someone actually remembers the content that we want to go viral and is able to pass it on. The quality of the content affects this, as well as if we have created incentives to come back to the content. In a way, the strongest content keeps us infected indefinitely. But, we need to know where to find the content again to be able to pass it on.

The infectiousness of the organism would also have very much to do with the quality of the content, the appeal the content has. So, we have learnt that quality content seems to be key in creating something that might have a chance to go viral.

The number of susceptible people in the population that the affected patients are in contact with would have something to do with the context you chose to seed in. A brownie recipe posted in a car forum might not spread quite as much as the latest paparazzi pictures of a new Ferrari. The car enthusiasts are simply not interested enough in a brownie recipe, even though they might enjoy eating a brownie once in a while.

Also, some people are more prone to passing things on. I am sure you have some friends that sends you stuff a little too often and some that never do. Finding environments where people who tend to pass things on gather could prove vital for a campaign.

Please comment if you don’t agree, have things to add or think you can help improve. =) I really want to understand this even better!

Kristofer Mencák has a M.Sc. in Business Administration from Stockholm School of Economics. He is a consultant, author and lecturer on social media, viral marketing and word of mouth. He has also recently been travelling the world teaching the dance kizomba.

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