As few as 10% of people are responsible for 80% of transmission – and that must shape how we tackle this virus
In February, when Covid-19 was just beginning to spread around the world, a single infected individual exposed as many as 1,100 people in Daegu, South Korea, possibly infecting hundreds. This “superspreading event” sparked a cluster of transmission that eventually grew to more than 5,000 cases in a country recognised as having one of the most effective Covid-19 control programmes to date.
At first glance, this seems wildly inconsistent with what we know about how efficiently Sars-CoV-2 (the virus that causes Covid-19) transmits. The average number of infections caused by someone infected with Sars-CoV-2 – a value known as R – is thought to be between two and five if there is no immunity in the population. How, then, could this one individual, known as “patient 31” by health officials, infect so many?
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