How to spot a
They’re responsible for 80% of cases and are the key to stopping corona. No wonder scientists are racing to work out . . .
With Covid cases on the rise, it’s clearly very important to identify what’s driving this second wave. is it students socialising at university? Or is it people packing into bars?
it’s probably a bit of both, but there i s mounting evidence that the main driver is a small group called ‘superspreaders’.
they may not have symptoms but still manage to infect lots of others. in reality, relatively few people are responsible for the majority of cases.
A striking example of a superspreader was 53-year-old Steve Walsh, who at the start of the UK outbreak managed to unknowingly infect at least 11 others.
he got infected at a conference in Singapore and then went skiing. he infected most of the people in his chalet but what was surprising is they didn’t then go on to infect many others. in fact, a nine-year-old boy in the party who later tested positive for the virus, did not pass it onto anyone else, despite coming i nto close contact with more than 170 people over the following days before he was identified.
this is not a fluke. it seems that 80 per cent of new cases are caused by just 10 per cent of infected people — most people who get Covid-19 never give it to anyone else.
i f we can i dentify t he superspreaders and isolate them quickly, it a cook again. But she just changed her name and went on working. She was finally caught, a few years later, cooking in a hospital where a typhoid outbreak led to 25 people being infected, and two dying. Mary was arrested and confined until her death, 23 years later.
to our modern sensibility this is inhumane, but clearly the major difference is that isolating a Covid superspreader would last days, perhaps weeks, not years — if track and trace can spot them.
But rather than identifying individuals, the key may lie in reducing superspreader events. these are one- off gatherings where lots of people get infected.
it could be a pub, like the one in Aberdeen where 13 people tested positive; or a chummy meeting of Right-wing U.S. politicians, presided over by Donald trump, which led to seven cases.
Central to the idea of superspreader events is a new understanding about the virus — just as important as the R rate ( how many people someone typically infects), is the ‘K value’. this is the pattern in which the virus spreads. With infections such as flu, the K value is one — it spreads evenly, each infected person typically passing it on to one other.
the K value for Covid is lower