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 is 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.
The researchers also showed the people who produced the most droplets (i.e. the potential superspreaders) tended to be older, with a higher BMI (body mass index). In other words, someone like Donald Trump. This group are not only more vulnerable to the virus, but it seems more prone to spread it if infected
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 into 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.
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
If we can identify the superspreaders and isolate them quickly, it could have a big impact on the spread of Covid.
So is there something unusual about the people who become superspreaders? In a fascinating experiment, researchers from Harvard University in the U.S. took 74 healthy volunteers and measured their breath over two days, counting how many tiny droplets they breathe out.
They found seven individuals, ie roughly 10 per cent, who produced far more droplets than the others.
The researchers also showed the people who produced the most droplets (i.e. the potential superspreaders) tended to be older, with a higher BMI (body mass index). In other words, someone like Donald Trump.
This group are not only more vulnerable to the virus, but it seems more prone to spread it if infected. So, beyond the fact that they’re likely to be older and heavier, how can you identify a superspreader?
At the moment the only way is with track and trace. This means doing lots of testing and then tracking back contacts to see who’s been doing the infecting.
While researching my recent book on the coronavirus, I came across the story of the original superspreader, ‘Typhoid Mary’, who seeded outbreaks of typhoid fever in New York and other parts of the U.S. in the early 1900s.
Typhoid, which is caused by a salmonella infection, used to be a major killer in crowded cities until sanitation improved.
During an outbreak in New York in 1907, the daughter of a rich industrialist died and he hired a researcher to find out why. This researcher discovered that a woman called Mary Mallon who’d worked as a cook in their house had also worked in other houses where people had subsequently got typhoid.
Although Mary had no symptoms, when doctors examined her poo it had lot of salmonella bacteria. Mary was a carrier, and in a time before antibiotics, there was nothing to cure her.
To protect the public she was confined to a