Following the hospitalisation of US President Donald Trump with COVID-19, an event held at the White House in the preceding week is being investigated as a possible “super-spreader” event as a growing number of people at the event test positive for the virus. (1)
But exactly what does this phrase mean and what is its significance?
There is no clear definition for the term ‘super-spreader’ or ‘super-spreading event’. The World Health Organization refers to a super-spreader as a person or an event that transmits infection to a larger number of individuals than expected as estimated by the basic reproduction number. (2)
(Click here to read more about the reproduction, or R, number).
There are many theoretical explanations for the occurrence of super-spreading including increased viral load in some people, the occurrence of asymptomatic individuals who spread it unwittingly and extensive social interactions that allow the virus to spread rapidly. (3)
“Typhoid Mary” is one of the world’s most famous super-spreaders, a woman who in her work as a cook in the 19th century spread typhoid across the USA to seven out of eight families she worked for whilst remaining well herself. (4)
Super-spreaders have been identified for COVID-19. A Hong Kong study estimated that 80% of cases in Hong Kong came from just 20% of the infected people. (5)
This phenomenon makes it hard to predict when an increase in cases might occur because one super-spreader, either person or event, can be responsible for a sudden surge in cases.
This is not a new phenomenon. SARS and MERS, both illnesses also caused by coronaviruses, behaved in a similar way. In both their outbreaks clusters of infection were traced to super-spreaders at close gatherings. Social events attended by super-spreaders can quickly undo the effects achieved through lockdown. (6)
Unfortunately there is no way of knowing if someone is a super-spreader. Many are asymptomatic and scientists do not yet understand why some people are affected in this way. Super-spreaders are only identified by tracing backwards through a disease outbreak and can lead to stigmatisation of the person involved as happened in the UK when the press named a man identified as a super-spreader. (7) (8)
In March 2020 in rural India a religious leader recently returned from Italy did not follow the self-isolation rules on his return and instead went straight to Punjab state where he preached in around 20 villages both outdoors and in people’s homes. He died from COVID-19 on 18 March 2020. Dozens of villagers became infected through their contact with him as did 19 members of his own family. 30 people died and a total of 40,000 people in the villages were placed in strict quarantine for 21 days. (9) (10)
In March 2020 in Canada, a visiting pastor from Singapore triggered a COVID-19 outbreak when he was guest speaker at a prayer meeting for 25 people. Ten people were infected at the meeting, four of whom became critically ill with one dying. A total of at least 34 cases were linked to that event when some of the people at the meeting in turn passed it onto their families. (11)
The top US virus expert Dr Anthony Fauci has described the event held at the White House on 26 September 2020 as a super-spreading event. At least 11 people who attended the event and 34 White House aides and staff tested positive in the week following the event.
Dr Fauci said, "The data speak for themselves - we had a super-spreader event in the White House, and it was in a situation where people were crowded together and were not wearing masks." (12)
People with a high viral load and large, crowded events both pose the biggest infection risks to others. Combine the two and the risk of disease transmission increases dramatically. With no way to identify the person who is a super-spreader, mitigation has to be aimed at the crowded places and events. Lockdowns and closure of public places aim to reduce or stop interactions between people, thereby disrupting and removing opportunities for the virus to spread. (13) (14)
As cases increase rapidly again across most of Europe lockdowns are being re-introduced in many countries. Europe (including all of Russia) accounts for just under 10% of the world’s total population and has recorded 16% of the world’s total COVID-19 cases and 21% of the total deaths.
Both cases and deaths in the USA are the highest in the world and continue to rise, accounting for more than 25% of the worldwide totals. In the run-up to the US Presidential election, with huge, crowded rallies taking place both indoors and outdoors and little or no mitigation being taken against the risk of COVID-19, that 25% is likely to increase. Given the fact that the USA accounts for just 4% of the world’s total population that is a sobering thought. (15) (16)
