Party to remember: superspreader events could make Covid endemic

Researchers from Imperial College London have developed a mathematical model that can inform policies on how to prevent superspreader events.

This comes as SA faces the threat of a second wave, fuelled by community transmission in everyday activities and superspreader events.

The most recent events to grab the attention of local epidemiologists were two parties attended by University of Fort Hare students at which protocols were not followed.

So far, more than 30 students – mostly from the nursing science and law faculties – and two staff members have tested positive, while almost 1,000 others are awaiting their results.

The Eastern Cape health department issued a statement saying “allegations of noncompliance to alert level one regulations” were behind the superspreader events.

These included “masks not being worn, social distancing not being observed, and non-washing and non-sanitising of hands”. 

The first alleged superspreader event was at a tavern in Quigney, East London, on October 3, and the second was a week later, also in Quigney.

Earlier this month, a night of cheap booze on offer at the Tin Roof club in Claremont, Cape Town, also culminated in a superspreader event that has seen upward of 80 people testing positive – many of them matriculants scheduled to begin their final school examinations.

The researchers from Imperial College London looked at the “fundamental mathematical relationship between the number of people in contact with an infectious individual, the time for which they are in contact and the risk of transmission per unit time”, says researcher Dr Caroline Colijn.

It is assumed that an infected individual, particularly one with a high viral load, may interact with different groups of people over the course of the night.

The longer that person is at the venue, the more their infection is spread through actual droplets, or through aerosols (tiny particles that remain airborne).

The risk of transmission per unit time is increased exponentially by poor ventilation and crowding.

One person with a high viral load infects others with a high viral load, and those people, in turn, become superspreaders.

The researchers say “distancing of one metre or more significantly reduces transmission, and greater distances reduce it further”.

At a superspreader event in a bar or club like The Tin Roof, a distance of one metre or more between patrons becomes virtually impossible.

Another researcher, Pablo Beldomenico, from the National University of Litoral in Argentina, said “cascading superspreader events” were also possible: one person with a high viral load infects others with a high viral load and those people in turn become superspreaders.

“Cascading superspreader events might emerge if infections caused by superspreaders are more likely to be highly infectious. The mechanism suggested for this is related to viral loads.”

The SA superspreader events come in the wake of other such events across the globe, as Europe and the US battle ever-growing numbers of cases.

In Switzerland, there is growing concern after a yodelling event has seen upwards of 1,200 new infections appearing in one canton that before had been spared the high numbers.

In the US, alarms have been raised that the White House itself is in the eye of the storm.

After a reception was held for Supreme Court nominee Amy Coney Barrett, at least 12 clusters of infection have appeared – all of which have been attended by people who have tested positive and who also attended the Coney Barrett reception.

Retrospective studies on superspreader events during the earlier months of the year have also shed light on the role they play.

Cascading superspreading events might emerge if infections caused by superspreaders are more likely to be highly infectious.

In Hong Kong, one of the largest clusters earlier in the year, which culminated in 106 confirmed positive cases, was traced back to a group of musicians who had performed at four different Hong Kong bars.

The original source could not be determined, but in this cluster event, about 40 customers, 20 staff and 15 musicians were directly infected.

They then spread the infection to family, as well as work and social contacts.

According to Prof Morten Sodemann from the University of Southern Denmark, superspreader events are what could lead to Covid-19 becoming endemic.

Writing in The Conversation, he stated: “It appears that clusters of transmission from one person to a potentially large group are particularly important to maintaining the virus’s spread. In fact, these so-called superspreader events could be so significant that – without highly effective testing and contact tracing – they could cause Covid-19 to become a constant feature of our lives, even if case numbers are brought to manageable lows.”