The Psychology of the Virus Super-Spreader

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Sadly Dr Peter Bruggen passed away in Sept 2018 so this article was written by Dr Raj Persaud alone.

Covid-19 like many infections, can produce such mild symptoms, or maybe none at all, in some, so that they don’t realise they are infected; they then spread the contagion without realising it. This means that Covid-19 may be particularly prone to the disturbing phenomenon of the ‘super-spreader’.

An illustration that appeared in 1909 in The New York American June 20, 1909
Mary Mallon (1870-1938) nicknamed “Typhoid Mary”
Source: An illustration that appeared in 1909 in The New York American June 20, 1909

Officialdom doesn’t seem keen so far on disseminating the ‘super-spreader’ theories over Covid-19, maybe because they don’t want the general public to feel ‘off the hook’ to make mass personal changes. This may happen if they don’t feel personal responsibility for contagion; which they won’t if they can blame a few ‘super-spreaders’ instead.

But maybe the opposite is true, if the public better grasped the concept of the ‘super-spreader’, maybe they would adhere more to public health restrictions?

Why can there be such large variability between countries and regions, as to the spread and virulence of a particular infectious disease? It is tempting to see the answers in, for example, differences between varying Government policies, but there are other biological factors which can be in play as well, such as genetic susceptibility, or the age profile of a population.

However, one phenomenon which may not be receiving as much attention as it deserves, given it’s potential to explain variable rates of spread of infections, is the idea of the ‘super-spreader’.

‘Super-spreading’ refers to the frightening spectacle when just a single patient infects such a huge number of contacts, that the usual or average rate of spread from more typical individuals, becomes dwarfed.

There is a strand of thinking in epidemiology that the controversial role of ‘super-spreaders’ needs to be better understood if modelling of epidemics is to become more accurate, and official response better targeted.

‘Supers-spreaders’ might be out in the community spreading the disease for an extended period of time before being detected by conventional methods.

In a study entitled ‘MERS, SARS, and Ebola: The Role of Super-Spreaders in Infectious Disease’, the authors point to the role of so-called ‘super-spreaders’ in past epidemics.

Published in the academic journal Cell Host & Microbe, the study quotes the example of the 2015 MERS-CoV outbreak in South Korea, which began from a single case who had travelled from the Middle East. Middle East Respiratory Syndrome coronavirus (MERS-CoV) emerged as a new virus resulting in severe respiratory disease plus renal failure. The case fatality rate was up to 38%.

The authors of this study into ‘super-spreaders’ were based at the Chinese Academy of Sciences, Beijing, Shenzhen Third People’s Hospital, Shenzhen, and the Chinese Center for Disease Control and Prevention, Beijing, China.

MERS-CoV cases typically occur in the Middle East, where dromedary camels harbour the virus.

Between May and July 2015, an outbreak of MERS-CoV in South Korea killed 36 people out of 186 confirmed cases. Twenty-nine secondary infections in South Korea have been traced to a single index patient who travelled from the Middle East. Two of these secondary cases were apparently responsible for 106 subsequent infections, out of 166 known cases at the time.

So, according to this study, the MERS-CoV outbreak in South Korea was driven primarily by three infected individuals, and approximately 75% of cases can be traced back to three super-spreaders who have each infected a disproportionately high number of contacts.

This study also documented ‘super-spreading’ during the SARS-CoV outbreak in 2003. The index patient of the Hong Kong epidemic was treated at Prince of Wales Hospital and was associated with at least 125 secondary cases.

Similar events, according to the study, were observed with the 2014-15 Ebola outbreak, centred in Western Africa. In Sierra Leone, the funeral of a traditional healer that died from EBOV directly infected 13 others and was ultimately linked to more than 300 cases. The authors point out that ‘super-spreading’ has also been documented in measles and TB outbreaks.

The authors contend that initial stages of all of the outbreaks mentioned above involved at least one super-spreading event. Super-spreaders the authors argue, may become the key difference between an infection cluster and an epidemic.

In a study entitled, ‘Transmission potential of COVID-19 in South Korea’, published at medRxiv as a preprint, the authors point out that the epicentre of the South Korean COVID-19 outbreak has been identified in Daegu, where the rapid spread has been attributed one super-spreading event that has led to at least 40 secondary cases stemming from church services in that city.

In another study entitled, ‘Spatial and temporal dynamics of superspreading events in the 2014–2015 West Africa Ebola epidemic’, published in PNAS, (Proceedings of the National Academy of Sciences  of the United States of America), the authors argue that had the super-spreaders been identified and quarantined promptly, around 61% of the Ebola infections could have been prevented. The authors argue their findings highlight the key role of super-spreaders in driving epidemic growth.

While there are many factors that may explain the still mysterious phenomenon of ‘super-spreading’, individual behaviour might play a key role.

A classic example that arises from experience of previous outbreaks includes so-called “doctor shopping”. This can comprise visiting multiple hospitals to treat the same ailments, even traveling to other countries to visit new clinics.

Different health care systems may promote contrasting doctor-shopping behaviours.For example, privatised healthcare lends itself more readily to ‘doctor-shopping’, as the individual patient can decide to consult as many different physicians as they can afford. Indeed, in non-pandemic times this may be a key advantage used to promote fee-for-service systems.

Yet a more centralised, state-controlled system, like the UK’s NHS (National Health Service) is better equipped to prevent this. In the NHS you can’t very easily consult any other Family Practice, beyond the one you are registered with. Also, you can’t see any specialist you desire, unless you have been formally referred by your General Practitioner.

During normal times these limitations might be irritating, but in a pandemic these restrictions may curtail ‘super-spreading’.

However, it is not clear that any healthcare system, no matter how well organised, can do much against an extremely determined ‘super-spreader’, unless extremely draconian powers of incarceration are invoked.

This is precisely what happened in the case of perhaps the first documented case, and most famous individual ‘super-spreader’ in history, an Irish immigrant cook who disseminated Typhoid fever in the New York area, subsequently becoming notoriously referred to as ‘Typhoid Mary’.Her story is important as it may be a prophetic foretelling of our own future. It could be many recalcitrant spreaders who refuse to conform to public health advice, may yet find themselves similarly imprisoned.

Between 1900 and 1907, Mary Mallon moved as cook from household to household, infecting some 22 people with typhoid fever. At this time this was a disease with a ten-per-cent mortality rate.

Several attempts were made to enlist her cooperation in being tested, and to comply with quarantine advice, which she resolutely ignored. Eventually the authorities concluded that she represented such a threat to the public’s health, she had to be incarcerated, and therefore isolated against her will on a quarantine island in the East River.

The police and doctors were involved in the frantic physical chase to capture her. Such was the struggle from the intransigent cook, that the doctor had to be involved in the forcible physical restraint involved in subduing the patient in the ambulance, removing her from her freedom.

Mary Mallon was released over three years later having grudgingly promised to comply with restrictions, including promising not to return to cooking, and signing in regularly with the authorities.

However, such was her actual resolution to return to cooking against medical advice, she eventually slipped away again from surveillance, only to resurface 5 years later, when she was discovered to be cooking at the Sloan Maternity Hospital in New York City, where 25 new cases of typhoid fever had just been reported.

One lesson that might be learned from her case was that finding her alternative viable employment might have prevented the second tragic outbreak.

Mallon was sent back to her secluded bungalow on North Brother Island, for the rest of her life. She died on Nov. 11, 1938, after more than 26 years of compulsory isolation. In the end, she had infected at least 51 people, 3 of whom died.

Yet as Janet Brooks points out in her investigation entitled, ‘The Sad and Tragic Life of Typhoid Mary’ published in the Canadian Medical Association Journal, by the time she died, New York health officials had identified more than 400 other healthy carriers of Typhoid, yet no one else was forcibly confined.

Was Mary Mallon discriminated against? Was it something to do with being an Irish single woman with no husband nor parents to fight her corner, or did she suffer from some kind of intransigent personality type, or even disorder, which meant she was more prone to conflict with the authorities?

Could this personality type identify behavioural super-spreaders today?

Before they imprisoned her, Mary Mallon was quick to wield a carving fork whenever approached by health officials who first tried to reason with her. Once incarcerated she wrote violently threatening letters to her doctors, explaining that if ever released, she would get a gun and kill them. This was not an immediately obviously sensible tactic over securing her freedom, and might suggest the possibility of an undiagnosed mental illness.

Author Susan Campbell Bartoletti, in her biography of Mary Mallon, entitled, ‘Terrible Typhoid Mary – The Deadliest Cook in America’, points out that she could have been let out of her imprisonment much earlier, if she had just played the politics, and agreed to the terms the authorities demanded, from the beginning.

She could have simply agreed not to cook, and she could then have slipped away from their surveillance, once released. Her problem really was that she was too honest.

Paradoxically could extreme sincerity might also be a sign of a psychiatric disorder? It was the key argument many anti-psychiatrists in the 1960’s deployed against the incarceration of psychiatric patients, which is that they landed themselves in trouble because they were too ‘authentic’ or honest when answering the doctor’s questions.

This is one of the underlying themes of films like Jack Nicholson’s ‘One Flew Over The Cuckoo’s Nest’.

If it was her persistent personal rigidity, in denying there was anything wrong with her cooking, maybe Mary Mallon could not apparently grasp the concept of being a ‘healthy carrier’, which trapped her into dogged conflict with the authorities, and left her to languish for the rest of her life in enforced quarantine.

Maybe there seemed to be a pride issue involved in that she may have regarded Typhoid as a disease associated with being ‘dirty’, with not washing her hands properly after leaving the toilet before cooking, yet she was a proud ‘clean’ cook. Perhaps the doctors failed in their attempt to explain the science to a scarcely educated kitchen worker because of the cultural and class divide between them?

Maybe they are failing again with the public as they are making the same mistake in not grasping how to bridge the chasm in understanding between the epidemiologists and the public?

Or is there, in fact, a little of Mary Mallon in all of us who buck the Government’s injunctions? We rebel when attempts are made to prevent us from doing what we love, because we don’t see the link between our own personal behaviour, and how it’s going to stop a pandemic?

The story of possibly the first documented ‘super-spreader’ in history, suggests that even today, a failure to grasp the science behind infections and disease, by just one person, could prove deadly to society.


MERS, SARS, and Ebola: The Role of Super-Spreaders in Infectious Disease. Gary Wong, Wenjun Liu, Yingxia Liu, Boping Zhou, Yuhai Bi, George F.Gao Cell Host & Microbe Volume 18, Issue 4, 14 October 2015, Pages 398-401


Transmission potential of COVID-19 in South Korea. Eunha Shim, Amna Tariq, Wongyeong Choi, Yiseul Lee, Gerardo Chowell. medRxiv preprint doi:


‘Spatial and temporal dynamics of superspreading events in the 2014–2015 West Africa Ebola epidemic’. Max S. Y. Lau, Benjamin Douglas Dalziel, Sebastian Funk, Amanda McClelland, Amanda Tiffany, Steven Riley, C. Jessica E. Metcalf, and Bryan T. Grenfell. PNAS February 28, 2017 114 (9) 2337-2342


Typhoid Mary: Captive to the Public’s Health By Judith Walzer Leavitt ISBN 0-8070-2102-4, Beacon Press, Boston, Massachusetts


The sad and tragic life of Typhoid Mary. J Brooks. CMAJ. 1996 Mar 15; 154(6): 915–916.

‘Terrible Typhoid Mary: A True Story of the Deadliest Cook in America’ by Susan Campbell Bartoletti. Houghton Mifflin Harcourt Publishers.

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