May 19, 2020

expert reaction to preprint estimating the overdispersion in COVID-19 transmission using outbreak sizes outside China

A preprint, a non published paper posted on Wellcome Open Research, estimated the overdispersion in COVID-19 transmission using outbreak sizes outside China.

Prof Rowland Kao, Sir Timothy O’Shea Professor of Veterinary Epidemiology and Data Science, University of Edinburgh, said:

“This analysis highlights that there is a substantial variability in the outcome of individual outbreaks of COVID-19 across many countries.  In the model the authors use, it is assumed that the distribution of outcomes for each infection follows the same pattern in all outbreaks across all countries.  While this is an important first step, it is unknown how much differences between countries might contribute to this variation.  Should this contribution be small compared to the variation in infectiousness of individuals, then this study could provide valuable insight into the potential efficacy of targeted control measures.”

Prof Paul Hunter, Professor in Medicine, UEA, said:

“The findings of this analysis are not that surprising, but do reinforce the importance of so called “super-spreading events”.  The role of super-spreading was shown quite clearly in the 2002/3 pandemic of SARS.  In the current pandemic, the most dramatic event was the cluster in South Korea associated with the Shincheonji Church that effected some 4400 people after a single individual continued to attend church whilst symptomatic.  Whether an individual becomes a super-spreader depends in part on how infectious they are and in part on how many opportunities they have to pass the infection on to other people.  Endo and colleagues state “As most infected individuals do not contribute to the expansion of transmission, the effective reproduction number could be drastically reduced by preventing relatively rare superspreading events”.  However identifying super-spreading events in advance will rarely be easy.  What this means as the UK moves into the next phase of the epidemic with “test, tract and trace” is quite clear.  However, whether we identify infected individuals by app or by contact tracing, we must ensure that as few people as possible fall between the cracks in the system.  A single super-spreading event triggered by an individual that was missed in contact tracing could easily trigger a whole new wave of infections in their locale and possibly more widely.  We must make sure this does not happen.”

Preprint (not a paper): ‘Estimating the overdispersion in COVID-19 transmission using outbreak sizes outside China’ by Akira Endo et al is posted on Wellcome Open Research.

https://wellcomeopenresearch.org/articles/5-67

All our previous output on this subject can be seen at this weblink:

www.sciencemediacentre.org/tag/covid-19

Declared interests

None received.