Commentary on COVID-19 cases in Leicester

Leicester went into lockdown in early July, with the Statutory Instrument setting out these restrictions published on 3 July (The Health Protection (Coronavirus, Restrictions) (Leicester) Regulations 2020) just before the loosening of restrictions elsewhere in the country.

Public Health England has published an analysis of what is known about the Leiecester outbreak. Diagrams are from the PHE report.

The latest daily case numbers are available at coronavirus.data.gov and are shown below. Note that the latest figures in the data download are not complete, as these will exclude specimens in the post. Also note that the number of positive cases detected will be affected by Leicester being in the news, availability of more testing stations, and the functioning of the NHS Test and Trace service (see update below).

The first thing to note is the mismatch between testing that was disclosed to the public (so called Pillar 1 tests) when a potential lockdown was being discussed by politicians and the total number of tests being conducted (Pillar 1 and Pillar 2 tests). I have discussed why this was a problem here. Since writing, the Government has disclosed total positive tests (but not the number of tests taken) for each location, including Leicester.

Firstly, the number of positive tests rose to 23 June (the chart above updates this slide).

PHE Preliminary Investigation into COVID-19 Exceedances in Leicester (June 2020)

Since then, it appears that the number of positive tests may be falling, but this is preliminary analysis, and we shall know for sure on Thursday when PHE release their updated analysis for the whole country.

The current Leicester cases seem to be through working age people and children (this is where Leicester may be unusual – other outbreaks may be in care homes where the population is older).

PHE Report

This is the spatial analysis of where cases have taken place in Leicester (the left map is Pillar 1 testing and the right map is Pillar 2 testing).

PHE Report

And this breaks down the wards in which most cases were located

PHE Report

with the corresponding map here

PHE Report

It is important to note that testing has been increasing in Leicester, so some of the increase in positive cases may be due to this. William makes the comment below that this may be due to the location of walk-in tests making people from those areas more likely to take tests compared to other areas of the city. There is a feedback effect here, where more positive cases means more testing resources allocated to those areas which means more testing of those areas. Without test data (number of tests in each location), it is not possible to see whether the increased case density is as a result of increased numbers of tests, as we don’t know the percentage of positive cases at each location.

The latest Public Health England national report here with results shown below.

Source: http://www.duncanrobertson.com/2020/07/01/which-city-could-be-next-for-a-leicester-like-lockdown/
Source: http://www.duncanrobertson.com/2020/07/01/which-city-could-be-next-for-a-leicester-like-lockdown/

Leicester cases are now published here:
https://coronavirus-staging.data.gov.uk/cases?areaType=ltla&areaName=Leicester and here is the data from 6 July 2020

coronavirus-staging.data.gov.uk 6 July 2020 data

Update: The .gov.uk analysis seems to average out the 7-day average as +/- 3 days which is misleading, as the recent specimen date tests may not have arrived.

The threshold for lockdown is not publicly disclosed (and there is unlikely to be an absolute threshold as local considerations such as where the outbreak is taking place (for example in a factory or a care home that can be relatively well contained). However, Germany has set a threshold of 50 cases per 100,000 to consider an ’emergency brake’ and reimpose lockdown-like restrictions.

Taking the population of Leicester as 348,300, this would mean that this threshold of 50 cases per 100,000 in a week would be 50 * (348,300 / 100,000) / 7 = 25 cases per day as a threshold. Although of course, the threshold for entering and leaving lockdown are not the same. And Directors of Public Health and journalists, armed with timely and complete data, are far more able to understand what is happening at a local level.

I will provide an analysis of the Public Health England data on Thursday when it is published. For updates, please come back to duncanrobertson.com or follow me on Twitter @Dr_D_Robertson

Beware of the Survivorship Bias of Politicians: COVID-19 Letter Published in The Financial Times


The news that UK business secretary Alok Sharma has been tested for Covid-19 highlighted the issue of survivorship bias, that is the systematic overestimation of performance and underestimation of risk by ignoring non-survivors.

In the early stages of the epidemic, the risk perception of politicians broadly matched that of the general population. However, if the proportion of decision makes that have been infected by the virus and survived exceeds that of the population, the executive’s risk appetite could surpass that of the people they represent.

Politicians need to ensure that they make decisions in such a way that suvivorship bias does not affect their judgment.

Dr Duncan Robertson

School of Business and Economics, Loughborough University

Muddling Through Does Not Work for Pandemics: COVID-19 Letter Published in The Financial Times

In 1959, Charles Lindblom wrote The Science of “Muddling Through”, advocating an incremental approach to public policy and management. “Muddling through” does not work for pandemics. The science of pandemics is dominated by epidemiology, not behavioral science. The delay between policy decisions (or indecisions) and the resultant high UK death rate needs tracing back from the prime minister and his advisers to Cobra, the chief scientific adviser, and the Scientific Advisory Group for Emergencies. However, this is one form of contact tracing that can be delayed until the inevitable public inquiry.

Dr Duncan Robertson
Fellow in Management Studies,
St Catherine’s College,
University of Oxford, UK