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The 2020 - 2021 Coronavirus Pandemic in the UK

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The course of the coronavirus pandemic in the UK is shown below in a single chart summarising key metrics downloaded from the UK coronavirus Dashboard.

The data may also be visualised as an animation.

Some values reported on the daily Dashboard are provisional and subject to revision over time; more stable data is available from the download section of the Dashboard a week or so later. In the chart weekly values have been scaled by Z-score normalisation (whereby the mean of each data series, Mean[D], is subtracted from each value in that series, d, the result being divided by the standard deviation of the series StdDev[D]). As can be seen most values fall within two standard deviations of the mean. The chart and discussion are updated regularly.

The Current Situation

The highly infectious Delta variant is the dominant coronavirus strain in the UK and, ominously, the Omicron variant has now reached us. After a dramatic increase in July 2021, the number of infections reported daily levelled off then fell somewhat, but has now risen above July's level again. Hospital admissions and deaths from Covid remain fairly high, but appear to be falling slowly. Fortunately the vaccination campaign appears to be mitigating the severity of the present wave, so far.

We are by no means out of the wood yet and it is going to be another hard winter. What is to be done?

Z-Score Standardised UK Weekly Data reported for the weeks ending 29th February 2020 to 29th November 2021


Data Series Chart Symbols Weekly data series description Weekly Minimum Weekly Maximum Latest Reported
Virus Tests Conducted [dotted blue line] Number of PCR and Lateral Flow tests processed. 67,469 [ 04 Apr 20 ] 8,617,650 [ 13 Mar 21 ] 6,541,574
Confirmed Cases [dotted red line] Number of positive tests reported. 183 [ 07 Mar 20 ] 417,620 [ 09 Jan 21 ] 307,979
% of Positive Tests [solid red line] Percentage of the tests reported as positive. 0.2% [ 1 May 21 ] 12.5% [ 2 Jan 21 ] 4.7%
Hospital Admissions [solid yellow line] Number of patients admitted to hospital 693 [ 22 Aug 20 ] 28,761 [ 16 Jan 21 ] 5,709
Deaths [solid black line] Number of deaths within 28 days of a positive test 2 [ 07 Mar 20 ] 8,739 [ 23 Jan 21 ] 858
R [see note] [smoothed green line] The ratio of the percentage of positive tests adjusted for the number of tests per week in successive weeks

- Coronavirus testing and hospital admission data are not available for March 2020.
- The weekly percentages of positive tests are shown from May 2020 onwards.
- Patient hospital admissions are generally reported a few days later than the rest of the data.
- The reproduction number R, which is an approximation, has not been standardised.

Testing and the number of confirmed cases

The number of people testing positive each week [dotted red line] surged in September and October 2020 and again very rapidly in December 2020 and January 2021. However, this does not take into account the number of PCR and Lateral Flow tests recorded [dotted blue line], which increased from around 110,000 per week in early April 2020 to over eight million per week by mid-March 2021. The percentage of positive tests [solid red line], shown from May 2020 onwards, is a better metric, assuming that those tested are a consistently representative sample of the overall population.

Hospital admissions and deaths

During the first wave of coronavirus infections the weekly percentage of positive tests and the number of hospital admissions peaked in mid-April 2020, followed by a peak in deaths a couple of weeks later. A similar but less alarming trend which developed in October 2020 was somewhat mitigated by the four-week lockdown ending on 2nd December. Then the number of infections, hospital admissions and Covid-related deaths soared and it was clear that the more infectious variants of Covid were getting out of control. The effects of the January 2021 lockdown and the successful vaccination program are now apparent, the proportion of positive cases to the numbers of hospital admissions and deaths fell consistently during February, March and April 2021 but have now risen again significantly.

Reproduction number R

For the purposes of this summary the reproduction number, R, the average number of secondary infections produced by a single infected person, plotted as a smoothed solid green line on the chart] has been estimated as the ratio of the percentage of positive tests adjusted for the overall number of tests in successive weeks. This value may 'bounce around', with the ratio changing noticeably from week to week, particularly when the number of cases is low, the trend over a month or so being more meaningful. The first lockdown in March 2020 resulted in a decrease in R, followed by a slow increase during the summer when infections were low. In September 2020 the general trend was a more rapid rise, followed by a slow decline during the November 2020 lockdown and a more rapid rise in the run up to Christmas. After falling in January and February 2021 R has risen remorselessly until very recently and remains higher than 1.0.

Overall number of infections

The Imperial College REACT immunoassay study of 109,000 randomly selected participants in England conducted between 20th June and 13th July 2020 estimated that around 3.3 million people, approximately 6% of the population of England, had antibodies to SARS-CoV-2 by the end of June 2020, the overall infection fatality ratio being 0.90%. The proportion of the population who have contracted the virus is now significantly higher, probably by a factor of four or more. Modelling reported in The Guardian [11th January 2021] suggested that over 12 million people in England had been infected by that date. A further 7 million positive tests have been reported since then.

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© Chris Newall 2021

Author : Chris Newall
Page created on : 12th October 2020
Last updated on : 29th November 2021