The total number of positive results for NHS and commercial Covid-19 tests is more than double the generally reported figure for people with confirmed Covid-19
And even the real figure for confirmed Covid-19 cases is just the tip of the iceberg
Commenting on the publication of Calderdale’s outbreak prevention and control plan, Deborah Harkins, Calderdale Council’s Director of Public Health warns:
“Unfortunately it is highly likely that we will remain at risk from the coronavirus for at least the next 12 months so as lockdown eases it’s vitally important that we do all we can to control the spread of infection and keep people safe.”
And Calderdale Council’s Leader, Cllr Tim Swift, says
“The most important thing… is for us all to play our part in reducing the risk of transmission. We should continue to stay at home as much as possible, regularly wash our hands for at least 20 seconds and maintain social distancing whenever we are in contact with other people.”
Under-reporting of confirmed cases
The under-reporting has occurred because – until this morning (July 3rd) – the government’s Coronavirus data tracker only included results from tests carried out in NHS hospitals for those with a clinical need, and health and care workers. These tests are analysed in Public Health England labs. (So-called Pillar 1 tests.)
Until today, the government’s data tracker omitted the results of commercial tests for anyone with Covid-19 symptoms, that are carried out at drive through sites or at home, with the results analysed at commercial labs. (Pillar 2 tests.)
Since I wrote this blog post yesterday – based on a 30th June post on Calderdale Covid-19 Action Group – overnight the government has started reporting the complete numbers of confirmed Covid-19 cases – both Pillar 1 and Pillar 2.
They have corrected all the historical data, going back to the start of the outbreak, so there is now no record of their earlier erroneous figures.
“The government is now following the home office playbook for stories about immigration cases – deny it strongly then fix it fast”
As part of the government’s Covid-19 data tracker update process, the number of total reported UK-wide cases has fallen by around 30,000 and now stands at 283,757.
This is because the government have removed duplicates within and across pillars 1 and 2, so that a person who tests positive is only counted once. This was anticipated, thanks to reporting from @BBCMoreOrLess.
Confusingly, until today, the data tracker SAID it included commercial as well as public tests in its total number of lab tests carried out (313,483 by 2nd July). But there was a crucial caveat:
“Includes tests carried out by commercial partners which are not included in the 4 National totals“. (our bold italics)
Those national totals only gave results for 197,246 tests (if my arithmetic is correct, adding up the 4 national totals). These are the Pillar 1 (NHS) test results.
This meant when you look at the confirmed Covid-19 cases for local authorities, which come under the National totals, you were only getting the number of Pillar 1 (NHS) positive test results.
For Calderdale, on July 2nd that was 306 – up one from the day before.
This gives a misleadingly low impression of confirmed Covid-19 cases in Calderdale, with the risk that this might create a false sense of confidence that the pandemic is on the way out.
Taking Pillar 2 (commercial) test results into account more than doubles the number of confirmed Covid-19 cases in Calderdale
The total number of Pillar 1 and Pillar 2 test results is given in the Public Health England WeeklyCovid19 Surveillance Report, week 26 . This states (p 2) that as of 9am on 24 June 2020, a total of 238,911 people had been confirmed positive for COVID-19 in England, through Pillar 1 and 2 tests.
The number for Calderdale can be derived from a map in the weekly covid 19 surveillance report week 26. The map shows rates of infection per 100k population, based on pillar 1 and pillar 2(commercial) tests. The Calderdale rate is 260-313 per 100k population.
Multiplying the Calderdale rate by 2.1 (because Calderdale has 210,000 pop), gives 546-657 confirmed Covid-19 cases. That’s how I figure Calderdale has around double the reported number of confirmed Covid19 cases (reported as 306 on 2nd July).
The corrected numbers published by the government today show I was spot on
Confirmed cases in Calderdale are now recorded as 653, and the cumulative rate of infection per 100K population is 310.8 – info source here: https://coronavirus.data.gov.uk/#category=utlas&map=rate
Around 25 new Calderdale Covid 19 cases confirmed during 3rd week in June
There were 12 confirmed Covid-19 cases per 100K population in Calderdale during the period covered by Public Health England’s Weekly surveillance report week 26 (based on data between 15 June and 21 June 2020, and where available daily data up to 24 June 2020.)
This is shown in the latest weekly Covid-19 datasheet for all local areas, collated by the Financial Times journo John Burn-Murdoch from the Public Health England report.
By my arithmetic, this amounts to 25 people (2.1x 12 per 100k population) confirmed as Covid19+ during that week.
This is shown in the Financial Times map based on the same PHE data:
Around 31 new Calderdale Covid-19 cases confirmed week ending 24 June
Data from the latest Public Health England Covid-19 weekly report (week 27) show that confirmed Calderdale Covid-19 cases are up by 19% this week. Kirklees down by 13%, Bradford down by 34%.
For Calderdale, in the week ending 24 June there were 14.8 confirmed cases per 100k population, amounting to 31 people (14.8 x2.1).
Confirmed Covid-19 cases are only the tip of the pandemic’s iceberg
The Calderdale Covid-19 Outbreak Prevention and Control Plan states (3.5)
“Studies … suggest that nationally, only approximately half of people with symptoms suggestive of COVID-19 are reporting them to the national NHS Test and Trace system. We need this to be much higher in Calderdale…”
The Cambridge University Medical Research Council Biostatistics Unit and the Office of National Statistics both estimate that the cumulative number of people infected with Covid-19 in England is far higher than the 238,911 people reported by Public Health England on 24 June.
The Cambridge Biostatistics Unit’s Covid-19 “nowcasting” estimate is that up to 1st July 2020 around 5,160,000 people have been infected with Covid-19. (This is with a 95% Credible Interval 4,200,000–6,880,000).
To make this estimate, they fit a transmission model (Birrell et al. 2016) to a number of data sources (which are listed on their now-casting webpage ), to reconstruct the number of new COVID-19 infections over time in different age groups and NHS regions.
Results from the most recent (13 June 2020) Office for National Statistics antibody sampling indicate 3 million people in England have had the disease.
The wide variation between the Biostatistics Unit’s now-casting estimate and the ONS anti-body sampling estimate shows the difficulty of assessing how many people in England have been infected by Covid 19.
But both indicate that the incidence of Covid-19 is far higher than the number of confirmed Covid-19 cases. This is not surprising, since testing Covid-19 symptomatic people in the general population only started a few weeks ago. And many people are infected with Covid-19 without showing any symptoms.
The lack of adequate data about the scale and whereabouts of Covid-19 infections makes the task of preventing and controlling its spread immeasurably harder than it would have been if, from the start, government had followed World Health Organisation advice to “test, test, test.”
Reblogged from Upper Calder Valley Contact Tracing