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One-in-five people across England may have had coronavirus, new modelling suggests, equivalent to 12.4 million people, rising to almost one in two in some areas.
It means that across England the true number of people infected to date may be five times as high as the total number of known cases according to the government dashboard.
However, in some parts of the country, the disparity may be even greater, with parts of London and the south estimated to have had up to eight times as many cases as have been detected to date.
The analysis, by Edge Health, reveals that the total number of actual coronavirus infections in England could be as high as 12.4 million – equivalent to 22% of people across England – as of 3 January.
Cases detected through the government’s test and trace programme stood at 2.4m on the same date in England.
The model estimates an area’s number of cases by comparing the number of deaths in the area against an estimated infection fatality rate. It assumes that there is a three-week lag between a recorded cases and any associated death.
The results suggest that more than 10% of residents in 138 of England’s 149 upper tier local authorities have contracted the disease according to the estimates.
In some areas the cases are even higher. The model suggests that two in five people have been infected in six London and south-eastern local authorities: Barking and Dagenham, Newham, Thurrock, Redbridge, Havering and Tower Hamlets.
The London boroughs of Barking and Dagenham and Newham are each estimated to have had well over 100,000 coronavirus infections each, around 54.2% and 49% of their populations respectively.
Official figures from Public Health England show that just under 14,700 cases had been recorded in Barking and Dagenham and just under 21,700 in Newham by 3 January.
According to the model, four north-western local authorities, which were hit harder at the start of the pandemic’s second wave, were among the 10 worst-hit local authorities: Liverpool with 38.8% infected, Manchester at 38.6%, Rochdale at 38% and Salford at 37.8%.
The estimates are in keeping with the accepted knowledge that the actual number of infections is likely to be far higher than the number of recorded cases because of asymptomatic cases and testing failing to pick up every case. This is especially true at the start of the pandemic when the UK’s testing regime was far poorer.
Official government data on recorded cases to date shows Merthyr Tydfil, Blackburn with Darwen and Blaenau Gwent as having the highest rates of recorded cases. However, the new estimates suggest the published case figures are far lower than the “real” level of infection.
Daily testing capacity stood at below 40,000 for the first half of April, while it now is over 500,000.
The modelling suggests that Newham, Reading and Barking and Dagenham each have seen almost eight times as many infections as official recorded figures show.
Estimated cases are more than five times the official count in 77 areas of England – just over half the 149 upper-tier local authorities analysed.
George Batchelor, co-founder and director of Edge Health, which produced the modelled data, said: “Reported tests are only a fraction of the picture of total infections, which show how badly hit London and the north-west have been during the pandemic. It is incredible that the level of understanding of where and how infections are occurring is not greater at this stage, since it would allow control measures to be more targeted.
“Even with imminent vaccinations, it is crucial to develop this understanding so that future variants of the virus can be effectively controlled and managed.”
The areas with the lowest estimated total infection rates are all in the south-west: Devon (5.9%), Dorset (5.8%) and Cornwall (4.8%).
Edge Health estimated total cases by looking at each local authority’s Covid-related deaths (as published by the ONS) and their estimated infection fatality ratio (IFR).
The IFR is calculated by looking at a local authority’s age profile and applying age-specific infection fatality ratios from University of Cambridge research. These infection fatality rates are slightly lower for the second wave.
Once these two metrics are known, the researchers can estimate the number of cases on any one day by scaling the number of deaths in 18 days’ time (used here as a standardised time period between recorded infection and death) by an area’s estimated infection fatality ratio. The modelled number of cases is then extrapolated forward to the present by assessing how test positivity rates have changed over the last three months.
While the modelling takes into account an area’s cases, deaths and age structure, it does not look at other factors such as deprivation.
Karl Friston, professor of imaging neuroscience at University College London and a panellist on the Independent SAGE group with special responsibility for modelling, said: “Roughly speaking, the number of new cases per day is between four and eight times the number of confirmed cases.”
UCL’s own modelling had a strong correlation with Edge’s results, leading Friston to say there was “pleasing consilience” with the two models.
Source: The Guardian
Keyword: One in five in England have had Covid, modelling suggests | World news