An investigation is underway after nearly 16,000 cases of the coronavirus have gone unreported in England, delaying contact tracing efforts.
Downing Street said there was a “technical glitch” when positive test results were transferred from labs to central dashboards.
Public Health England said 15,841 cases between September 25 and October 2 were excluded from the daily UK case counts.
Those who tested positive have been notified, but not their close contacts.
Experts advise that, ideally, contacts be traced within 48 hours.
The issue has been resolved, PHE said, with outstanding cases being forwarded to tracers at 1:00 a.m. BST on Saturday.
The Prime Minister’s spokesperson said the issue was “quickly resolved” and the NHS Test and Trace and PHE were “urgently contacting” all cases, with additional contact tracers being used.
However, he said an investigation had been opened into why the issues had not been resolved sooner.
The technical glitch means the daily totals of cases reported on the government’s coronavirus dashboard over the past week have been lower than the actual number.
BBC health editor Hugh Pym said the daily figures for the end of the week were “actually closer to 11,000”, rather than the roughly 7,000 reported.
The work has described the glitch as “shambolic”.
This was caused by some data files exceeding the maximum size and by data transfer issues between NHS Test and Trace and PHE.
Health Secretary Matt Hancock is due to brief Parliament on Covid-19 on Monday afternoon.
Prime Minister Boris Johnson said case data had been ‘truncated’ and ‘lost’, but added all people who tested positive had been contacted, with tracers ‘now working through all contacts’ .
Public health officials in the North West of England told the BBC that a significant proportion of the unreported cases originated in the region.
Cities like Liverpool and Manchester already have one of the highest infection rates in the country, at around 10 times the national average.
A BBC analysis found that the number of cases reported for the week to October 1 rose 92.6% in the North West after passing the missing tests – with similar increases reflected across England.
The increase, to 8,348 cases, is mainly due to missing tests, but the figures also include some results that came back after October 2.
At a time when the testing system comes under scrutiny after reports of delays and a system struggling to keep up with demand, the latest revelation could not have come at a more inconvenient time for the government of Westminster.
Since the nearly 16,000 additional positive test results had not been entered into the test and tracing system, their recent contacts were not immediately followed up.
Officials say the technical issue has been resolved, with all new cases added to the totals reported over the weekend.
But all this will do little to improve public confidence in the testing system in England.
And it confuses things for policymakers and officials trying to track the spread of the virus at what the prime minister has called a “critical moment.”
The government’s coronavirus dashboard on Sunday said that as of 9:00 a.m. BST there had been 22,961 more lab-confirmed coronavirus cases in the UK, bringing the total UK case count to 502,978 .
33 other people are said to have died within 28 days of testing positive for Covid-19 on Sunday.
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Public Health England acting chief executive Michael Brodie said a ‘technical issue’ was identified overnight Friday, October 2 as part of the process of transferring positive results from the Covid-19 lab to tables report board.
He said the majority of the unreported cases had occurred in the “last days”.
“We fully understand the concern this can cause and robust new measures have been put in place as a result,” he said.
PHE said NHS Test and Trace has ensured there are enough contact tracers and is working with local teams to ensure they also have sufficient resources to be able to urgently contact any cases.
The number of call attempts increased from 10 to 15 in 96 hours.
There have been obvious issues with the government’s Test and Trace data, but they don’t change our view of the UK’s trajectory.
Cases jumped in early September, they can still climb, but not as quickly as expected just a few weeks ago.
This perspective comes from three key data sets: the Office for National Statistics, the React study from Imperial College London, and the Covid symptom tracking app.
None of them are marred by current issues with test and trace data or by people having trouble accessing a test.
The real fallout from the weekend’s statistical chaos is not the numbers, but the people who should have been traced, need to be quarantined and may have instead unintentionally transmitted the virus.
Labor shadow secretary of health Jonathan Ashworth said: “It is shameful and people across the country will understandably be alarmed. ”
He called on Health Secretary Matt Hancock to explain “what happened” and what he plans to do to fix the testing and tracing.
Bridget Phillipson, chief shadow secretary at the Treasury, told BBC Breakfast she wanted to know if this had “had an impact on the government’s decision-making regarding local restrictions”.
PHE data shows Manchester now has the highest infection rate in England, at 495.6 cases per 100,000 people in the week to October 1, down from 223.2 the week before.
Liverpool have the second highest rate, up to 456.4 from 287.1 per 100,000. Knowsley in Merseyside, Newcastle, Nottingham, Leeds and Sheffield have also seen big increases.
From Sept 25 to Oct 2
50 786 Cases initially reported by SPE
15 841 Unreported, missed cases due to computer error
8 days incomplete data
1 980cases per day, on average, were missed during this period
48 hoursIdeal time to find contacts after a positive test
Source: PHE and gov.uk
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