Public Health England said its investigation into a technical issue with the Government’s coronavirus dashboard identified more than 15,000 cases which were not included in the daily reports between September 25 and October 2.
For example, 4,786 cases which were due to be reported on October 2 were not included in the daily total on the dashboard that day, when the figure was given as 6,968.
Michael Brodie, the interim chief executive at Public Health England, said: “A technical issue was identified overnight on Friday 2 October in the data load process that transfers Covid-19 positive lab results into reporting dashboards.
“After rapid investigation, we have identified that 15,841 cases between 25 September and 2 October were not included in the reported daily Covid-19 cases. The majority of these cases occurred in most recent days.
“Every one of these cases received their Covid-19 test result as normal and all those who tested positive were advised to self-isolate.
“NHS Test and Trace and PHE have worked to quickly resolve the issue and transferred all outstanding cases immediately into the NHS Test and Trace contact tracing system and I would like to thank contact tracing and health protection colleagues for their additional efforts over the weekend.
“We fully understand the concern this may cause and further robust measures have been put in place as a result.”
Test and Trace and Public Health England joint medical adviser, Susan Hopkins, said the issue had not prevented people receiving their test result or affected decision-making in local areas.
She said: “Our analysis now shows that this issue affected a total of 15,841 cases from the period between 25 September and 2 October, with the majority occurring in recent days. This means the total number of positive cases over this period was higher than previously reported.
“Of these, over 75% (11,968) relate to cases that should have been reported between 30 September and 2 October.
“This issue did not affect people receiving their Covid-19 test results and all people who tested positive have received their Covid-19 test result in the normal way. It also does not impact the basis on which decisions about local action were taken last week.
“All outstanding cases were immediately transferred to the contact tracing system by 1am on 3 October and a thorough public health risk assessment was undertaken to ensure outstanding cases were prioritised for contact tracing effectively.
“The advice remains the same. If you have tested positive you must self-isolate immediately for at least 10 days from when your symptoms began and we urge everyone who is contacted by NHS Test and Trace to provide details of their recent contacts.”
The Government’s dashboard said that, as of 9am on Sunday, there had been a further 22,961 lab-confirmed cases of coronavirus in the UK. It brings the total number of cases in the UK to 502,978.
The daily figure includes 15,841 additional cases which were recorded between September 25 and October 2 but not included on previous days because of a technical issue, the dashboard said, adding Sunday’s data is “therefore artificially high for England and the UK”.
The Government also said a further 33 people had died within 28 days of testing positive for Covid-19 as of Sunday. This brings the UK total to 42,350.
Separate figures published by the UK’s statistics agencies show there have now been nearly 57,900 deaths registered in the UK where Covid-19 was mentioned on the death certificate.