Public Health England admitted on Sunday that the agency has under-reported COVID-19 infections by 15,841 cases in recent days due to a "technical issue." The missing positive tests were conducted between September 25 and October 2 and have since been added to national statistics, the agency said.
PHE didn't explain the nature of the technical issue, but a number of British news sources have pointed the finger at Microsoft Excel. Here's how the Guardian describes the issue:
PHE was responsible for collating the test results from public and private labs, and publishing the daily updates on case count and tests performed.
In this case, the Guardian understands, one lab had sent its daily test report to PHE in the form of a CSV file – the simplest possible database format, just a list of values separated by commas. That report was then loaded into Microsoft Excel, and the new tests at the bottom were added to the main database.
But while CSV files can be any size, Microsoft Excel files can only be 1,048,576 rows long. When a CSV file longer than that is opened, the bottom rows get cut off and are no longer displayed. That means that, once the lab had performed more than a million tests, it was only a matter of time before its reports failed to be read by PHE.
The agency says it will take precautions to make sure an error like this doesn't happen in the future.