In the UK the number of cases rose rapidly.
But the public – and authorities – are only learning this now because these cases were only published now as a backlog.

The reason was apparently that the database is managed in Excel and the number of columns had reached the maximum.

Here is the article https://www.dailymail.co.uk/news/article-8805697/Furious-blame-game-16-000-Covid-cases-missed-Excel-glitch.html

Glad that they are apparently now working on a solution. Not one, but several Excel spreadsheets…

It is now also the main headline at the BBC: https://www.bbc.co.uk/news/uk-54412581
At the end of last week confirmed cases were "actually nearer 11,000" – about 4,000 more than reported.

This is very, very bad and also means that the outbreak is much more rapid than thought.

Poorly managed is not just a huge problem in the COVID-19 pandemic – and helping to improve this situation is one of our main motivations to build http://OurWorldInData.org  https://twitter.com/MaxCRoser/status/1313112825385095168

The BBC has now published details on how the Excel screwup happened: https://www.bbc.co.uk/news/uk-54422505