COVID-19: Record number of daily cases detected in UK - but could the real number be thousands higher?

·2-min read

More than 100,000 COVID-19 cases have been detected in the UK on a single day – a record since the pandemic began.

Although 106,122 cases were reported in the latest 24-hour period, data from the UK Health Security Agency shows 103,281 cases were identified on 15 December alone.

Cases identified have always remained a fraction of the actual infection rate in the real world. One estimate from the Scientific Advisory Group for Emergencies (SAGE), a group of scientists advising the government, suggests "hundreds of thousands of new Omicron infections per day".

This means thousands of asymptomatic cases are likely going undetected.

One indicator of how many infections are being detected is the positivity rate, which has risen to 14.8% in England - the highest level since mid-January.

Positivity is the percentage of people who test positive for the virus of those who have been tested.

A higher positivity suggests higher transmission and that there are likely more people with coronavirus in the community who haven't been tested yet, according to Johns Hopkins University.

Testing has been ramped up across the country to keep up with the rise in infections. More than three million people have been tested every week since early December in England - higher than at any point in the pandemic.

But the new variant's high growth rate - doubling every two days - has meant that even the record number of tests might be stretching the limits of the government's testing capacity.

Data shows that laboratories can test more than 250,000 additional samples every day despite processing half a million PCR tests each day over the past week.

But capacity allocated at the community level is likely to be much smaller as a large portion is reserved for testing patients and healthcare workers in hospitals.

Data also shows that the infection rate and testing capacity vary across the nation.

One in five tests in London returns positive, indicating a higher positivity rate than the England average.

Scientists suggest that due to the doubling time of Omicron, increasing the number of tests to keep up with a rise in infections will be difficult.

Kevin McConway, emeritus professor of applied statistics at the Open University, said demand for PCR tests is likely to outstrip supply within a week if cases continue to increase at the current rate.

Regardless of whether infections rise or fall in the coming weeks, scientists say that tracking COVID-19 is likely to be difficult due to the "unpredictable changes in behaviour around the festive period" during a crucial time for the pandemic.

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