Why there is more Omicron than we know

Yesterday the UK Health Security Agency (UKHSA) announced it had identified another 26 Omicron cases, and the total number of cases in the UK had reached 160.

The rate of increase from zero in little over a week seems significant. But the one thing we know is these official figures are a significant underestimate of how many cases are actually in the UK.

Here’s why.

First, you will recall that last week I reported UKHSA’s statement to me that only 50 per cent of pillar 2 or community testing can assess Covid-19 samples for s-gene target failure – which means only half of the labs pick up that initial clue (not proof) that any given positive result is Omicron rather than Delta.

So for the other half of labs, there is no way yet of screening positive results to determine whether they should be sent on for the gene sequencing that establishes whether any particular infection is indeed Omicron, or a different strain (UKHSA told me they were taking steps to address this shortcoming).