The statistical quirk that means the coronavirus pandemic may never officially end

The anomaly also means that even if there was no virus in the community at all, we would never fall below 310 cases a day if we were testing at current levels.

Prof Carl Henegehan, director of evidence-based medicine, Oxford University, said: “It does matter when your prevalence is very low. At this point if you have a positive test you are more likely not to be infected than to actually have the virus. Your chance of being infected is less than 30 per cent. 

“The ONS currently cannot estimate prevalence because it does not now know what the false positive rate of PCR testing is. 

“It looks like we’ll struggle to get out of this. We’re now in a spiral of bad data.”

Testing is currently picking up around 1,000 tests per day, perhaps because it is targeting hotspots, rather than the country as a whole. Yet the analysis suggests hundreds of those could be false positives. 

The problem is so bad that the ONS admitted in a recent analysis of its surveillance statistics that all its positive cases could be false between April 26 and June 28.

“Even in a purely hypothetical situation that the virus is not circulating, a test specificity of 99.9 per cent would be associated with an expected number of positive tests that is approximately equal to what we observed over the entire study period,” the ONS said. 

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