Nature reports:

Scientists are scratching their heads over the precipitous decline in daily COVID-19 infections in the United Kingdom following their rapid rise earlier in the year. Officially recorded new cases more than halved in just two weeks: from a high of 54,674 on 17 July to 22,287 on 2 August.

“Nobody really knows what’s going on,” says epidemiologist John Edmunds at the London School of Hygiene and Tropical Medicine (LSHTM). In particular, it’s not clear whether this sudden trend indicates that the peak of the third wave has passed, or whether it is a blip caused by complex social factors.

The spread of the more-infectious Delta variant of SARS-CoV-2 in the United Kingdom seemed, despite the country’s successful vaccination roll-out, to be creating a dangerous crisis. Exponential growth in infections since June led to predictions of as many as 100,000 new cases being reported daily, and fears that the National Health Service (NHS) could be overwhelmed by hospitalizations. In such a climate, many scientists felt that the government’s full relaxation of mitigating restrictions in England, such as mask wearing and the closure of nightclubs and other venues, on 19 July was reckless.

It is still too early to know what effect the relaxation will have, given that the data on new cases and hospitalizations have a lag of around two weeks. Few public-health experts, however, anticipated the recent sharp drop — and they are struggling to interpret it. [Continue reading…]