A striking observation was that following the first lockdown, the majority of virus lineages that had been circulating in the population in Scotland appeared to become extinguished. Very few lineages persisted over the summer. This supports the idea that it is possible to eradicate the virus from a country when stringent public health measures are in place. What was then observed going into the second wave is that disease was caused by new lineages that has been introduced into the country, many of which could be traced to introductions from countries outside of the UK. Summer holidays and other travel abroad taken at a time when disease was under control in Scotland, but less so elsewhere, has had a predictable outcome.
In Wales, the analysis identified that the current population of circulating SARS-CoV-2 is also different to the lineages that were present in March and April 2020. Early on in the pandemic, a high proportion of cases could be linked to imports into Wales, with a drop in both the number of extant lineages and new introductions following the first lockdown. Like Scotland, Wales observed that the majority of lineages circulating in Wales appeared to become extinguished following the package of measures introduced in Wales as part of the first lockdown.
Wales also observed that after the easing of the first lockdown, the rise in cases forming the start of the second wave was driven by imports — from other parts of the UK and the wider world. The Welsh analysis also examined transmission on a more local level, identifying that cases in areas of high population density (cities) were more likely to result from local chains of transmission, whereas those in less urban areas were more likely to be associated with imports from elsewhere and rarely led to local onward transmission.
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