Last modified on Tue 1 Jun 2021 12.34 EDT Nearly three-quarters of coronavirus cases among University of Cambridge students last autumn have been traced back to a single nightclub, highlighting the risks of reopening venues in the next phase of the UK government’s roadmap. Students who attended socially distanced events during freshers’ week and over Halloween were the source of the biggest infection cluster at the university, according to researchers who analysed the effectiveness of Cambridge’s coronavirus screening programme, which tested 10,000 students weekly at its peak and was the largest in the UK. Genomic sequencing showed that the virus spread rapidly among students who mixed between households and courses on nights out. Cases fell dramatically once the second lockdown was announced, as students complied with the rules and socialised within households of six to 20. Further outbreaks were curtailed by the expansion of a PCR testing programme, which the university estimates reduced the rate of transmission by a third.