One Covid-19 cluster responsible for majority of transmission among Cambridge students last term, study finds

Louis Mian 13 January 2021
Image Credits: Wikimedia Commons

Using data from the University’s asymptomatic screening programme, an interim report issued by the Covid-19 Genomics UK Consortium has found that one cluster of Covid-19 was responsible for the majority of transmission among Cambridge students beyond the third week of last term. This cluster grew from 30 to 139 cases between the second and fifth weeks.

In total this cluster involved students from 101 households, 41 courses, and 29 colleges and the report states that ‘the earliest available genomes’ of this cluster are from 15 students, six studying the same course.

The study outlines that ‘after placing this cluster in the national and international context, we have identified the likely source region’, but does not state the region in question.

Two other clusters of the virus, involving 32 and 22 infections, are highlighted in the report, but these were largely contained within particular colleges. No ‘further growth of either cluster is seen after week 3 indicating likely cessation of transmission’, demonstrative of the success of measures to control the spread of the virus.

From this data, the report emphasises ‘the importance of outbreak containment’, as ‘early outbreaks appear to have halted when confined within Colleges’.

The report further details that there is little evidence of cross-transmission between students and other Cambridge residents in the first five weeks of Michaelmas term. It outlines that this ‘may reflect the efficacy of a structured University wide screening programme’.

There was also a notable lack of diversity in lineages of the virus in the first few weeks, suggesting that only a ‘few introductions led to established outbreaks of SARS-CoV-2 in the University population’.

Dr Dinesh Aggarwal, a member of the Consortium and a researcher at the University’s Department of Medicine, has explained that ‘it appears that a few instances of the virus being introduced to the University account for the majority of cases of established transmission.’

‘This suggests to us that in most cases, when a virus was introduced, students behaving responsibly and complying with infection control measures helped stop the virus in its tracks.’

‘We hope it will be particularly reassuring that so far we have not found evidence of substantial transmission between our students and the local community,’ Aggarwal continued.

One of the academics behind the university’s asymptomatic screening programme, Dr Ben Warne, also emphasised that these findings demonstrate how ‘widely-distributed outbreaks are more challenging to control, potentially resulting in continual spread.’

‘Genomics should help us piece together this puzzle and help us target prevention strategies.’

Meanwhile, Head of the University’s School of Clinical Medicine, Professor Patrick Maxwell, announced that this report demonstrates the asymptomatic screening process ‘has paid off’.

‘Asymptomatic screening can help identify cases of infection early, including where students are unaware of infection, and inform infection control measures. This has never been more urgent, with the emergence of the new variant,’ Maxwell stated.

Read more: Asymptomatic screening and genome sequencing help Cambridge understand spread of SARS-CoV-2 among its students | University of Cambridge