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Latest REACT-1 data show rapid growth in COVID-19

As the number of infections of COVID-19 rise across the UK in the so-called ‘second wave’, the latest data from the Real-time Assessment of Community Transmission-1 (REACT-1), which was established to specifically track the course of infection, quantifies the extent of the spread of the virus and provides some alarming estimates.

REACT-1 was established in May 2020 by a team from Imperial college, London and involves obtaining nose and throat swabs from non-overlapping random samples of the population of England, at ages 5 years and above, obtained from a list of GP registered patients as the sampling frame. The swabs are sent to patient’s homes and collected via courier and PCR tested. To date there have been five rounds of data collection and the team use this data to analyse trends in swab positivity and provide weighted and unweighted population estimates. The latest publication includes data from round 6, collected from 16 to 25 October 2020 and is therefore as current as possible.

In the latest round there were 863 positive swabs from a total of 85,971, giving an unweighted prevalence of 1% and a weighted prevalence of 1.28% (95% CI 1.15–1.41%). Compared with round 5 (18 September to 5 October 2020) where the weighted prevalence of was 0.60%, the latest figures suggest that the prevalence of COVID-19 has more than doubled. Putting the REACT-1 data into perspective, the authors estimate that around 960,000 individuals have the virus on any one day and that this will lead to approximately 96,000 new infections per day. Interestingly, this latest weighted prevalence is the highest recorded compared to earlier rounds. For instance, the paper reports that in round 1 (1 May to 1 April 2020), the weighted prevalence was 0.16%. Additionally, the latest figures indicate that the prevalence was highest in Yorkshire and the Humber at 2.72% and lowest in the East of England at 0.55%. Epidemic growth is no longer fastest in the North of England but is increasing in the South East, East of England, London and the South West. Furthermore, prevalence has increased across all age groups with the greatest increase now among those aged 55–64, up threefold from round 5 although the highest weighted prevalence remains in the 18–24-year-olds at 2.25% an increase from 1.59% in round 5.

This increased prevalence gave an average R number of the period of rounds 5 and 6 of 1.20. The authors note that their most recent data suggests a national doubling of infection rates every 9 days and that this corresponds to an R value of 1.56.

They conclude by stating that the epidemic has now reached a critical stage and that it is time to introduce more stringent measures to control the virus and thus avoid more hospital admissions and deaths.

Riley S et al. High prevalence of SARS-CoV-2 positivity and increasing R number in England during October 2020: REACT-1 round 6 interim report. MedRxiv 2020.

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