SARS-CoV-2 prevalence in England “Higher than at any time from May 2020.”

The UK, and England in particular, was badly hit by the COVID-19 pandemic, with the numbers of patients requiring hospitalization and/or intensive care unit (ICU) admission and mortality zoomed during the first wave of the infection.

SARS-CoV-2 Virus

Image Credit: Andrii Vodolazhskyi/Shutterstock.com

A recent study reports the findings of the REal-time Assessment of Community Transmission-1 (REACT-1) study in terms of community prevalence.

Rising Prevalence

The REACT-1 study began in May 2020, at the end of the lockdown phase, and longitudinal surveys were administered to track the trends. The researchers found a steep decline in the number of cases in May, lasting until the beginning of August 2020. In the middle of the latter month, the case number began to rise again with the reproduction number (R) value at 1.7. The latest data collection round took place from September 18 to September 26, 2020.

The current report describes recent trends and prevalence when compared with earlier results from the last four rounds. In these nine days, there were over 84,800 swabs of which 363 swabs were positive, for a prevalence of 0.55%, indicating that the prevalence continues to rise. This is the highest point in the study so far and is more than four times as high as that observed in the previous round.

The researchers estimated a doubling time of 10.6 days in the period between 20th August to 26th September 2020, with a reproduction number R of 1.47. But if only the last round of data is used, the slope is seen to become gentler as R slowly drops to 1.06.

Greatest Prevalence Among Young Adults

While the prevalence increased across all ages and all regions, the highest prevalence was in the group aged 18-24 years, at almost 1%. With high infection rates among young adults, transmission in colleges is very likely to shoot up, and in fact, local clusters of infection amounting to outbreaks are already being seen on such campuses.

Highest Rate of Increase Among Elderly

However, the relative increase in prevalence was greatest in those above 65%, from 0.04% to 0.29%, from the last round to the current one, indicating a more than seven-fold increase. This group is at the highest risk for severe disease and death related to COVID-19, and an increase in prevalence in this subset will push up the number of hospitalizations and mortality.

Variations by Race and Region

Asian and Black individuals were at a two-fold higher risk of infection than white participants. Across regions, the highest prevalence was in the North West at 0.86%, and there was a fivefold increase in London from 0.10% to 0.49%. R was found to be between 1.32 to 1.63 in various regions of England. Many widely scattered clusters were found in the Northwest, Midlands, and the region in and around London. New clusters were seen in the South West, North East and East of England.

Over 400,000 Swab-Positives on Any Day

The study reports that swab positivity has now gone up to more than 1 in 200 over the whole population in England.

From a low point in the period between May and September 2020, the prevalence has gone up such that there are now, on the estimate of researchers, about 410,000 people in England who test positive for the virus on any day if just three-quarters of positive nasal and throat swabs taken at home are correctly detected.

Slowing Rate of Increase in Prevalence

However, the rising rate of prevalence seems to have slowed at present. The reduction in the rate of increase of prevalence follows stronger campaigning by the government for the population to follow strict social distancing, in all kinds of social interactions, including pub curfews at the early hour of 10 pm, and the implementation of local lockdowns in quick succession in areas and groups at high transmission risk.

Such measures not only produce physical protection from viral spread but can enhance the public awareness of the scale of the epidemic in England, which will help to reinforce and continue public cooperation with containment measures.

Implications

The REACT-1 study is different from those in which symptomatic individuals are tested, and is independent of testing capacity, being based on a random sampling of the population at large. This enables the investigators to provide “reliable and timely data on trends in the prevalence of SARS-CoV-2.”

To prevent outbreaks, increased public health efforts must build trust and cooperation with social distancing, hand hygiene, face mask use, and related measures, at the national level and not just within affected communities. This shift is being implemented by the government at present.

A second implication is that the current epidemic in England is no longer arising in hospitals and care homes but within the community. Minorities like Blacks and Asians are still being disproportionately affected.

The most recent data shows a higher percentage of symptomatic people compared to the previous rounds. The availability of testing may have played a role in the apparent increase in prevalence, but it is also likely that this is due to a higher viral load and therefore of symptomatic infection among individuals in the population. This is suggested, moreover, by a higher cycle threshold in the recent data. Rates of increase in prevalence are comparable among symptomatic and asymptomatic groups.

The researchers point out that since the middle of August, there “has been a resurgence of the virus in the community, with rates higher now than at any time since we started measuring prevalence in May 2020.” This signals the necessity of stepping up efforts to stem community transmission, to limit the number of hospitalizations and deaths from this disease.

*Important Notice

medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.

Journal reference:
  • Riley, S. et al. (2020). High Prevalence Of SARS-Cov-2 Swab Positivity in England During September 2020: Interim Report of Round 5 Of REACT-1 Study. medRxiv preprint. doi: https://doi.org/10.1101/2020.09.30.20204727. https://www.medrxiv.org/content/10.1101/2020.09.30.20204727v1
Dr. Liji Thomas

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Dr. Liji Thomas

Dr. Liji Thomas is an OB-GYN, who graduated from the Government Medical College, University of Calicut, Kerala, in 2001. Liji practiced as a full-time consultant in obstetrics/gynecology in a private hospital for a few years following her graduation. She has counseled hundreds of patients facing issues from pregnancy-related problems and infertility, and has been in charge of over 2,000 deliveries, striving always to achieve a normal delivery rather than operative.

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