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Caused by the highly contagious pathogen, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the dreaded but expected second wave of coronavirus 2019 (COVID-19) has already hit the UK. This can be seen in the current high prevalence of infections across the country. Therefore, the virus is set to take a heavy toll on the country’s public health and ultimately many of its citizens’ lives unless timely containment measures are put in place, says a recent study published on the prepress server. medRxiv. *
Study: High prevalence of SARS-CoV-2 swab positivity and increased R number in England in October 2020: REACT-1 round 6 interim report. Image credit: Tanya Panova / Shutterstock
The first wave of pandemic in the UK occurred between March and April 2020, characterized by a high peak of infection and then a sharp and continuous decline in new infections that lasted until early August. From this point on, there was a steady increase in infections, with the reproduction number (R) remaining above 1, indicating a spreading epidemic.
Increasing prevalence
This paper reports the preliminary results of the sixth round of the REal-time Assessment of Community Transmission-1 (REACT-1) study, which has charted the path of the epidemic in England since May this year (2020). The results of the fifth round, based on examination of the viral RNA test by reverse transcriptase-polymerase chain reaction (rt-PCR) from 18 September to 5 October, showed that the national prevalence was again at elevated levels; 0.60%, with a high concentration of cases in the northern parts of the UK.
The sixth round of testing occurred between October 16 and October 25. This included approximately 86,000 swabs, of which approximately 860 were positive, for a crude prevalence of 1%. However, the weighted prevalence is 1.28%, which indicates that the prevalence has more than doubled within 20 days.
Prevalence of swb positivity from lower tier local authorities for England for round 5 (left) and round 6 (right). Regions: NE = North East, NW = North West, YH = Yorkshire and the Humber, EM = East Midlands, WM = West Midlands, EE = East of England, L = London, SE = South East, SW = South -west.
Ascending reproduction number
This increase in prevalence also produced a reproduction number of 1.20 for rounds 5 and 6. Although this is similar to the 1.16 reported in round 5, the isolated results from round 6 indicate that the reproduction rate has increased. lately. In fact, the doubling time for the UK in round 6 is now 9 days, which suggests an R value of 1.56.
These results indicate a higher prevalence and R-value, if the number of double positive genes in both rounds is used, or if the Ct value is used for the N gene, as well as for asymptomatic individuals. Overall, however, prevalence has increased in all regions since the last cycle.
Weighted prevalence is highest, at 2.72%, in the north of England; namely, in Yorkshire and The Humber, while in the North West, it stands at 2.27%. Here, however, the highest growth rate appears to have shifted from 18 to 24 to seniors and school children.
The lowest weighted prevalence is found in south east England, at 0.55%. However, these figures may be misleading as the epidemic growth is now higher, with the R-value exceeding 2 in the south-east and east of England, London and the south-west. The highest growth rate in the Southwest is still among those between the ages of 18 and 24.
Rapid viral spread
Researchers say the R-value is 99% likely to be greater than 1, indicating a spreading epidemic in most regions of the second group, while in the Southwest and West Midlands the probability is slightly lower, perhaps between 95% and 99%.
High-risk groups infected
Although all age groups had a higher prevalence in this round, the largest increase was recorded in the 55-64 age group, at 1.20%, which denotes a three-fold increase over to the prevalence of the previous round of 0.37%. The prevalence was doubled to 0.81% in the age group 65 and over. However, the highest prevalence continued to be in the 18-24 age group at 2.25%, compared with 1.59% in the last cycle.
The unemployed are 0.64% less likely to get the infection than those who come into contact with others in the course of their work. Those who lived in richer areas were also less likely to get infected, judging by the positivity of the swab. Therefore, both age and socioeconomic deprivation appear to be the factors that mainly influenced the probabilities of positive swab.
In the last two rounds, the infection clusters appear to be predominantly in Lancashire, Manchester, Liverpool and West Yorkshire.
The researchers say these October 2020 results represent an acceleration of the second wave of infections in England. This is evidenced by the increase in the R-value of 1.6, compared to 1.2 previously, while more infections occur in older high-risk individuals over 65, rather than just in the low-risk age group from 18 at 24 years old.
Furthermore, prevalence, which was highest in northern England, is now showing signs of declining. Nonetheless, the significant increases in prevalence still observable among individuals aged 65 and over. In fact, the highest growth rate is now recorded in the Midlands and the South of England, which mirrors the age range and growth patterns previously observed in Northern England during rounds 4 and 5.
Current interventions are not enough
The government has implemented several non-pharmaceutical interventions (NPIs) to reduce the rate of viral spread during the required social and economic interactions. These interventions include free testing (with mandatory isolation and quarantine of infected people and their families), contact tracing and quarantine, and contact tracing (or possible exposures) in the event of an infection cluster. Social gatherings are also limited in size by law, and masks must be worn in shops and on public transport.
Some regions have stricter restrictions on the type of economic activity allowed, with hotels, restaurants and bars bearing the brunt. Those who work in these services are exposed to the majority of external visitors who are themselves at increased risk of contracting infections.
The problem, the researchers point out, is that the policies themselves, individually or in combination, coupled with the planned easing of risk-level restrictions and current compliance rates, are not enough to reduce the R-value below 1, which it means that the epidemic will continue to spread.
In fact, they estimate that on average there are around 1 million infected individuals in England on any given day with current prevalence, assuming that nasal and oral swabs have a sensitivity of 75% to the virus and that viral detection is possible up to 10 days from infection.
Previous cycles of data have shown that half or more of patients with positive viral tests have no symptoms at the time of the test or during the previous week. This indicates that if only symptomatic cases are counted, the population incidence will be falsely low.
Implications
All individuals with symptoms may not have chosen to participate in the current survey, but this may not have significantly affected the results. Second, the researchers used self-taken swabs that may have produced false negatives in 20-30% of the participants. However, this should not affect the trends as this has been the practice in all cycles up to the current one and as the laboratory procedures used in all cycles have been identical.
The researchers then conclude: ‘The second wave of the epidemic in England has now reached a critical stage.’ The inevitable result of the accelerated transmission will be heavy hospitalizations and a high mortality rate. To avoid this, they urge: “Whether through regional or national measures, it is now vital to control the virus and bring R under one.”
*Important Notice
medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be considered conclusive, guide clinical practice / health-related behavior, or treated as consolidated information.
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