Information

Coronavirus (COVID-19): state of the epidemic - 13 May 2022

This report brings together the different sources of evidence and data about the Covid epidemic to summarise the current situation, why we are at that place, and what is likely to happen next.

This document is part of a collection


Covid-19 Prevalence

R value, Growth Rate and Estimated New Daily Infections

The reproduction number (R) is the average number of secondary infections produced by a single infected person. If R is greater than one the epidemic is growing, if R is less than one the epidemic is shrinking. The higher R is above one, the more people one infectious person might further infect and so the faster the epidemic grows. Please note that R is an indicator that lags by two or three weeks. For more information please visit the UK government website.

The UK Health Security Agency’s (UKHSA) consensus estimate for R in Scotland as at 26 April is between 0.7 and 0.9. The lower and upper limits of the R value have both decreased since the previous publication (Figure 1)[3] [4].

Figure 1: R in Scotland over time by publishing week [5].
a graph showing the estimated range of R over time as published from May 2021 to May 2022. The estimated lower and upper range moved above 1 in June 2021, September 2021 and January 2022. As at 26 April the estimate for R in Scotland is between 0.7 and 0.9 The chart has a note on 1 April 2022 that says: “change to fortnightly publication schedule”.

As at 26 April, the UKHSA’s consensus view was that the incidence of new daily infections in Scotland was between 16 and 302 per 100,000. This equates to between 900 and 16,500 people becoming infected each day in Scotland[6] [7].

The growth rate reflects how quickly the numbers of infections are changing day by day. It is an approximation of the percentage change in the number of new infections each day. More information can be found on the UK government website.

The latest growth rate for Scotland as at 26 April was between -6% and -3%. The upper growth and lower growth limit have both decreased since the last published figure[8] [9].

Covid-19 Infection Survey – Headline Estimates

The Covid-19 Infection Survey is a UK wide study carried out by the Office for National Statistics (ONS) and the University of Oxford. The survey invites private residential households to test whether they have the infection, regardless of whether they have symptoms, using a PCR test. This means the study is unaffected by testing policy changes. Participants are also asked to provide a blood sample to test for antibodies.

In Scotland, the percentage of people living in private residential households testing positive for Covid-19, as estimated by the Covid-19 Infection Survey, continued to decrease in the most recent week (1 to 7 May), as seen in Figure 2[10]. The estimated percentage of people testing positive in Scotland has been decreasing since the end of March. This follows a peak in the week 14 to 20 March 2022 which saw the highest estimate for Scotland since the survey began. The estimated percentage of people testing positive for Covid-19 in the private residential population in the week 1 to 7 May in Scotland is 3.01% (95% credible interval: 2.57% to 3.45%)[11], equating to around 1 in 35 people (95% credible interval: 1 in 40 to 1 in 30).

In the week 1 to 7 May 2022, estimates for the other nations of the UK are as follows and can be seen in Figure 2:

  • In England, the percentage of people testing positive continued to decrease: 2.21% (95% credible interval: 2.09% to 2.33%), equating to around 1 in 45 people (95% credible interval: 1 in 50 to 1 in 45).
  • In Wales, the percentage of people testing positive continued to decrease: 2.91% (95% credible interval: 2.40% to 3.46%), equating to around 1 in 35 people (95% credible interval: 1 in 40 to 1 in 30).
  • In Northern Ireland, the percentage of people testing positive continued to decrease: 1.84% (95% credible interval: 1.34% to 2.39%), equating to around 1 in 55 people (95% credible interval: 1 in 75 to 1 in 40).
Figure 2: Modelled daily estimates of the percentage of the private residential population testing positive for Covid-19 in the four UK nations, between 27 March and 7 May 2022, including 95% credible intervals [12].
a line chart showing the modelled daily estimates of the percentage of the private residential population testing positive for Covid-19 in each of the four nations of the UK, between 27 March and 7 May 2022, including 95% credible intervals. In the most recent week, the estimated percentage of people testing positive continued to decrease in Scotland, England, Wales and Northern Ireland.

In Scotland, the estimated percentage of people testing positive has decreased for all age groups in recent weeks[13].

Covid-19 Infection Survey – Regional Analysis

The ONS have created sub-regions across the UK for the purposes of providing Covid-19 positivity estimates for the residential populations on a lower level than the four nations. In Scotland, these sub-regions are comprised of Health Boards (for an overview on how these align with local authorities, please see Table 1 in the Technical Annex).

Sub-regional estimates are based on a different model to the headline estimates, and should not be compared to headline positivity estimates. The sub-regional figures may differ from the headline estimates because they are averaged over a longer time period.

There is a higher degree of uncertainty in the sub-regional estimates because of a smaller sample size in each sub-region relative to their respective national sample. This is indicated by wider credible intervals and therefore results should be interpreted with caution.

In the most recent week (1 to 7 May 2022), estimates for the percentage of people testing positive for Covid-19 were similar for all CIS Regions in Scotland and ranged from 3.17% in CIS Region 128 (NHS Ayrshire & Arran, NHS Borders and NHS Dumfries & Galloway) (95% credible interval: 2.65% to 3.81%) to 3.25% in CIS Region 127 (NHS Lanarkshire) (95% credible interval: 2.65% to 3.89%). Overlapping credible intervals indicate that there may not be a true difference between the estimates (Figure 3)[14] [15]. Figure 3 is also available as a dynamic map.

Figure 3: Modelled estimates of the percentage of the private residential population within each CIS sub-region who would have tested positive for COVID-19 in the week 1 May to 7 May 2022 [16].
A colour coded map of the UK shows the modelled estimates of the private residential population within each CIS sub-region who would have tested positive for COVID-19 in the week 1 May to 7 May 2022. The map ranges from light blue for 1.50% to 1.99%, blue for 2.00%-2.49%, darker blue for 2.50% to 2.99%, and very dark blue for 3.00% estimated positivity and over. Scotland CIS sub-regions are marked with very dark blue (3.00% and over positivity).

Covid-19 Wastewater Estimates

The Scottish Government has been working with the Scottish Environment Protection Agency (SEPA) to detect and analyse fragments of Covid-19 virus RNA in wastewater. The levels of SARS-CoV-2 in wastewater are monitored at 141 sites around Scotland. In contrast to Covid-19 case records, virus shedding into wastewater is a biological process. This means that wastewater data is unaffected by factors that impact whether testing is done.

Nationwide, wastewater Covid-19 levels declined slightly in the last two weeks. The week ending 10 May saw levels of around 84 million gene copies per person per day (Mgc/p/d), a decrease compared to 97 Mgc/p/d two weeks ago (week ending 26 April) and 76 Mgc/p/d observed in the previous week (week ending 3 May) (Figure 4)[17].

Although overall there are decreases in wastewater Covid-19 levels across most of Scotland in the last two weeks, 14 local authorities have increased their levels over the past week. Increases were reported in Angus, City of Edinburgh, Clackmannanshire, Dundee City, East Dunbartonshire, East Lothian, Falkirk, Highland, Inverclyde, Midlothian, Moray, Perth and Kinross, Renfrewshire, and West Lothian. Please note that comparisons for Argyll and Bute, Na h-Eileanan Siar, Orkney, Shetland and Stirling are not possible due to sampling coverage.

Figure 4: National running average trends in wastewater Covid-19 from 31 December 2021 to 10 May 2022, and CIS positivity estimates from 31 December to 1 May 2022 [18] [19] [20].
a line chart showing the national running average trends in wastewater Covid-19 from the end of December 2021 to 10 May 2022, and CIS positivity estimates from the end of December 2021 to 1 May 2022. After a steep decrease in early January, Covid-19 wastewater levels appear to fluctuate throughout January and February, with a peak in late March and decreasing levels from early April, albeit with a slight increase seen over the most recent week.

Reported Covid-19 Cases

The LFD Universal Offer for asymptomatic testing came to an end on 18 April 2022. In addition, on 1 May 2022 the purpose of COVID-19 testing shifted from population-wide testing to reduce transmission, to targeted testing and surveillance. Reported cases will no longer be representative of all COVID-19 cases in Scotland, and caution is advised when comparing trends in cases over time. For more information, see the Scottish Government Covid-19 Test and Protect Transition Plan.

Please note that due to testing policy changes, reported cases will no longer be representative of all COVID-19 cases in Scotland, and caution is advised when comparing trends in cases over time. By specimen date, there were 158 weekly combined PCR and LFD cases (including reinfections) per 100,000 population in the week to 6 May (Figure 5)[21]. This follows a period of sharply decreasing case rates since the most recent peak in March. The regular analyses on case rates in different age groups and among care home residents are no longer included in this report.

Figure 5: Seven-day combined PCR and LFD case rate (including reinfections) per 100,000 for Scotland by specimen date. Data to 6 May 2022 [22] [23].
a line graph showing the seven-day case rate (including reinfections) by specimen date per 100,000 people in Scotland, using data from March 2020 up to and including May 2022. In this period, weekly case rates have peaked in January 2021, July 2021, September 2021, early January 2022, and mid-March 2022. The chart has notes explaining that before 5 January 2022, the case rate includes only positive laboratory confirmed PCR tests. After 5 January 2022, the case rate includes PCR and LFD confirmed cases. From 1 May 2022, there is a change in Testing Policy meaning the purpose of COVID-19 testing shifted from population-wide testing to reduce transmission, to targeted testing and surveillance.

The proportion of reinfections among the total weekly cases has increased in the most recent week. By specimen date, there was a total number of 1,159 reinfection cases confirmed by either a PCR or LFD test in the week leading up to 6 May. This represents 13.4% of reported cases, and compares to 12.8% in the week leading up to 29 April [24]. However, this number is likely affected by testing changes and this figure may no longer be comparable over time. The proportion of reinfections have increased rapidly since December 2021 and the emergence of the Omicron variant.

While the LFD Universal Offer for asymptomatic testing came to an end on 18 April 2022 in Scotland, 129,983 LFD tests were reported in the week to 8 May. This is a 29% decrease from the week previously (week to 1 May), when 182,972 LFD tests were reported. This compared to a peak of 865,561 tests being reported in the week to 26 December 2021, while the LFD Universal Offer was still in place[25].

The Scottish Contact Survey[26] continues to ask whether people use LFD tests and if so how often. Approximately 51% of individuals had taken at least one lateral flow test within the last 7 days for the survey pertaining to the period 28 April to 4 May, decreasing from 68% two weeks prior[27].

Antimicrobial Resistance and Healthcare Associated Infection Scotland (ARHAI Scotland) provide analyses on hospital onset acquired Covid-19 infections, where patients are likely to have been infected after being admitted to hospital, based on the date when the sample was collected for a first positive Covid-19 test. Cases where the sample was collected before a hospital admission are considered community onset cases, while samples collected on day eight or later are considered nosocomial cases, or cases likely to have been acquired in a hospital setting. For more information, see this ARHAI weekly publication.

According to data from ARHAI Scotland, 97.8% of the 30,262 Covid-19 cases reported in the week ending 17 April 2022 were reported as community onset cases. 237 cases in the same period were reported as nosocomial cases[28]. This is a 27% decrease from the previous week ending 10 April (324 nosocomial cases). This follows a period of increasing numbers of nosocomial cases since the beginning of February (following a peak in late December 2021 and early January 2022). The number of cases in all categories of inpatient diagnosed COVID-19 cases increased during the same time period, including those diagnosed on day one or two, reflecting the high levels of transmission in the community[29].

In line with recent changes to testing policy and transitions to long term strategies in the four UK nations, cases comparison between countries will no longer be included in the report. For more information see following links for England, Scotland, Wales, and Northern Ireland.

To compare trends in estimated infection levels in private residential households across the UK, please see the previous section on the Covid-19 Infection Survey.

Contact

Email: sgcentralanalysisdivision@gov.scot

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