Coronavirus (COVID-19): modelling the epidemic (Issue No.100)

Latest findings in modelling the COVID-19 epidemic in Scotland, both in terms of the spread of the disease through the population (epidemiological modelling) and of the demands it will place on the system, for example in terms of health care requirement.

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Technical Annex

Epidemiology is the study of how diseases spread within populations. One way we do this is using our best understanding of the way the infection is passed on and how it affects people who catch it to create mathematical simulations. Because people who catch Covid-19 have a relatively long period in which they can pass it on to others before they begin to have symptoms, and the majority of people infected with the virus will experience mild symptoms, this "epidemiological modelling" provides insights into the epidemic that cannot easily be measured through testing e.g. of those with symptoms, as it estimates the total number of new daily infections and infectious people, including those who are asymptomatic or have mild symptoms.

Modelling also allows us to make short-term forecasts of what may happen with a degree of uncertainty. These can be used in health care and other planning. The modelling in this research findings is undertaken using different types of data which going forward aims to both model the progress of the epidemic in Scotland and provide early indications of where any changes are taking place.

The delivery of the vaccination programme will offer protection against severe disease and death. The modelling includes assumptions about compliance with restrictions and vaccine take-up. Work is still ongoing to understand how many vaccinated people might still spread the virus if infected. As Covid-19 is a new disease there remain uncertainties associated with vaccine effectiveness. Furthermore, there is a risk that new variants emerge for which immunisation is less effective.

What levels of Covid-19 are indicated by wastewater data?

Table 1 provides population weighted daily averages for normalised WW Covid-19 levels in the weeks ending 17th May and 24th May 2022, with no estimate for error. This is given in Million gene copies per person per day. Coverage is given as percentage of inhabitants in each local authority covered by a wastewater Covid‑19 sampling site delivering data during this period[11].

Table 1. Average Covid-19 wastewater levels (Mgc/p/d) [12].
Local Authority (LA) w/e 17th May w/e 24th May Coverage
Aberdeen City 67 83 99%
Aberdeenshire 77 65 52%
Angus 50 66 68%
Argyll and Bute 65 85 12%
City of Edinburgh 79 79 96%
Clackmannanshire 51 98 92%
Dumfries and Galloway 49 51 39%
Dundee City 64 56 100%
East Ayrshire 94 72 72%
East Dunbartonshire 168 80 99%
East Lothian 70 79 56%
East Renfrewshire 56 62 95%
Falkirk 98 62 96%
Fife 45 72 84%
Glasgow City 97 71 75%
Highland 81 76 48%
Inverclyde 54 23 98%
Midlothian 77 85 88%
Moray 83 99 70%
Na h-Eileanan Siar 23 21%
North Ayrshire 69 50 92%
North Lanarkshire 64 79 95%
Orkney Islands 41 0%
Perth and Kinross 53 60 45%
Renfrewshire 70 45 97%
Scottish Borders 44 92 48%
Shetland Islands 38 27 29%
South Ayrshire 93 70 88%
South Lanarkshire 75 90 88%
Stirling 13 35 63%
West Dunbartonshire 86 45 98%
West Lothian 53 83 85%

Contact

Email: sgcentralanalysisdivision@gov.scot

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