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.
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].
| 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% |
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