COVID-19 Asymptomatic and Pre Symptomatic transmission rates: FOI release

Information request and response under the Freedom of Information (Scotland) Act 2002

Information requested

1. information about the Scottish Government's position on the transmission rates of COVID-19 by Asymptomatic and Pre Symptomatic persons within Scotland, and what papers/research has the Scottish Government used to reach this position; and
2. reasons why the Scottish Government had not advised (by 06 July 2020) for the public to wear face coverings when visiting museums, galleries and heritage attractions, especially those parts that include enclosed spaces.


I have divided the response in the topics you have raised:

1. Information about the Scottish Government’s Position on Transmission Rates of COVID-19 by Asymptomatic and Pre-symptomatic People, as Papers/Research to Support this Position 

Asymptomatic and pre-symptomatic transmission of COVID-19 can occur, which presents a challenge for suppressing the virus as there is a potential risk for individuals to be mixing with others, whilst not presenting symptoms. The exact risk of transmission compared to symptomatic individuals is, however, not known. Additionally, the Scottish Government does not hold information on the transmission rates of COVID-19 by only asymptomatic and pre-symptomatic people. For this reason, the decision-making process around asymptomatic and pre-symptomatic transmission, as well as any other COVID-19 related issue, has always been and continues to be based on the available scientific and medical evidence from:

  • the World Health Organisation (WHO);
  • the UK Scientific Advisory Group for Emergencies (SAGE) – the latest publically available
  • evidence from SAGE is here; and
  • the Scottish Government COVID-19 Advisory Group, details of which can be found here.

Please note that SAGE and the Scottish Government COVID-19 Advisory Group, as well as other UK advisory groups such as the New and Emerging Respiratory Virus Threats Advisory Group (NERVTAG) and the Scientific Pandemic Influenza Group on Modelling (SPI-M), discuss the emerging evidence of transmission of COVID-19 separately. Each of them also publishes separate papers, which may cover the asymptomatic and pre-symptomatic transmission of the virus.

Under FOISA, we do not hold any research that is not publicly available from any advisory body for the UK Government, such as SAGE, NERVTAG and SPI-M. Therefore, the Scottish Government does not hold detailed information about their assessments. 
However, I believe that you might find the following information useful.

You may be aware that the Scottish Government uses epidemiological modelling to estimate the reproduction rate Rt. That is a measure of the average number of people that would be infected by one individual with COVID-19. If Rt is 2, then two people would be infected by one person on average. If Rt is above 1 then it shows that the virus is spreading in the population, and if it’s below 1 then it’s declining in the population. Therefore, based on the Rt number, the Scottish Government has an estimate of the total number of COVID-19 infections, including those who are asymptomatic or have mild symptoms. You can find more information about the Scottish Government’s epidemiological modelling in this link:

Please note that the understanding of asymptomatic and pre-symptomatic transmission has evolved as scientific evidence has emerged. As a result, the Scottish Government’s actions have and will continue to develop in response to what the scientific community learn about this virus over time. The Scottish Government Covid-19 Advisory Group interprets and applies advice from SAGE and other appropriate sources of evidence and information and uses it to advise Ministers to inform decisions in Scotland.

The attached table has advice on the asymptomatic and pre-symptomatic transmission and the measures taken by the Scottish Government based on this advice (all the minutes from the SAGE meetings cited below can be found here and the ones from the Scottish Government Covid-19 Advisory Group meetings are here):

Lastly, I have noted below links to papers from different advisory groups which consider asymptomatic and pre-symptomatic transmission:

2. Face Coverings in Indoor Settings

The Scottish Government published on 6 July the good practice guidelines for re-opening museums, galleries and heritage attractions during the coronavirus pandemic, with the latest update to the guidance on 30 July. In the time since you have been in touch, the wearing of face coverings is now mandatory in retail, public transport and various other indoor settings. The updated guidance of face coverings (published on 23 September) can be found here. Included in the guidance is a list of settings that are considered to be an indoor public place and where the wearing of a face covering is mandatory. This list includes museums, galleries and indoor tourist, heritage or cultural sites. 

The Scottish Government takes a 4 harms approach to decision making to the pandemic, approach that has been made clear in Scotland’s Strategic Framework. As mentioned above, the Scottish Government considers a wide range of evidence before reaching its conclusions and will continue to make decisions informed by the available scientific and medical evidence. Regarding face coverings, decisions were based on scientific evidence and advice from the World Health Organisation (WHO) and Scientific Advisory Group for Emergencies (SAGE) and the Scottish Government Covid-19 Advisory Group.

The decision to make face coverings mandatory from 7 August 2020 when visiting museums, galleries and heritage attractions, was based on the evidence available at the time.
I have noted below links to the appropriate information :

  • On 4 June 2020, SAGE discussed mitigation measures which included the use of face covering.  You can find further information in the meeting minutes which are available on the UK Government website here.
  • The World Health Organisation released update advice on face covering on the 5 June 2020.  The guidance advised that to prevent Covid-19 transmission effectively in areas of community transmission, governments should encourage the general public to wear face coverings in specific situations and settings as part of a comprehensive approach to suppress Covid-19 transmission. You can find a copy of this guidance on the WHO website here.
  • The UK Government released a summary of the relevant SAGE reports for this topic. This can be found on the UK Parliament website here.

We continue to review our policies regularly in light of the emerging evidence on coronavirus and so we would urge you to continue to use the hyperlinks to find the latest position. 
It is important to note that physical distancing, hand hygiene and respiratory hygiene are the most important and effective things we can all do to prevent the spread of coronavirus. The wearing of face coverings must not be used as an alternative to any of these other precautions.

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