The Impact of Social and Physical Distancing Measures on COVID-19 Activity in England

Background: Mandatory social and physical distancing measures (SPDM) were introduced in the UK on the 23rd March 2020. A multi-tiered surveillance system based on influenza surveillance, was adopted from the early stages of the COVID-19 Epidemic to monitor different stages of disease. We describe how the impact SPDM was detected through each surveillance system and how these systems may be applied to detect increases in COVID-19 activity as SPDM are eased. Methods: Data from national population surveys, web-based indicators, syndromic surveillance, sentinel swabbing, respiratory outbreaks, secondary care admissions, and mortality indicators from the start of the epidemic to Week 20 2020 were used to identify timing of peaks in the indicator relative to the introduction of SPDM. This was compared to median time from symptom onset to different stages of illness or interactions with healthcare services. Results: The impact of SPDM was detected within 1 week through population symptom surveys, web search indicators and through GP sentinel swabbing reported by onset date. There were detectable impacts on syndromic surveillance indicators for difficulty breathing, influenza-like illness and COVID-19 coding at 2, 7 and 12 days respectively. This was followed by hospitalisations and critical care admissions (both 12 days), laboratory positivity (14 days), deaths (17 days) and care home outbreaks (4 weeks). Interpretation: There was a clear impact of SPDM on COVID-19 activity which was detectable within 1 week through community indicators highlighting their importance in early detection of changes in activity. Community swabbing surveillance will be increasingly important as a specific indicator when circulation of seasonal respiratory viruses increases. Funding Statement: There was no specific funding for this report. Declaration of Interests: None declared. Ethics Approval Statement: The surveillance collections included here are approved as Health Protection, under Regulation 3 of The Health Service (Control of Patient Information) Regulations 2002.