Monitoring influenza-like symptoms in the UK through participatory surveillance: Insights from FluSurvey over two winter seasons (2023-24 and 2024-25)
- 1Immunisation and Vaccine Preventable Diseases Division, UK Health Security Agency, London, United Kingdom
- 2Chief Data Officer Group, UK Health Security Agency, London, United Kingdom
- 3NIHR Health Protection Research Unit in Respiratory Infections, Imperial College London, London, United Kingdom
Abstract
FluSurvey is a participatory surveillance system used to monitor trends in influenza and other respiratory viruses through weekly symptom surveys among the UK population. We aimed to characterise the wider impact of “influenza-like illnesses” (ILI) among FluSurvey participants and assess correlations of ILI with other established influenza surveillance systems. We included data reported by FluSurvey participants over the 2023–24 and 2024–25 winter seasons. Using weekly symptoms surveys, we derived ILI episodes and estimated the proportion reporting healthcare service use, medication use, impact on daily life, absenteeism and use of tests. We applied existing methodologies (omitting first report and weighting to the age-sex structure of England) and assessed cross-correlations of weekly FluSurvey ILI rates with the national surveillance of GP ILI consultations, influenza hospital admissions, and influenza PCR test positivity at time lags of up to +/-2 weeks. There were 3057 participants over two winter seasons (N2023-24 = 2540, 63% female, mean age 60 years; N2024-25 = 2273, 64% female, mean age 61 years). Of 1868 ILI episodes, only a minority contacted healthcare services (14%, most frequently visiting the GP). A large proportion of episodes reported medication use (89%), impact on daily life (75%) and missing school or work (47%). Testing frequency notably declined in the 2024–25 season compared to 2023–24. FluSurvey ILI rates were strongly correlated with other influenza surveillance, predominantly leading GP ILI consultations (max r = 0.73), coinciding with influenza hospital admissions (max r = 0.88) and lagging influenza test positivity (max r = 0.88). The majority of ILI reported to FluSurvey do not contact healthcare due to symptoms but experienced wider impacts on daily life. FluSurvey ILI corresponds well with other national influenza surveillance and provides broader context on community illness, supplementing the monitoring of influenza activity for public health response. Author summary: Understanding recent trends and characteristics of influenza-like illness (ILI) in the community can provide insights into the broader population burden of respiratory illness and provide context for other surveillance systems. We used FluSurvey, a UK participatory surveillance system, to characterise ILI over two winter seasons. We found that ILI was common and frequently impacted daily routine. A large proportion of ILI episodes were associated with missing work and school, reduced self-reported health, and medication use. Only a minority reported healthcare contact as a result of their symptoms. We then examined relationships of FluSurvey ILI with established influenza surveillance indicators, including GP ILI consultations, hospital admissions, and test positivity. Despite capturing illness primarily outside of healthcare settings, FluSurvey ILI rates strongly aligned with these indicators, with similar timing of seasonal activity. These findings provide insight on the impacts of ILI among the FluSurvey cohort, highlighting that most reported illness does not result in healthcare contact but does disrupt daily routine, including absenteeism. FluSurvey captures information that is not routinely available through healthcare-based surveillance, providing valuable context on trends and characteristics of illness outside of healthcare settings.
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BibTeX
@article{green2026monitoring,
title = {{Monitoring influenza-like symptoms in the UK through participatory surveillance: Insights from FluSurvey over two winter seasons (2023-24 and 2024-25)}},
author = {Rebecca E. Green and Jonathon Mellor and Christopher Rawlinson and Elizabeth Waller and Nurin Abdul Aziz and Conall H. Watson and Gavin Dabrera},
journal = {PLOS Digital Health},
year = {2026},
month = oct,
doi = {10.1371/journal.pdig.0001714},
url = {https://journals.plos.org/digitalhealth/article?id=10.1371/journal.pdig.0001714},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Monitoring influenza-like symptoms in the UK through participatory surveillance: Insights from FluSurvey over two winter seasons (2023-24 and 2024-25)
AU - Rebecca E. Green
AU - Jonathon Mellor
AU - Christopher Rawlinson
AU - Elizabeth Waller
AU - Nurin Abdul Aziz
AU - Conall H. Watson
AU - Gavin Dabrera
PY - 2026
DA - 2026/10/08
JO - PLOS Digital Health
DO - 10.1371/journal.pdig.0001714
UR - https://journals.plos.org/digitalhealth/article?id=10.1371/journal.pdig.0001714
AB - FluSurvey is a participatory surveillance system used to monitor trends in influenza and other respiratory viruses through weekly symptom surveys among the UK population. We aimed to characterise the wider impact of “influenza-like illnesses” (ILI) among FluSurvey participants and assess correlations of ILI with other established influenza surveillance systems. We included data reported by FluSurvey participants over the 2023–24 and 2024–25 winter seasons. Using weekly symptoms surveys, we derived ILI episodes and estimated the proportion reporting healthcare service use, medication use, impact on daily life, absenteeism and use of tests. We applied existing methodologies (omitting first report and weighting to the age-sex structure of England) and assessed cross-correlations of weekly FluSurvey ILI rates with the national surveillance of GP ILI consultations, influenza hospital admissions, and influenza PCR test positivity at time lags of up to +/-2 weeks. There were 3057 participants over two winter seasons (N2023-24 = 2540, 63% female, mean age 60 years; N2024-25 = 2273, 64% female, mean age 61 years). Of 1868 ILI episodes, only a minority contacted healthcare services (14%, most frequently visiting the GP). A large proportion of episodes reported medication use (89%), impact on daily life (75%) and missing school or work (47%). Testing frequency notably declined in the 2024–25 season compared to 2023–24. FluSurvey ILI rates were strongly correlated with other influenza surveillance, predominantly leading GP ILI consultations (max r = 0.73), coinciding with influenza hospital admissions (max r = 0.88) and lagging influenza test positivity (max r = 0.88). The majority of ILI reported to FluSurvey do not contact healthcare due to symptoms but experienced wider impacts on daily life. FluSurvey ILI corresponds well with other national influenza surveillance and provides broader context on community illness, supplementing the monitoring of influenza activity for public health response. Author summary: Understanding recent trends and characteristics of influenza-like illness (ILI) in the community can provide insights into the broader population burden of respiratory illness and provide context for other surveillance systems. We used FluSurvey, a UK participatory surveillance system, to characterise ILI over two winter seasons. We found that ILI was common and frequently impacted daily routine. A large proportion of ILI episodes were associated with missing work and school, reduced self-reported health, and medication use. Only a minority reported healthcare contact as a result of their symptoms. We then examined relationships of FluSurvey ILI with established influenza surveillance indicators, including GP ILI consultations, hospital admissions, and test positivity. Despite capturing illness primarily outside of healthcare settings, FluSurvey ILI rates strongly aligned with these indicators, with similar timing of seasonal activity. These findings provide insight on the impacts of ILI among the FluSurvey cohort, highlighting that most reported illness does not result in healthcare contact but does disrupt daily routine, including absenteeism. FluSurvey captures information that is not routinely available through healthcare-based surveillance, providing valuable context on trends and characteristics of illness outside of healthcare settings.
SN - 2767-3170
ER -