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Since 1996, epidemiological surveillance of acute respiratory infections (ARI) in Spain has been limited to seasonal influenza, respiratory syncytial virus (RSV) and potential pandemic viruses The COVID-19 pandemic provides opportunities to adapt existing systems for extended surveillance to capture a broader range of ARI.


To describe how the Influenza Sentinel Surveillance System of Castilla y León, Spain was rapidly adapted in 2020 to comprehensive sentinel surveillance for ARI, including influenza and COVID-19.


Using principles and methods of the health sentinel network, we integrated electronic medical record data from 68 basic surveillance units, covering 2.6% of the regional population between January 2020 to May 2022. We tested sentinel and non-sentinel samples sent weekly to the laboratory network for SARS-CoV-2, influenza viruses and other respiratory pathogens. The moving epidemic method (MEM) was used to calculate epidemic thresholds.


ARI incidence was estimated at 18,942 cases per 100,000 in 2020/21 and 45,223 in 2021/22, with similar seasonal fold increases by type of respiratory disease. Incidence of influenza-like illness was negligible in 2020/21 but a 5-week epidemic was detected by MEM in 2021/22. Epidemic thresholds for ARI and COVID-19 were estimated at 459.4 and 191.3 cases per 100,000 population, respectively. More than 5,000 samples were tested against a panel of respiratory viruses in 2021/22.


Extracting data from electronic medical records reported by trained professionals, combined with a standardised microbiological information system, is a feasible and useful method to adapt influenza sentinel reports to comprehensive ARI surveillance in the post-COVID-19 era.


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  1. Agencia Estatal. Boletín Oficial del Estado. Real Decreto 2210/1995, de 28 de diciembre, por el que se crea la red nacional de vigilancia epidemiológica. [Royal Decree 2210/1995 of 28 December 1995, establishing the national network for epidemiological surveillance.] Madrid: Ministerio de Sanidad y Consumo, Gobierno de España; 1996. Spanish. Available from: https://www.boe.es/eli/es/rd/1995/12/28/2210
  2. Fleming DM, van der Velden J, Paget WJ. The evolution of influenza surveillance in Europe and prospects for the next 10 years. Vaccine. 2003;21(16):1749-53.  https://doi.org/10.1016/S0264-410X(03)00066-5  PMID: 12686088 
  3. European Centre for Disease Prevention and Control (ECDC). European Influenza Surveillance Network (EISN). Stockholm: ECDC. [Accessed: 1 Jun 2022]. Available from: https://www.ecdc.europa.eu/en/about-us/partnerships-and-networks/disease-and-laboratory-networks/eisn
  4. Vega T, Lozano JE, Meerhoff T, Snacken R, Mott J, Ortiz de Lejarazu R, et al. Influenza surveillance in Europe: establishing epidemic thresholds by the moving epidemic method. Influenza Other Respir Viruses. 2013;7(4):546-58.  https://doi.org/10.1111/j.1750-2659.2012.00422.x  PMID: 22897919 
  5. European Centre for Disease Prevention and Control, World Health Organization Regional Office for Europe (WHO/Europe). Influenza surveillance country, territory and area profiles 2019. Copenhagen: WHO/Europe and Stockholm: ECDC; 2021. Available from: https://www.who.int/europe/publications/i/item/WHO-EURO-2019-3621-43380-60857
  6. Broberg E, Pereyaslov D, Struelens M, Palm D, Meijer A, Ellis J, et al. Laboratory preparedness in EU/EEA countries for detection of novel avian influenza A(H7N9) virus, May 2013. Euro Surveill. 2014;19(4):20682.  https://doi.org/10.2807/1560-7917.ES2014.19.4.20682  PMID: 24507469 
  7. Agencia Estatal. Boletín Oficial del Estado.Orden SSI/445/2015, de 9 de marzo, por la que se modifican los anexos I, II y III del Real Decreto 2210/1995, de 28 de diciembre, por el que se crea la Red Nacional de Vigilancia Epidemiológica, relativos a la lista de enfermedades de declaración obligatoria, modalidades de declaración y enfermedades endémicas de ámbito regional. [Order SSI/445/2015, of 9 March, amending Annexes I, II and III of Royal Decree 2210/1995 of 28 December establishing the national network for epidemiological surveillance, relating to the list of notifiable diseases, modalities of declaration and endemic diseases of regional scope.] Madrid: Ministerio de Sanidad, Servicios Sociales e Igualdad, Gobierno de España; 2015. Spanish. Available from: https://www.boe.es/eli/es/o/2015/03/09/ssi445
  8. World Health Organization (WHO). Pandemic influenza severity assessment (‎PISA)‎: a WHO guide to assess the severity of influenza in seasonal epidemics and pandemics. Geneva: WHO; ‎2017. Available from: https://apps.who.int/iris/handle/10665/259392
  9. Vega Alonso AT, Gil M, Ruiz Cosín C, Zapatero E. The sentinel physicians network of Castilla y León: application of cluster analysis to obtain a representative sample. Gac Sanit. 1990;4:184-8.  https://doi.org/10.1016/S0213-9111(90)71028-X  PMID: 2286498 
  10. Junta de Castilla y León. Informe de la Red Centinela Sanitaria de Castilla y León. Programa 2018. N° 106 (2919). [Report of the Health Sentinel Network of Castilla y León. Programme 2018. No 106 (2919)]. Valladolid: Junta de Castilla y León. [Accessed: 1 Jun 2022]. Spanish. Available from: https://www.saludcastillayleon.es/profesionales/es/centinelas/informes-boletines-red-centinela-sanitaria-castilla-leon.ficheros/1380662-Red%20Centinela%20106-WEB.pdf
  11. Vega Alonso AT, Zurriaga Llorens O, Galmés Truyols A, Lozano Alonso JE, Paisán Maestro L, Gil Costa M, et al. Guía de principios y métodos de las redes centinelas sanitarias en España. [Guide to the principles and methods of health sentinel networks in Spain]. Gac Sanit. 2006;20(Suppl 3):52-60. Spanish.  https://doi.org/10.1157/13101090  PMID: 17433201 
  12. Junta de Castilla y León. Programa de Vigilancia Integral de las IRA en Castilla y León. [Comprehensive Surveillance Programme of ARI in Castilla y León. [ARI Integrated Surveillance Program in Castilla y León]. Valladolid: Junta de Castilla y León; 2021. Spanish. Available from: https://www.saludcastillayleon.es/profesionales/es/centinelas/nuevo-programa-vigilancia-integrada-ira-red-centinela-sanit.ficheros/1991747-Programa%20VIGIRA%202021-22-v3.1.pdf
  13. Buda S, Tolksdorf K, Schuler E, Kuhlen R, Haas W, De B. Establishing an ICD-10 code based SARI-surveillance in Germany - description of the system and first results from five recent influenza seasons. BMC Public Health. 2017;17(1):612.  https://doi.org/10.1186/s12889-017-4515-1  PMID: 28666433 
  14. World Health Organization (WHO). WHO Regional Office for Europe guidance for sentinel influenza surveillance in humans. Geneva: WHO. [Accessed: 1 Jun 2022]. Available from: https://apps.who.int/iris/handle/10665/349780
  15. European Commission. Commission Implementing Decision (EU) 2021/788 of 12 May 2021 laying down rules for the monitoring and reporting of infections with SARS-CoV-2 in certain animal species. Official Journal of the European Union. Luxembourg: Publications Office of the European Union. 15.5.2021: L173. Available from: https://eur-lex.europa.eu/legal-content/EN/TXT/PDF/?uri=CELEX:32021D0788&from=GA
  16. European Centre for Disease Prevention and Control (ECDC). Case definition for COVID-19, as of 3 December 2020. Stockholm: ECDC; 2020. Available from: https://www.ecdc.europa.eu/en/covid-19/surveillance/case-definition
  17. Rinaldi E, Saas J, Thun S. Use of LOINC and SNOMED CT with FHIR for Microbiology Data. Stud Health Technol Inform. 2021;278:156-62.  https://doi.org/10.3233/SHTI210064  PMID: 34042889 
  18. Vega T, Lozano JE, Meerhoff T, Snacken R, Beauté J, Jorgensen P, et al. Influenza surveillance in Europe: comparing intensity levels calculated using the moving epidemic method. Influenza Other Respir Viruses. 2015;9(5):234-46.  https://doi.org/10.1111/irv.12330  PMID: 26031655 
  19. Junta de Castilla y León. Situación epidemiológica del coronavirus (COVID-19) en Castilla y León. [Epidemiological situation of coronavirus (COVID-19) in Castilla y León]. Valladolid: Junta de Castilla y León; 2022. Spanish. Available from: https://analisis.datosabiertos.jcyl.es/pages/coronavirus/
  20. Chu DK, Akl EA, Duda S, Solo K, Yaacoub S, Schünemann HJ, et al. Physical distancing, face masks, and eye protection to prevent person-to-person transmission of SARS-CoV-2 and COVID-19: a systematic review and meta-analysis. Lancet. 2020;395(10242):1973-87.  https://doi.org/10.1016/S0140-6736(20)31142-9  PMID: 32497510 
  21. Cowling BJ, Ali ST, Ng TWY, Tsang TK, Li JCM, Fong MW, et al. Impact assessment of non-pharmaceutical interventions against coronavirus disease 2019 and influenza in Hong Kong: an observational study. Lancet Public Health. 2020;5(5):e279-88.  https://doi.org/10.1016/S2468-2667(20)30090-6  PMID: 32311320 
  22. Lagacé-Wiens P, Sevenhuysen C, Lee L, Nwosu A, Smith T. Impact of nonpharmaceutical interventions on laboratory detections of influenza A and B in Canada. Can Commun Dis Rep. 2021;47(3):142-8.  https://doi.org/10.14745/ccdr.v47i03a04  PMID: 34012338 
  23. Junta de Castilla y León. Memoria del proyecto 'Incidencia de la Enfermedad COVID-19 y su impacto en el conjunto de las infecciones respiratorias agudas. Red centinela sanitaria de Castilla y León'. [Report of the project 'Incidence of COVID-19 and its impact on acute respiratory infections as a whole. Health Sentinel Network of Castilla y León’]. Valladolid: Junta de Castilla y León; 2022. Spanish. Available from https://www.saludcastillayleon.es/profesionales/es/centinelas/programa-vigilancia-integrada-ira-red-centinela-sanitaria-c/memoria-proyecto-incidencia-enfermedad-covid-19-impacto-con.ficheros/2146677-MEMORIA%20v4.pdf
  24. Guerrisi C, Turbelin C, Souty C, Poletto C, Blanchon T, Hanslik T, et al. The potential value of crowdsourced surveillance systems in supplementing sentinel influenza networks: the case of France. Euro Surveill. 2018;23(25):1700337.  https://doi.org/10.2807/1560-7917.ES.2018.23.25.1700337  PMID: 29945696 
  25. World Health Organization (WHO). Global epidemiological surveillance standards for influenza. Geneva: WHO; 2013. Available from: https://www.who.int/publications/i/item/9789241506601
  26. Aguilera JF, Paget WJ, van der Velden J. Development of a protocol to evaluate the quality of clinical influenza data collected by sentinel practitioners in Europe. Euro Surveill. 2002;7(11):158-60.  https://doi.org/10.2807/esm.07.11.00374-en  PMID: 12631988 
  27. Łuniewska K, Szymański K, Hallmann-Szelińska E, Kowalczyk D, Sałamatin R, Masny A, et al. Evaluation of the 2017/18 Influenza Epidemic Season in Poland Based on the SENTINEL Surveillance System. Adv Exp Med Biol. 2019;1222:63-8.  https://doi.org/10.1007/5584_2019_424  PMID: 31352577 
  28. Babakazo P, Kabamba-Tshilobo J, Wemakoy EO, Lubula L, Manya LK, Ilunga BK, et al. Evaluation of the influenza sentinel surveillance system in the Democratic Republic of Congo, 2012-2015. BMC Public Health. 2019;19(1):1652.  https://doi.org/10.1186/s12889-019-8008-2  PMID: 31823763 
  29. Simusika P, Tempia S, Chentulo E, Polansky L, Mazaba ML, Ndumba I, et al. An evaluation of the Zambia influenza sentinel surveillance system, 2011-2017. BMC Health Serv Res. 2020;20(1):35.  https://doi.org/10.1186/s12913-019-4884-5  PMID: 31931793 
  30. World Health Organization (WHO). Guidance for surveillance of SARS-CoV-2 variants: interim guidance, 9 August 2021. Geneva: WHO; 2021. Available from: https://apps.who.int/iris/handle/10665/343775
  31. Bagaria J, Jansen T, Marques DF, Hooiveld M, McMenamin J, de Lusignan S, et al. Rapidly adapting primary care sentinel surveillance across seven countries in Europe for COVID-19 in the first half of 2020: strengths, challenges, and lessons learned. Euro Surveill. 2022;27(26):2100864.  https://doi.org/10.2807/1560-7917.ES.2022.27.26.2100864  PMID: 35775429 
  32. World Health Organization Regional Office for Europe (WHO/Europe) and European Centre for Disease Prevention and Control (ECDC). Operational considerations for respiratory virus surveillance in Europe. Copenhagen: WHO/Europe and Stockholm: ECDC; 2022. Available from: https://www.who.int/europe/publications/i/item/WHO-EURO-2022-5841-45606-65427

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