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Since the onset of the COVID-19 pandemic, the disease has frequently been compared with seasonal influenza, but this comparison is based on little empirical data.


This study compares in-hospital outcomes for patients with community-acquired COVID-19 and patients with community-acquired influenza in Switzerland.


This retrospective multi-centre cohort study includes patients > 18 years admitted for COVID-19 or influenza A/B infection determined by RT-PCR. Primary and secondary outcomes were in-hospital mortality and intensive care unit (ICU) admission for patients with COVID-19 or influenza. We used Cox regression (cause-specific and Fine-Gray subdistribution hazard models) to account for time-dependency and competing events with inverse probability weighting to adjust for confounders.


In 2020, 2,843 patients with COVID-19 from 14 centres were included. Between 2018 and 2020, 1,381 patients with influenza from seven centres were included; 1,722 (61%) of the patients with COVID-19 and 666 (48%) of the patients with influenza were male (p < 0.001). The patients with COVID-19 were younger (median 67 years; interquartile range (IQR): 54–78) than the patients with influenza (median 74 years; IQR: 61–84) (p < 0.001). A larger percentage of patients with COVID-19 (12.8%) than patients with influenza (4.4%) died in hospital (p < 0.001). The final adjusted subdistribution hazard ratio for mortality was 3.01 (95% CI: 2.22–4.09; p < 0.001) for COVID-19 compared with influenza and 2.44 (95% CI: 2.00–3.00, p < 0.001) for ICU admission.


Community-acquired COVID-19 was associated with worse outcomes compared with community-acquired influenza, as the hazards of ICU admission and in-hospital death were about two-fold to three-fold higher.


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  1. Molina B. Facebook pulls Trump post comparing COVID-19 to flu; Twitter adds warning. Geneva: USA Today. 6 Oct 2020. Available from: https://eu.usatoday.com/story/tech/2020/10/06/trump-post-covid-19-draws-removal-facebook-gets-twitter-warning/3637613001/
  2. Beer T. All The Times Trump Compared Covid-19 To The Flu, Even After He Knew Covid-19 Was Far More Deadly. Jersey. Forbes. 2020;10. Available from: https://www.forbes.com/sites/tommybeer/2020/09/10/all-the-times-trump-compared-covid-19-to-the-flu-even-after-he-knew-covid-19-was-far-more-deadly/?sh=35168c77f9d2
  3. World Health Organization (WHO). Q&As on COVID-19 and related health topics. Coronavirus disease (COVID-19): similarities and differences between COVID-19 and Influenza. Geneva: WHO; 30 Sep 2020. Available from: https://www.who.int/emergencies/diseases/novel-coronavirus-2019/question-and-answers-hub/coronavirus-disease-covid-19-similarities-and-differences-with-influenza
  4. Petersen E, Koopmans M, Go U, Hamer DH, Petrosillo N, Castelli F, et al. Comparing SARS-CoV-2 with SARS-CoV and influenza pandemics. Lancet Infect Dis. 2020;20(9):e238-44.  https://doi.org/10.1016/S1473-3099(20)30484-9  PMID: 32628905 
  5. The World Bank. The Global Economic Outlook During the COVID-19 Pandemic: A Changed World. Washington: The World Bank; 8 Jun 2020. Available from: https://www.worldbank.org/en/news/feature/2020/06/08/the-global-economic-outlook-during-the-covid-19-pandemic-a-changed-world
  6. Bundesamt für Gesundheit BAG. Saisonale Grippe 2011/2012: Zeit, sich impfen zu lassen. [Seasonal influenza 2011/2012: Time to get vaccinated]. BAG Bulletin. 2011;42:899-901. German. Available from: https://www.infovac.ch/de/?option=com_gd&view=listing&fid=706&task=ofile
  7. John Hopkins University. Coronavirus map. Baltimore: Johns Hopkins University. [Accessed: 28 Jul 2021]. Available from: https://coronavirus.jhu.edu/map.html
  8. Bundesamt für Gesundheit BAG. Dashboard. Bern: Bundesamt für Gesundheit BAG. 2021. German. Available from: https://www.covid19.admin.ch/de/overview
  9. Grein J, Ohmagari N, Shin D, Diaz G, Asperges E, Castagna A, et al. Compassionate Use of Remdesivir for Patients with Severe Covid-19. N Engl J Med. 2020;382(24):2327-36.  https://doi.org/10.1056/NEJMoa2007016  PMID: 32275812 
  10. Group RC, Horby P, Lim WS, Emberson JR, Mafham M, Bell JL, et al. Dexamethasone in Hospitalized Patients with Covid-19 - Preliminary Report. N Engl J Med. 2020.
  11. Elekhnawy E, Kamar AA, Sonbol F. Present and future treatment strategies for coronavirus disease 2019. Futur J Pharm Sci. 2021;7(1):84.  PMID: 33850936 
  12. Polack FP, Thomas SJ, Kitchin N, Absalon J, Gurtman A, Lockhart S, et al. Safety and Efficacy of the BNT162b2 mRNA Covid-19 Vaccine. N Engl J Med. 2020;383(27):2603-15.  https://doi.org/10.1056/NEJMoa2034577  PMID: 33301246 
  13. Faury H, Courboules C, Payen M, Jary A, Hausfater P, Luyt C, et al. Medical features of COVID-19 and influenza infection: A comparative study in Paris, France. J Infect. 2020. PMID: 32798533 
  14. Zayet S, Kadiane-Oussou NJ, Lepiller Q, Zahra H, Royer PY, Toko L, et al. Clinical features of COVID-19 and influenza: a comparative study on Nord Franche-Comte cluster. Microbes Infect. 2020;22(9):481-8.  https://doi.org/10.1016/j.micinf.2020.05.016  PMID: 32561409 
  15. Piroth L, Cottenet J, Mariet AS, Bonniaud P, Blot M, Tubert-Bitter P, et al. Comparison of the characteristics, morbidity, and mortality of COVID-19 and seasonal influenza: a nationwide, population-based retrospective cohort study. Lancet Respir Med. 2021;9(3):251-9.  https://doi.org/10.1016/S2213-2600(20)30527-0  PMID: 33341155 
  16. Xie Y, Bowe B, Maddukuri G, Al-Aly Z. Comparative evaluation of clinical manifestations and risk of death in patients admitted to hospital with covid-19 and seasonal influenza: cohort study. BMJ. 2020;371:m4677.  https://doi.org/10.1136/bmj.m4677  PMID: 33323357 
  17. University of Geneva. Hospital based surveillance of influenza in Switzerland - a pilot study. Geneva: University of Geneva. [Accessed: 24 Dec 2021]. Available from: https://www.unige.ch/medecine/hospital-flu/
  18. University of Geneva. Hospital based surveillance of Covid-19 in Switzerland. Geneva: University of Geneva. [Accessed: 24 Dec 2021]. Available from: https://www.unige.ch/medecine/hospital-covid/
  19. Lau B, Cole SR, Gange SJ. Competing risk regression models for epidemiologic data. Am J Epidemiol. 2009;170(2):244-56.  https://doi.org/10.1093/aje/kwp107  PMID: 19494242 
  20. Fine JP, Gray RJ. A Proportional Hazards Model for the Subdistribution of a Competing Risk. J Am Stat Assoc. 1999;94(446):496-509.  https://doi.org/10.1080/01621459.1999.10474144 
  21. Statista. Number of hospitalizations due to the coronavirus (COVID-19) in Switzerland in 2020. New York: Statista. [Accessed: 24 Dec 2021]. Available from: https://www.statista.com/statistics/1110045/coronavirus-covid-19-hospitalizations-number-age-group-switzerland/
  22. Kerr S, Felling M, Jordan D. Is It Like the Flu? Is It a Major Threat? Trump’s Changing Coronavirus Message. New York: New York Times. 3 Apr 2020. Available from: https://www.nytimes.com/video/us/politics/100000007067717/trumps-coronavirus-statements.html
  23. Walsh NP, Shelley J, Duwe E, Bonnett W. Bolsonaro calls coronavirus a 'little flu'. Atlanta: CNN; 25 May 2020. Available from: https://edition.cnn.com/2020/05/23/americas/brazil-coronavirus-hospitals-intl/index.html
  24. von der Beck D, Seeger W, Herold S, Günther A, Löh B. Characteristics and outcomes of a cohort hospitalized for pandemic and seasonal influenza in Germany based on nationwide inpatient data. PLoS One. 2017;12(7):e0180920.  https://doi.org/10.1371/journal.pone.0180920  PMID: 28708896 
  25. Wang D, Hu B, Hu C, Zhu F, Liu X, Zhang J, et al. Clinical Characteristics of 138 Hospitalized Patients With 2019 Novel Coronavirus-Infected Pneumonia in Wuhan, China. JAMA. 2020;323(11):1061-9.  https://doi.org/10.1001/jama.2020.1585  PMID: 32031570 
  26. Zhou F, Yu T, Du R, Fan G, Liu Y, Liu Z, et al. Clinical course and risk factors for mortality of adult inpatients with COVID-19 in Wuhan, China: a retrospective cohort study. Lancet. 2020;395(10229):1054-62.  https://doi.org/10.1016/S0140-6736(20)30566-3  PMID: 32171076 
  27. Mondal S, Quintili AL, Karamchandani K, Bose S. Thromboembolic disease in COVID-19 patients: A brief narrative review. J Intensive Care. 2020;8(1):70.  https://doi.org/10.1186/s40560-020-00483-y  PMID: 32939266 
  28. Ding Q, Lu P, Fan Y, Xia Y, Liu M. The clinical characteristics of pneumonia patients coinfected with 2019 novel coronavirus and influenza virus in Wuhan, China. J Med Virol. 2020;92(9):1549-55.  https://doi.org/10.1002/jmv.25781  PMID: 32196707 
  29. Cuadrado-Payán E, Montagud-Marrahi E, Torres-Elorza M, Bodro M, Blasco M, Poch E, et al. SARS-CoV-2 and influenza virus co-infection. Lancet. 2020;395(10236):e84.  https://doi.org/10.1016/S0140-6736(20)31052-7  PMID: 32423586 

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