Seasonal Influenza in Morocco
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Abstract
Influenza is an acute respiratory infection caused by influenza viruses of the Orthomyxoviridae family. Influenza virus cell culture consists of inoculating viral isolates on an MDCK cell layer. The objective of this work is to describe the role of cell culture in influenza virus subtyping during the 2023/2024 influenza epidemic at the Mohammed V Military Teaching Hospital - Rabat.
This is a prospective descriptive study carried out at the Virology laboratory of the HMIMV in Rabat, during the 2023/2024 influenza epidemic season (between October and May). It included all samples from patients positive for influenza viruses by the respiratory PCR test. Of the 86 samples positive by PCR, 36 were selected for viral culture.
Cell culture allowed the isolation of the virus from the original sample, thus producing a sufficient quantity for further antigenic and genetic characterization, allowing the subtyping of circulating strains.
The results showed a predominance of influenza A(H3N2) with 35 cases out of 36 compared to influenza A(H1N1) pdm09 with only 1 case.
Cell culture also makes it possible to assess the sensitivity of isolated viral strains to antiviral molecules and to detect the emergence of resistance. Thus, it plays an important role in virological surveillance and in alerting to the event of the appearance of new viruses.
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Copyright (c) 2025 El-Kochri S, et al.

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Jester B, Uyeki TM, Jernigan DB, Tumpey TM. Historical and clinical aspects of the 1918 H1N1 pandemic in the United States. Virology. 2019;527:32–7. Available from: https://doi.org/10.1016/j.virol.2018.10.019
Johnson NPAS, Mueller J. Updating the accounts: global mortality of the 1918-1920 “Spanish” influenza pandemic. Bull Hist Med. 2002;76(1):105–15. Available from: https://doi.org/10.1353/bhm.2002.0022
Viboud C, Simonsen L, Fuentes R, Flores J, Miller MA, Chowell G. Global mortality impact of the 1957–1959 influenza pandemic. J Infect Dis. 2016;213(5):738–45. Available from: https://doi.org/10.1093/infdis/jiv534
Centers for Disease Control and Prevention (CDC). 1968 Pandemic (H3N2 virus) | Pandemic Influenza (Flu). 2024. Available from: https://archive.cdc.gov/www_cdc_gov/flu/pandemic-resources/1968-pandemic.html
Mena I, Nelson MI, Quezada-Monroy F, Dutta J, Cortes-Fernández R, Lara-Puente JH, et al. Origins of the 2009 H1N1 influenza pandemic in swine in Mexico. eLife. 2016;5:e16777. Available from: https://doi.org/10.7554/eLife.16777
Dawood FS, Reed C, Meltzer MI, Shay DK, Cheng PY. Estimated global mortality associated with the first 12 months of 2009 pandemic influenza A H1N1 virus circulation: a modelling study. Lancet Infect Dis. 2012;12(9):687–95. Available from: https://doi.org/10.1016/s1473-3099(12)70121-4
World Health Organization (WHO). Grippe saisonnière. 2024. Available from: https://www.who.int/fr/news-room/fact-sheets/detail/influenza-(seasonal)
Duwe S. Influenza viruses – antiviral therapy and resistance. GMS Infect Dis. 2017;5:Doc04. Available from: https://doi.org/10.3205/id000030
Kommandantvold SA, Lemenuel-Diot A, Skedgel C, Pitman R, Rouse P. A cost-effectiveness analysis of reduced viral transmission with baloxavir marboxil versus oseltamivir or no treatment for seasonal and pandemic influenza management in the United Kingdom. Expert Rev Pharmacoecon Outcomes Res. 2024;24(8):953–66. Available from: https://doi.org/10.1080/14737167.2024.2365421
Ison MG, Yoshida Y, Shishido T, Mitchener M. Early treatment with baloxavir marboxil in high-risk adolescent and adult outpatients with uncomplicated influenza (CAPSTONE-2): a randomised, placebo-controlled, phase 3 trial. Lancet Infect Dis. 2020;20(10):1204–14. Available from: https://doi.org/10.1016/s1473-3099(20)30004-9
Administrator. Vaccins antigrippaux. World Health Organization - Regional Office for the Eastern Mediterranean. 2024. Available from: http://www.emro.who.int/fr/health-topics/influenza/influenza-vaccines.html
Nuwarda RF, Alharbi AA, Kayser V. An Overview of Influenza Viruses and Vaccines. Vaccines. 2021;9(9):1032. Available from: https://doi.org/10.3390/vaccines9091032
Barer MR. Medical Microbiology. 2018. Available from: https://shop.elsevier.com/books/medical-microbiology/barer/978-0-7020-7200-0
Masson E. Culture cellulaire et virologie. Intérêts et applications de la culture cellulaire en virologie. EM-Consulte. 2024. Available from: https://www.em-consulte.com/article/263914/culture-cellulaire-et-virologie-interets-et-applic
[Xpert Xpress SARS-CoV-2 Flu RSV HC IVD FRENCH Package Insert 302-5707-FR Rev. A.pdf].
World Health Organization. Manual for the laboratory diagnosis and virological surveillance of influenza. WHO Global Influenza Surveillance Network. 2011. Available from: https://iris.who.int/handle/10665/44518
Cai M, Gong Z, Dong T, Liu B, Su M, Li X. Production, Passaging Stability, and Histological Analysis of Madin–Darby Canine Kidney Cells Cultured in a Low-Serum Medium. Vaccines. 2024;12(9):Art. no. 9. Available from: https://doi.org/10.3390/vaccines12090991
Gamblin SJ, Vachieri SG, Xiong X, Zhang J, Martin SR, Skehel JJ. Hemagglutinin Structure and Activities. Cold Spring Harb Perspect Med. 2021;11(10):a038638. Available from: https://doi.org/10.1101/cshperspect.a038638
Medeiros R, Escriou N, Naffakh N, Manuguerra JC, Van Der Werf S. Hemagglutinin Residues of Recent Human A(H3N2) Influenza Viruses That Contribute to the Inability to Agglutinate Chicken Erythrocytes. Virology. 2001;289(1):74–85. Available from: https://doi.org/10.1006/viro.2001.1121
Lin YP, Collins P, Kloess J, Wharton S, Cattle N. Neuraminidase Receptor Binding Variants of Human Influenza A(H3N2) Viruses Resulting from Substitution of Aspartic Acid 151 in the Catalytic Site: a Role in Virus Attachment? J Virol. 2010;84(13):6769–81. Available from: https://doi.org/10.1128/jvi.00458-10
Javanian M, Barary M, Ghebrehewet S, Koppolu V, Vasigala V, Ebrahimpour S. A brief review of influenza virus infection. J Med Virol. 2021;93(8):4638–46. Available from: https://doi.org/10.1002/jmv.26990
Liu R, Sheng Z, Huang C, Wang D, Li F. Influenza D virus. Curr Opin Virol. 2020;44:154–61. Available from: https://doi.org/10.1016/j.coviro.2020.08.004
World Health Organization (WHO). Influenza (Seasonal). 2024. Available from: https://www.who.int/news-room/fact-sheets/detail/influenza-(seasonal)
Zeno EE, Regan A, Couto P, Rondy M, Jara J, Voto C. Interim Effectiveness Estimates of 2024 Southern Hemisphere Influenza Vaccines in Preventing Influenza-Associated Hospitalization — REVELAC-i Network, Five South American Countries, March–July 2024. MMWR Morb Mortal Wkly Rep. 2024;73(39):861–8. Available from: https://doi.org/10.15585/mmwr.mm7339a1
Bedford T, Suchard MA, Lemey P, Dudas G, Gregory V, Hay AJ, et al. Integrating influenza antigenic dynamics with molecular evolution. arXiv. 2013. Available from: https://doi.org/10.48550/arXiv.1304.3637
[Epidemiological Bulletin for Influenza and Severe Acute Respiratory Infections, 2023-24 season.pdf].
Seasonal influenza, 2023−2024, Annual Epidemiological Report, 2023. Available from: https://www.ecdc.europa.eu/en/publications-data/seasonal-influenza-annual-epidemiological-report-20232024
Centers for Disease Control and Prevention (CDC). 2023-2024 Influenza Season Summary: Influenza Severity Assessment, Burden and Burden Prevented. 2024. Available from: https://www.cdc.gov/flu/whats-new/flu-summary-addendum-2023-2024.html
[flunetchart]. Available from: https://worldhealthorg.shinyapps.io/flunetchart/
Influenza virus characterization - Summary Europe, March 2024. Available from: https://www.ecdc.europa.eu/en/publications-data/influenza-virus-characterization-summary-europe-march-2024
Recherche de « Vaccins » - Medicament.ma. Available from: https://medicament.ma/?choice=classeTherapeutique&s=15229
Seasonal flu vaccine: 400,000 doses between the public and private markets in 2023. Le Matin.ma. 2024. Available from: https://lematin.ma/societe/vaccin-contre-la-grippe-400000-doses-entre-le-marche-public-et-prive/202359
Announcement of recommendations for the composition of the influenza vaccine for the 2023-2024 influenza season in the Northern Hemisphere. Available from: https://www.who.int/fr/news/item/24-02-2023-recommendations-announced-for-influenza-vaccine-composition-for-the-2023-2024-northern-hemisphere-influenza-season
Announcement of recommendations for the composition of influenza vaccines for the 2024-2025 influenza season in the Northern Hemisphere. Available from: https://www.who.int/fr/news/item/23-02-2024-recommendations-announced-for-influenza-vaccine-composition-for-the-2024-2025-northern-hemisphere-influenza-season
Centers for Disease Control and Prevention (CDC). How Influenza (Flu) Vaccines Are Made. 2024. Available from: https://www.cdc.gov/flu/vaccine-process/index.html
Skowronski DM, De Serres G, Sabaiduc S, Eshaghi A, Dickinson JA. Low 2012–13 Influenza Vaccine Effectiveness Associated with Mutation in the Egg-Adapted H3N2 Vaccine Strain Not Antigenic Drift in Circulating Viruses. PLoS One. 2014;9(3):e92153. Available from: https://doi.org/10.1371/journal.pone.0092153
Barr IG, Katz JM, McCauley JW, Odagiri T. Cell culture-derived influenza vaccines in the severe 2017–2018 epidemic season: a step towards improved influenza vaccine effectiveness. NPJ Vaccines. 2018;3(1):44. Available from: https://doi.org/10.1038/s41541-018-0079-z
Hegde NR. Cell culture-based influenza vaccines: A necessary and indispensable investment for the future. Hum Vaccin Immunother. 2015;11(5):1223–34. Available from: https://doi.org/10.1080/21645515.2015.1016666
Zost SJ, Gumina ME, Kim K, Diaz Perez S, Wilson PC. Contemporary H3N2 influenza viruses have a glycosylation site that alters binding of antibodies elicited by egg-adapted vaccine strains. Proc Natl Acad Sci USA. 2017;114(47):12578–83. Available from: https://doi.org/10.1073/pnas.1712377114
Centers for Disease Control and Prevention (CDC). Influenza Activity in the United States during the 2023–2024 Season and Composition of the 2024–2025 Influenza Vaccine. 2024. Available from: https://www.cdc.gov/flu/whats-new/flu-summary-2023-2024.html
Centers for Disease Control and Prevention (CDC). Antigenic Characterization. 2024. Available from: https://www.cdc.gov/flu/php/viruses/antigenic.html