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We investigated a COVID-19 outbreak at a fire station in Marseille, France. Confirmed cases were defined as individuals with positive SARS-CoV-2 reverse transcription (RT)-PCR and/or neutralising antibodies. All 85 firefighters at work during the outbreak period were included after questioning and sampled for RT-PCR and viral neutralisation assay. Twenty-three firefighters were confirmed positive, 19 of them were symptomatic, and four asymptomatic cases were confirmed by virus neutralisation. A total of 22 firefighters had specific neutralising antibodies against SARS-CoV-2. Neutralising antibodies were found in four asymptomatic and 18 symptomatic cases. Eleven symptomatic cases had high titres (≥ 1:80). The earliest detection of neutralising antibodies was 7 days after symptom onset, and 80% had neutralising antibodies 15 days after onset. One viral culture was positive 13 days after onset. The attack rate was 27%. We identified two introductions of the virus in this outbreak, through a presymptomatic and a paucisymptomatic case. Asymptomatic cases were not the source of a third generation of cases, although they worked without wearing a mask, indicating that asymptomatic cases did not play a significant role in this outbreak. Management and strategy based on early research of clinical signs associated with self-quarantine was effective.


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  1. Wang Y, Wang Y, Chen Y, Qin Q. Unique epidemiological and clinical features of the emerging 2019 novel coronavirus pneumonia (COVID-19) implicate special control measures. J Med Virol. 2020;92(6):568-76.  https://doi.org/10.1002/jmv.25748  PMID: 32134116 
  2. Lauer SA, Grantz KH, Bi Q, Jones FK, Zheng Q, Meredith HR, et al. the incubation period of coronavirus disease 2019 (COVID-19) from publicly reported confirmed cases: estimation and application. Ann Intern Med. 2020;172(9):577-82.  https://doi.org/10.7326/M20-0504  PMID: 32150748 
  3. Furukawa NW, Brooks JT, Sobel J. Evidence supporting transmission of severe acute respiratory syndrome coronavirus 2 while presymptomatic or asymptomatic. Emerg Infect Dis. 2020;26(7):e201595.  https://doi.org/10.3201/eid2607.201595  PMID: 32364890 
  4. Huang L, Zhang X, Zhang X, Wei Z, Zhang L, Xu J, et al. Rapid asymptomatic transmission of COVID-19 during the incubation period demonstrating strong infectivity in a cluster of youngsters aged 16-23 years outside Wuhan and characteristics of young patients with COVID-19: A prospective contact-tracing study. J Infect. 2020;80(6):e1-13.  https://doi.org/10.1016/j.jinf.2020.03.006  PMID: 32283156 
  5. Muniz-Rodriguez K, Fung IC-H, Ferdosi SR, Ofori SK, Lee Y, Tariq A, et al. Severe acute respiratory syndrome coronavirus 2 transmission potential, Iran, 2020. Emerg Infect Dis. 2020;26(8):1915-7.  https://doi.org/10.3201/eid2608.200536  PMID: 32320641 
  6. Guo L, Ren L, Yang S, Xiao M, Chang D, Yang F, et al. Profiling early humoral response to diagnose novel coronavirus disease (COVID-19). Clin Infect Dis. 2020;71(15):778-85.  https://doi.org/10.1093/cid/ciaa310  PMID: 32198501 
  7. Grifoni A, Weiskopf D, Ramirez SI, Mateus J, Dan JM, Moderbacher CR, et al. Targets of T cell responses to SARS-CoV-2 coronavirus in humans with COVID-19 disease and unexposed individuals. Cell. 2020;181(7):1489-1501.e15.  https://doi.org/10.1016/j.cell.2020.05.015  PMID: 32473127 
  8. Zhou G, Zhao Q. Perspectives on therapeutic neutralizing antibodies against the Novel Coronavirus SARS-CoV-2. Int J Biol Sci. 2020;16(10):1718-23.  https://doi.org/10.7150/ijbs.45123  PMID: 32226289 
  9. Liu W, Fontanet A, Zhang P-H, Zhan L, Xin Z-T, Baril L, et al. Two-year prospective study of the humoral immune response of patients with severe acute respiratory syndrome. J Infect Dis. 2006;193(6):792-5.  https://doi.org/10.1086/500469  PMID: 16479513 
  10. Chandrashekar A, Liu J, Martinot AJ, McMahan K, Mercado NB, Peter L, et al. SARS-CoV-2 infection protects against rechallenge in rhesus macaques. Science. 2020;369(6505):812-7.  https://doi.org/10.1126/science.abc4776  PMID: 32434946 
  11. European Centre for Disease Prevention and Control (ECDC). Communicable disease threats report. Week 11, 8-14 March 2020. Stockholm: ECDC; 2020. Available from: https://www.ecdc.europa.eu/sites/default/files/documents/Communicable-disease-threats-report-14-mar-2020.pdf
  12. Haut Conseil de la Santé Publique (HCSP). Avis relatif aux critères de sortie d’isolement des patients ayant été infectés par le SARS-CoV-2. [Notice relating to the criteria for discharge from isolation of patients infected with SARS-CoV-2]. Paris: HCSP; 2020 . French. Available from: https://www.hcsp.fr/Explore.cgi/Telecharger?NomFichier=hcspa20200316_corsarcovcriclidesordisodespatin.pdf
  13. Corman VM, Landt O, Kaiser M, Molenkamp R, Meijer A, Chu DK, et al. Detection of 2019 novel coronavirus (2019-nCoV) by real-time RT-PCR. Euro Surveill. 2020;25(3):e.  https://doi.org/10.2807/1560-7917.ES.2020.25.3.2000045  PMID: 31992387 
  14. Okba NMA, Müller MA, Li W, Wang C, GeurtsvanKessel CH, Corman VM, et al. severe acute respiratory syndrome coronavirus 2-specific antibody responses in coronavirus disease patients. Emerg Infect Dis. 2020;26(7):1478-88.  https://doi.org/10.3201/eid2607.200841  PMID: 32267220 
  15. Korber B, Fischer WM, Gnanakaran S, Yoon H, Theiler J, Abfalterer W, et al. Tracking changes in SARS-CoV-2 spike: evidence that D614G increases infectivity of the COVID-19 virus. Cell. 2020;182(4):812-827.e19.  https://doi.org/10.1016/j.cell.2020.06.043  PMID: 32697968 
  16. Liu Y, Funk S, Flasche S, Centre for Mathematical Modelling of Infectious Diseases nCoV Working Group. The contribution of pre-symptomatic infection to the transmission dynamics of COVID-2019. Wellcome Open Res. 2020;5:58.  https://doi.org/10.12688/wellcomeopenres.15788.1  PMID: 32685697 
  17. Buitrago-Garcia D, Egli-Gany D, Counotte MJ, Hossmann S, Imeri H, Ipekci AM, et al. Occurrence and transmission potential of asymptomatic and presymptomatic SARS-CoV-2 infections: A living systematic review and meta-analysis. PLoS Med. 2020;17(9):e1003346.  https://doi.org/10.1371/journal.pmed.1003346  PMID: 32960881 
  18. He X, Lau EHY, Wu P, Deng X, Wang J, Hao X, et al. Temporal dynamics in viral shedding and transmissibility of COVID-19. Nat Med. 2020;26(5):672-5.  https://doi.org/10.1038/s41591-020-0869-5  PMID: 32296168 
  19. Maltezou HC, Vorou R, Papadima K, Kossyvakis A, Spanakis N, Gioula G, et al. Transmission dynamics of SARS-CoV-2 within families with children in Greece: A study of 23 clusters. J Med Virol. 2021;93(3):1414-20.  https://doi.org/10.1002/jmv.26394  PMID: 32767703 
  20. Centre d’Epidémiologie et de Santé Publique des Armées (CESPA). Rapport d’investigation de l’épidémie de COVID-19 au sein du groupe aéronaval, 21 janvier-13 avril 2020. [Report on the investigation of the COVID-19 epidemic within the aeronaval service, 21 January to 13 April 2020]. Marseille: CESPA; 2020. French. Available from: https://www.defense.gouv.fr/content/download/583466/9938746/file/20200405_929_ARM_SSA_CESPA_rapport_epidemie_covid19_Gan_VEXP.pdf
  21. Long Q-X, Liu B-Z, Deng H-J, Wu G-C, Deng K, Chen Y-K, et al. Antibody responses to SARS-CoV-2 in patients with COVID-19. Nat Med. 2020;26(6):845-8.  https://doi.org/10.1038/s41591-020-0897-1  PMID: 32350462 
  22. Choe PG, Kang CK, Suh HJ, Jung J, Kang E, Lee SY, et al. Antibody responses to SARS-CoV-2 at 8 weeks postinfection in asymptomatic patients. Emerg Infect Dis. 2020;26(10):2484-7.  https://doi.org/10.3201/eid2610.202211  PMID: 32579877 

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