Franck de Laval1,2, Anaïs Grosset-Janin3, François Delon4,5, Alexandre Allonneau3, Christelle Tong4, Flavie Letois4, Anne Couderc3, Marc-Antoine Sanchez4, César Destanque3, Fabrice Biot6, Françoise Raynaud7, Christine Bigaillon8, Olivier Ferraris6, Etienne Simon-Loriere9, Vincent Enouf10,11, Dinaherisoa Andriamanantena8, Vincent Pommier de Santi4,12, Emilie Javelle12,13, Audrey Mérens8. 1. SSA (French Military Health Service), CESPA (French Armed Forces Center for Epidemiology and Public Health), Epidemiological Surveillance and Investigations Unit, BdD Marseille-Aubagne, 111 Avenue de la Corse, Marseille, 13568, France. f_de_laval@hotmail.com. 2. Aix-Marseille University, INSERM, IRD, SESSTIM (Economic and Social Sciences, Health Systems, and Medical Informatics), Marseille, France. f_de_laval@hotmail.com. 3. SSA (French Military Health Service), 1st Armed Forces Medical Center, Paris, France. 4. SSA (French Military Health Service), CESPA (French Armed Forces Center for Epidemiology and Public Health), Epidemiological Surveillance and Investigations Unit, BdD Marseille-Aubagne, 111 Avenue de la Corse, Marseille, 13568, France. 5. Aix-Marseille University, INSERM, IRD, SESSTIM (Economic and Social Sciences, Health Systems, and Medical Informatics), Marseille, France. 6. SSA (French Military Health Service), Armed Forces Biomedical Research Institute, Brétigny-sur-Orge, France. 7. Direction Générale de l'Armement, Maîtrise NRBC, Vert-le-Petit, France. 8. SSA (French Military Health Service), Bégin Military Teaching Hospital, Saint-Mandé, France. 9. G5 Evolutionary genomics of RNA viruses, Institut Pasteur, Paris, France. 10. National Reference Center for Respiratory Viruses, Molecular Genetics of RNA Viruses, Institut Pasteur, CNRS-UMR 3569, University of Paris, Paris, France. 11. Mutualized Platform of Microbiology, Pasteur International Bioresources Network, Institut Pasteur, Paris, France. 12. Aix-Marseille University, IRD, AP-HM, SSA (French Military Health Service), VITROME, Marseille, France. 13. SSA (French Military Health Service), Laveran Military Teaching Hospital, Marseille, France.
Abstract
BACKGROUND: This study presents the methods and results of the investigation into a SARS-CoV-2 outbreak in a professional community. Due to the limited testing capacity available in France at the time, we elaborated a testing strategy according to pre-test probability. METHODS: The investigation design combined active case finding and contact tracing around each confirmed case with testing of at-risk contact persons who had any evocative symptoms (n = 88). One month later, we performed serology testing to test and screen symptomatic and asymptomatic cases again (n = 79). RESULTS: Twenty-four patients were confirmed (14 with RT-PCR and 10 with serology). The attack rate was 29% (24/83). Median age was 40 (24 to 59), and the sex ratio was 15/12. Only three cases were asymptomatic (= no symptoms at all, 13%, 95% CI, 3-32). Nineteen symptomatic cases (79%, 95% CI, 63-95) presented a respiratory infection, two of which were severe. All the RT-PCR confirmed cases acquired protective antibodies. Median incubation was 4 days (from 1 to 13 days), and the median serial interval was 3 days (0 to 15). We identified pre-symptomatic transmission in 40% of this cluster, but no transmission from asymptomatic to symptomatic cases. CONCLUSION: We report the effective use of targeted testing according to pre-test probability, specifically prioritizing symptomatic COVID-19 diagnosis and contact tracing. The asymptomatic rate raises questions about the real role of asymptomatic infected people in transmission. Conversely, pre-symptomatic contamination occurred frequently in this cluster, highlighting the need to identify, test, and quarantine asymptomatic at-risk contact persons (= contact tracing). The local lockdown imposed helped reduce transmission during the investigation period.
BACKGROUND: This study presents the methods and results of the investigation into a SARS-CoV-2 outbreak in a professional community. Due to the limited testing capacity available in France at the time, we elaborated a testing strategy according to pre-test probability. METHODS: The investigation design combined active case finding and contact tracing around each confirmed case with testing of at-risk contact persons who had any evocative symptoms (n = 88). One month later, we performed serology testing to test and screen symptomatic and asymptomatic cases again (n = 79). RESULTS: Twenty-four patients were confirmed (14 with RT-PCR and 10 with serology). The attack rate was 29% (24/83). Median age was 40 (24 to 59), and the sex ratio was 15/12. Only three cases were asymptomatic (= no symptoms at all, 13%, 95% CI, 3-32). Nineteen symptomatic cases (79%, 95% CI, 63-95) presented a respiratory infection, two of which were severe. All the RT-PCR confirmed cases acquired protective antibodies. Median incubation was 4 days (from 1 to 13 days), and the median serial interval was 3 days (0 to 15). We identified pre-symptomatic transmission in 40% of this cluster, but no transmission from asymptomatic to symptomatic cases. CONCLUSION: We report the effective use of targeted testing according to pre-test probability, specifically prioritizing symptomatic COVID-19 diagnosis and contact tracing. The asymptomatic rate raises questions about the real role of asymptomatic infectedpeople in transmission. Conversely, pre-symptomatic contamination occurred frequently in this cluster, highlighting the need to identify, test, and quarantine asymptomatic at-risk contact persons (= contact tracing). The local lockdown imposed helped reduce transmission during the investigation period.
Authors: Joshua Quick; Nathan D Grubaugh; Steven T Pullan; Ingra M Claro; Andrew D Smith; Karthik Gangavarapu; Glenn Oliveira; Refugio Robles-Sikisaka; Thomas F Rogers; Nathan A Beutler; Dennis R Burton; Lia Laura Lewis-Ximenez; Jaqueline Goes de Jesus; Marta Giovanetti; Sarah C Hill; Allison Black; Trevor Bedford; Miles W Carroll; Marcio Nunes; Luiz Carlos Alcantara; Ester C Sabino; Sally A Baylis; Nuno R Faria; Matthew Loose; Jared T Simpson; Oliver G Pybus; Kristian G Andersen; Nicholas J Loman Journal: Nat Protoc Date: 2017-05-24 Impact factor: 13.491
Authors: Stephen M Kissler; Christine Tedijanto; Yonatan H Grad; Marc Lipsitch; Edward Goldstein Journal: Science Date: 2020-04-14 Impact factor: 47.728
Authors: Joel Hellewell; Sam Abbott; Amy Gimma; Nikos I Bosse; Christopher I Jarvis; Timothy W Russell; James D Munday; Adam J Kucharski; W John Edmunds; Sebastian Funk; Rosalind M Eggo Journal: Lancet Glob Health Date: 2020-02-28 Impact factor: 26.763