Reconstructing Mayotte 2018–19 Rift Valley Fever outbreak in humans by combining serological and surveillance data

Jonathan Bastard (1) , Guillaume André Durand (2, 3) , Fanny Parenton (1) , Youssouf Hassani (1) , Laure Dommergues (4) , Juliette Paireau (1, 5) , Nathanaël Hozé (5) , Marc Ruello (1) , Gilda Grard (2, 3) , Raphaëlle Métras (6) , Harold Noël (1)

1 Santé publique France - French National Public Health Agency [Saint-Maurice, France]
2 IRBA - Institut de Recherche Biomédicale des Armées [Antenne Marseille]
3 UVE - Unité des Virus Emergents
4 GDS 976 - Groupement de Défense Sanitaire Mayotte
5 Modélisation mathématique des maladies infectieuses - Mathematical modelling of Infectious Diseases
6 iPLESP - Institut Pierre Louis d'Epidémiologie et de Santé Publique

Background: Rift Valley Fever (RVF) is a zoonosis that affects large parts of Africa and the Arabian Peninsula. RVF virus (RVFV) is transmitted to humans through contacts with infected animals, animal products, mosquito bites or aerosols. Its pathogenesis in humans ranges from asymptomatic forms to potentially deadly haemorrhagic fevers, and the true burden of human infections during outbreaks is generally unknown. Methods: We build a model fitted to both passive surveillance data and serological data collected throughout a RVF epidemic that occurred in Mayotte Island in 2018–2019. Results: We estimate that RVFV infected 10,797 (95% CrI 4,728–16,127) people aged ≥15 years old in Mayotte during the entire outbreak, among which only 1.2% (0.67%–2.2%) were reported to the syndromic surveillance system. RVFV IgG seroprevalence in people ≥15 years old was estimated to increase from 5.5% (3.6%–7.7%) before the outbreak to 12.9% (10.4%–16.3%) thereafter. Conclusions: Our results suggest that a large part of RVFV infected people present subclinical forms of the disease and/or do not reach medical care that could lead to their detection by the surveillance system. This may threaten the implementation of exhaustive RVF surveillance and adequate control programs in affected countries.

Domaines: Santé publique et épidémiologie

Jonathan Bastard, Guillaume André Durand, Fanny Parenton, Youssouf Hassani, Laure Dommergues, et al.. Reconstructing Mayotte 2018–19 Rift Valley Fever outbreak in humans by combining serological and surveillance data. Communications Medicine, 2022, 2, pp.163. ⟨10.1038/s43856-022-00230-4⟩. ⟨pasteur-03926740⟩