Influence of Both La Nina and Island Isolation During COVID-19 on the Epidemiology of Infectious Diseases in New Caledonia

Article Article scientifique Article Influence of Both La Nina and Island Isolation During COVID-19 on the Epidemiology of Infectious Diseases in New Caledonia eng 2026-05-21 author Moury Pierre-Henri 428541 Institut de santé globale (COSPR) author Gourinat Ann-Claire author Suveges Mária 717683 Mária Sueveges author Delrieu Méryl 0000-0002-8316-7783 author Dupont-Rouzeyrol Myrielle 0000-0002-6991-4893 author Menkes Christophe 0000-0002-1457-9696 author Soler Nathanaëlle 0000-0002-1006-5858 author Cazorla Cécile 0000-0003-1080-657X author Biron Antoine 0000-0003-1756-7655 author Flahault Antoine 0000-0002-6957-2977 815316 Décanat et administration de la faculté de médecine (ADMED) author Mangeas Morgan 0000-0003-4146-3784 author Ray Nicolas 0000-0002-4696-5313 126189 Institut de santé globale (COSPR) 70 10.3390/epidemiologia7030070 42201214 2673-3986 PMC13214734 https://www.mdpi.com/2673-3986/7/3/70 Background and Objectives: New Caledonia, an archipelago in the South Pacific, experienced an unprecedented conjunction of prolonged border closure during the COVID-19 pandemic (2020 to 2022) and marked influence of the El Niño/Southern Oscillation (ENSO). This context provided a unique opportunity to explore how environmental drivers, island isolation, and socio-demographic factors interact to shape infectious disease dynamics. This study aimed to assess the respective and combined effects of climatic variability, travel restrictions, and socio-demographic factors on the dynamics of four priority infectious diseases. Materials and Methods: We retrospectively analysed data from 2017 to 2023 on four infectious diseases: leptospirosis, dengue, influenza, and hepatitis A (HAV). Satellite precipitation data and the Multivariate El Niño/Southern Oscillation Index (MEI) were used. Socio-demographic and economic variables were gathered. Statistical analyses employed descriptive analysis and Generalized Additive Mixed Models to evaluate the associations between climatic events, travel restrictions, and disease circulation using the communal level as a random effect and time (daily) as a spline effect. Results: We analysed 878 cases of leptospirosis, 165 of HAV, 6607 of influenza, and 7377 dengue cases. Influenza was associated with rainfall before lockdown (Odds Ratio (OR) 0.7, Confidence interval 95%, (CI95%), (0.6–0.8)) and disappeared during lockdown but resurged post-reopening losing its meteorological association. Dengue epidemics declined, coinciding with the Wolbachia program and border closure, and were associated with lower MEI (OR 0.78, CI95% (0.6–1) during the 2017 to 2020 period. HAV cases were correlated with the MEI (OR: 1.8, CI95% (1–3.3)). Leptospirosis cases were associated with cumulative rainfall (OR 1.12 (1.1–1.2)) and lower education (OR 1.04, CI95% (1–1.1)) and decreased with water supply (OR 0.7, CI95% (0.5–0.8)). Conclusions: Our findings highlight how climatic conditions, mobility restrictions, and socio-environmental inequities differentially shape infectious disease risks in island ecosystems. These results reinforce the need for integrated One Health surveillance that jointly addresses environmental change, social vulnerability, and infectious disease prevention. Water-borne diseases Vector-borne disease Travel Leptospirosis Dengue Influenza El Niño/Southern Oscillation ENSO Emergent infectious diseases Dewey 613 Dewey 333.7-333.9 66 Institut de santé globale 22A1 18 Institut des sciences de l'environnement 0DB false 941 ISE Pôle Informatique environnementale 1275 GeoHealth: approches géospatiales et environnementales en santé globale 1000 1057 TIGERS 907 Groupe Flahault Antoine 945 Epidemiologia 7 3 f9042f97-0580-4d47-b13c-56b3fc453308 Article (Published version) Public epidemiologia-07-00070.pdf 782796 application/pdf CC BY-4.0 ee175572225deefaaaf2214f677e101c909ab22cec71729cfe30eff0471922d0 03ff0ebd-163f-453d-b07b-76c0ac44f759 Supplemental data Public epidemiologia-4249715-supplementary.pdf 1388218 application/pdf d700d0b268c06a8ca48d70d66efa3655e59f235d3de60dae4bb6995ed325eb24 openAccess Faculté de médecine / Section de médecine clinique / Département de santé et médecine communautaires / Institut de santé globale Centres et instituts / Institut des sciences de l'environnement

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Influence of Both La Nina and Island Isolation During COVID-19 on the Epidemiology of Infectious Diseases in New Caledonia	Epidemiologia			2026	6	38

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Moury, Pierre-Henri