Disentangling seasonal introduction and establishment risk of dengue in Africa

Background The dengue virus is a significant global public health concern that poses a threat to Africa. Particularly, African countries are at risk of viral introductions through air travel connectivity with areas of South America and Asia that experience frequent explosive outbreaks. Limited reporting and diagnostic capacity hinder a comprehensive assessment of continent-wide transmission dynamics and deployment of surveillance strategies in Africa. Methods The risk of dengue introduction into Africa from countries of high incidence was estimated based on origin-destination air travel flows and epidemic activity at origin. We produced a novel proxy for local dengue epidemic activity using a composite index of theoretical climate-driven transmission potential and population density, which we used, along with travel information in a risk flow model, to estimate the importation risks. Findings We find that countries in east Africa face higher risk of importation from Asia, whereas for west African countries, larger risk of importation is estimated from South America. Some countries with high risk of importation experience low local transmission potential which likely hampers the chances that importations lead to local establishment and transmission. Conversely, Mauritius, Uganda, Ivory Coast, Senegal, and Kenya are identified as countries susceptible to dengue introductions during periods of persistent transmission suitability. Interpretation Our work improves the data driven allocation of surveillance resources, in regions of Africa that are at high risk of dengue introductions and establishment. This will be critical in detecting and managing imported cases and can improve local response to dengue outbreaks. Funding Rockefeller Foundation, National Institute of Health, EDCTP3 and Horizon Europe Research and Innovation, World Bank Group, Medical Research Foundation, Wellcome Trust, Google.org, Oxford Martin School Pandemic Genomics programme, John Fell Fund Evidence before this study Despite the significant global burden of dengue virus globally, Africa remains relatively understudied due to limited reporting and diagnostic capabilities. We searched PubMed for articles in English published on and before May 6, 2024, that included “Dengue OR dengue”, “Africa”, and "importation OR imported”. Few studies have investigated the introduction of dengue into African countries. Limited evidence includes phylogeographic studies describing a potential introduction of dengue from Brazil into Angola in 2013 and evidence of multiple historical introductions of dengue from Asia to Africa over several years. Before our study, none had employed a modelling framework to investigate the continental risks of importing dengue via viremic travellers into African countries from other regions of high dengue incidence. Added value of this study This study provides a novel approach to assessing the risk of dengue importation into Africa, integrating temperature-dependent transmission potential and air travel data. By identifying high-risk regions and highlighting the complex interplay between travel patterns, population density, and ecological factors, our findings enhance the understanding of dengue dynamics in Africa. This information enables targeted allocation of surveillance resources, improving preparedness and response to potential dengue outbreaks in susceptible regions. Implications of all the available evidence The integration of transmission potential as local epidemic activity and air travel data into a risk flow metric provides valuable insights into the risk of dengue importation into African airports from high-incidence countries. These findings have implications for tailored surveillance and prevention strategies in high-risk regions, facilitating early detection and management of potential dengue imported cases outbreaks in Africa. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement CERI and KRISP are supported in part by grants from the Rockefeller Foundation (HTH 017), the National Institute of Health USA (U01 AI151698) for the United World Antivirus Research Network (UWARN), and the INFORM Africa project through IHVN (U54 TW012041), European Union supported by the Global Health EDCTP3 Joint Undertaking and its members, European Union Horizon Europe Research and Innovation Programme (101046041), the Health Emergency Preparedness and Response Umbrella Program (HEPR Program), managed by the World Bank Group (TF0B8412), the Medical Research Foundation (MRF-RG-ICCH-2022-100069), and the Wellcome Trust (228186/Z/23/Z). M.U.G.K. acknowledges funding from The Rockefeller Foundation, Google.org, the Oxford Martin School Pandemic Genomics programme, European Union Horizon Europe programme projects MOOD (#874850) (also V.C.) and E4Warning (#101086640), the John Fell Fund, a Branco Weiss Fellowship and Wellcome Trust grants 225288/Z/22/Z, 226052/Z/22/Z & 228186/Z/23/Z, United Kingdom Research and Innovation (#APP8583) and the Medical Research Foundation (MRF-RG-ICCH-2022-100069.). The content and findings reported herein are the sole deduction, view and responsibility of the researcher/s and do not reflect the official position and sentiments of the funding agencies. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes