Serological signals of past dengue exposure in general practice in southern mainland France

The incidence of autochthonous arboviral infections in mainland France, particularly in the southern region of Occitanie, is increasing. Despite mandatory reporting, non-specific symptoms and asymptomatic cases likely lead to case underestimation. This study aimed to assess dengue seroprevalence for the first time in the general population consulting in routine general practice in southern mainland France. We conducted a multicenter cross-sectional seroepidemiologic survey in the adult population consulting in routine care in three departments (Hérault, Gard, Pyrénées-Orientales) of Occitanie. Patients completed a brief questionnaire, and two capillary blood drops were collected on filter paper. Multiplex serology (Luminex®) was used to detect IgG antibodies against the four DENV serotypes. A total of 629 participants were enrolled between March and May 2024, with a median age of 54 years, of whom 67 % were female. Nine patients tested positive for anti-DENV IgG, yielding an overall prevalence of 1.43 % (95 %CI: 0.75-2.69), including two participants with no travel history. These findings, although they should be interpreted with caution due to the potential for false positives and cross-reactivity, highlight the possibility of low-level dengue circulation in southern France escaping the surveillance system. This pilot study highlights the need to enhance the arboviral surveillance networks in response to the increasing arboviral threat in France.