From structure to immunity: how skin shapes age-related vulnerability to Chikungunya virus infections

Arboviral diseases are resurging globally, with Chikungunya virus (CHIKV) demonstrating a troubling capacity for large-scale outbreaks. In 2024, CHIKV re-emerged in Réunion Island with 47 500 cases and 12 deaths reported by May 2025. Notably, infants and the elderly were disproportionately affected, two age groups with distinct and underexplored vulnerabilities in immune defense, particularly at the skin. As the skin is the primary site of CHIKV inoculation and a key immunological barrier, age-dependent changes in the skin likely influence infection outcomes. Yet, it remains an overlooked target for intervention. This review explores how developmental and aging-associated alterations in the skin's structure, immune composition, and the microbiome shape arboviral pathogenesis, with a particular emphasis on CHIKV, and guides research toward age-tailored interventions for vulnerable populations.