The first reported Crimean-Congo hemorrhagic fever reinfection in the literature: 11 years apart.

Crimean-Congo Hemorrhagic Fever (CCHF) is a viral zoonosis endemic to several regions, including Türkiye. Although it is generally assumed that CCHFV infection confers long-lasting immunity, the durability and mechanisms of this protection remain unclear. Here, we report the first PCR-confirmed reinfection case of CCHFV, occurring 11 years after the initial episode, in a patient from the hyperendemic region of Sivas, Turkiye. The second episode presented with milder symptoms and no hemorrhagic findings, suggesting a degree of partial immune protection. This case challenges existing assumptions about lifelong immunity to CCHFV and highlights the need for further studies on reinfection dynamics and immune memory in endemic settings.