Rickettsia2024 is a multicenter, tissue observational, retrospective and prospective cohort study. Enrollment will take place within the outpatient clinics of the Infectious Diseases and Dermatology Unit of the IRCCS AOUBO and, following an infectious disease consultation in the Bologna Metropolitan area, at the Hospitals and CAUs of the Bologna Local Health Authority. Within these UUOOs, biopsy samples from normal clinical practice are performed on patients with strong clinical suspicion of Rickettsia infection: therefore, it will not be necessary to perform any additional samples for the conduct of this study. Samples from the normal diagnostic process are sent to the Microbiology UOC, where they are subjected to various analyses. RT-PCR analyses (commercial or in-house kit) and assay of species-specific IgG antibodies will be performed according to clinical practice. Additional tests will be performed with a commercial kit for retrospective samples and with a home-made method for prospective samples.