Recurrent borreliosis (RB) is a bacterial infection transmitted by ticks or lice. These infections occur in both temperate and tropical regions, but are rare in Australia and Antarctica. Due to climate change, the areas inhabited by the vectors of these infections are shifting, and the number of at-risk regions has significantly increased in recent years. More than twenty RB species have been described, responsible for variable clinical manifestations including fever, myalgia, digestive disorders, and sometimes neurological symptoms. Tick-borne RB represents a major public health problem, particularly in Africa. Mortality from these infections ranges from 5% to 10%. In recent years, diagnostic techniques have evolved. Microscopic diagnosis was initially the gold standard but had only moderate sensitivity and exhibited inter-operator variability. The advent of molecular biology now allows for increased sensitivity with excellent specificity and also enables the identification of the causative species.

A few cases have been described in France, consisting mainly of case reports. Therefore, this study will provide a comparative description, within a series, of cases diagnosed in France: symptoms, patients' countries of origin, Borrelia species, diagnostic techniques, management, and patient outcomes.

Inclusion Criteria:

• Minor or adult subject
• Having presented (from January 1, 2013, to January 1, 2025) with recurrent imported borreliosis, the diagnosis of which was confirmed by the CNR Borrelia in Strasbourg

Exclusion Criteria:

- Refusal to participate in the study

Minor or adult subject having presented (from January 1, 2013, to January 1, 2025) with recurrent imported borreliosis, the diagnosis of which was confirmed by the CNR Borrelia in Strasbourg