The objective of the study is to estimate the incidence of Jarisch-Herxheimer Reactions (JHR) during antibiotic treatment of human leptospirosis cases in New Caledonia.

Participants are patients managed in one of the 5 centres participating in the study, in whom a clinical doctor suspected leptospirosis. The average number of leptospirosis cases in New Caledonia is 89 per year. Given the proportion of positive diagnostic tests (approximately 10%) 900 inclusions are planned for this study.

Patients are included at the time of the consultation during which leptospirosis is suspected, before the initiation of their antibiotic therapy and independently of the clinical form they presented.

Data (socio-demographic and health) and blood samples will be collected at 3 points in the study: at baseline, three hours and six hours after antibiotic treatment.

This study will allow better management of patients with leptospirosis.

The objective of the study is to estimate the incidence of Jarisch-Herxheimer Reactions (JHR) during antibiotic treatment of human leptospirosis cases in New Caledonia.

Secondary objectives of the study are to describe the JHR during leptospirosis (describe clinical, haemodynamic and cytokine response parameters), to describe the effects of the progressive introduction of antibiotic (ATB) for the treatment of leptospirosis and to harmonise management practices for patients with leptospirosis in NC.

Participants are patients managed in one of the 5 centres participating in the study, in whom a clinical doctor suspected leptospirosis. The average number of leptospirosis cases in New Caledonia (NC) is 89 per year. Given the proportion of positive diagnostic tests (approximately 10%) 900 inclusions are planned for this study.

Patients are included at the time of the consultation during which leptospirosis is suspected, before the initiation of their antibiotic therapy and independently of the clinical form they presented.

Blood samples will be collected at 3 points in the study: at baseline, three hours and six hours after antibiotic treatment.

Data will be collected at 4 points in the study: at baseline, three hours, six hours after antibiotic treatment and one day after treatment introduction (last point by phone call).

The data obtained will allow us to describe for the first time, in a prospective study, the JHR associated with leptospirosis in a significant number of patients.

The data obtained will also help to describe the impact of a therapeutic strategy on the evolution of the disease, which has not yet been evaluated. This study also aims to help harmonise the management of patients with leptospirosis in NC.

This study will allow better management of patients with leptospirosis.

Inclusion Criteria:

• Be over 18 years of age (at the time of inclusion);
• Be suspected of developing leptospirosis by the clinician in one of the 5 participating centres
• Have been informed of the use of their samples for non-therapeutic scientific research purposes by a note and information sheet established by the Institut Pasteur of New Caledonia (IPNC) and the Institut Pasteur Paris (IPP), provided and explained by the inclusion centre.
• Have expressed their oral consent to participate in this research project

Non inclusion criteria:

• Under 18 years of age
• Have not given oral consent to participate
• Have a chronic inflammatory disease.
• Having concomitant antibiotic and/or anti-inflammatory treatment or medical management incompatible with the purpose of the study,
• Pregnant or breastfeeding women.

Exclusion Criteria:

- Leptospirosis diagnostic is not confirmed by molecular biology. Complete destruction of the corresponding samples will be ensured. Clinical data and biological analyses will also be removed from the data associated with the research.