# Evolution of human leptospirosis in French Guiana, 2016–2022

## TL;DR

This study tracks how leptospirosis, a rodent-borne disease, has changed in French Guiana from 2016 to 2022, showing it's becoming more common and affecting vulnerable populations.

## Contribution

The study provides updated epidemiological data on leptospirosis in French Guiana and identifies shifts in patient demographics and risk factors over time.

## Key findings

- The annual number of leptospirosis cases doubled from 5.8 to 14.0 per 100,000 adults between the two study periods.
- Over a third of patients were in precarious socio-economic conditions, and most had multiple exposure factors including rodent contact.
- Severe cases remained stable, but faster clinical suspicion and demographic shifts like older age and more female patients were observed.

## Abstract

Leptospirosis is a re-emerging zoonotic disease. In French Guiana (FG), updating its epidemiology is essential to guide prevention strategies. This study aimed to describe human leptospirosis cases from 2016 to 2022 and compare them to the cases from 2007 to 2014 (using similar diagnostic criteria).

A multicentric cross-sectional study was conducted in the three hospitals of FG and the remote health centers. Cases were identified via biological diagnostics, defined by a compatible clinical picture and a positive biological test and classified according to the test as confirmed (positive PCR or Microscopic agglutination test [MAT] ≥400) or probable (MAT = 200 or positive IgM only without alternate diagnosis). Severe cases involved renal, circulatory, or respiratory failure, or death. A total of 188 cases were included, of which 138 (73.4%) were confirmed. Median (IQR) age was 38 (28–52) years, with a male-to-female ratio of 3.1. Twenty-six (13.8%) cases were severe, including 4 deaths (2.1%). Most patients had multiple exposure factors with rodent exposure being the most common; 67.5% (available data) had both domestic and non-domestic exposures. Notably, over a third of patients were in a situation of precarity, uninsured or lived in informal settlements. The mean (SD) annual number of cases increased from 5.8 (2.7) per 100,000 of the adult population in the 2007–2014 period to 14.0 (9.2) in the recent study period (p = 0.03). Early clinical suspicion improved, while the proportion of severe cases remained stable.

Leptospirosis is an increasing public health issue in FG which particularly affects socioeconomically vulnerable populations. Routes of transmission appear multiple.

Leptospirosis is a bacterial disease transmitted from animals, especially rodents, that can cause serious illness or death. In French Guiana, many people live in vulnerable conditions, such as informal settlements, with exposure to flooding and diverse animal reservoirs, making it important to update our knowledge of who is affected and how the disease spreads. This study updates the characteristics of patients diagnosed with leptospirosis from 2016 to 2022 and compares them with those from 2007–2014 using a similar and robust case definition. The overall burden of the disease, including severe and non-severe cases, doubled over the study periods. Significant changes included higher comorbidities, more patients born in Haiti, differences in occupation, and faster clinical suspicion. A trend toward older age and a higher proportion of female patients were also observed. Patients often live in precarious conditions and have multiple sources of exposure both at home and elsewhere. The proportion of severe cases remained similar. These findings highlight subtle shifts in the epidemiology of leptospirosis in French Guiana and provide insights to support more targeted public health interventions and the identification of at-risk populations.