Leptospirosis is a worldwide zoonotic disease, caused by Leptospira spp, whose incidence has been constantly increasing over the past decades. French Guiana (FG) is a French overseas department located in South America, covered mainly by Amazonian forest. The last update of leptospirosis epidemiology in FG dates back to 2014. The aim of this retrospective study was to provide an actualization of human leptospirosis epidemiology in FG.

We conducted a multicentric, cross-sectional study in the three main hospitals of French Guiana (Cayenne and Kourou). Cases of leptospirosis from 2016 to 2022 were retrospectively identified via a systematic screening of all positive serology and polymerase chain reaction (PCR) results. Cases were classified as confirmed, probable based on serology titers and PCR results. Cases with differential diagnosis for cases with positive IgM only were excluded. Infecting serogroups were determined by microscopic agglutination test (MAT) or sequencing of the PCR products. Medical files were reviewed to extract epidemiological data in standardized form. Preliminary results of 2 hospitals (Cayenne and Kourou) are presented here.

On the study period 177 cases were identified, 129 (73%) confirmed and 48 (27%) probable. The incidence increased from 2.4/100,000 in 2016 to 10.4/100,000 in 2022, way higher than the incidence reported by the French National Reference Center on leptospirosis in 2014 which was 0.6/100,000. Median age was 38 (IQR 29-53) years, the male/female ratio was 3.1. The most frequent country of birth was Haïti (n=48/159, 30.2%). Thirty three cases (33/87, 37.9%) declared living in informal settlements. Diagnosis was suspected upon admission for 56,1% of the patients. All subjects reported at least one exposure: mainly rodent proximity (n=69/104, 66.4%) followed by fresh water exposure (n=68/77, 88.3%). One hundred and forty (79.1%) patients were hospitalized, among them 28 (20%) in intensive care unit. Among the whole population 26 cases (14,7%) were classified as severe: 14 (7.91%) underwent extra renal epuration, 8 (4.52%) oro-tracheal intubation, 21 (11.86%) received amines and 4 (2,26%) died. The predominant serogroups were Icterohaemorragiae (n=28/55, 50.9%), Canicola (n=8/55, 14.5%). Leptospirosis cases managed during exceptional rainy years of 2021 and 2022 tended to affect more precarious populations based on housing type and health insurance (not significant). Compared to the 2007-2014 period, patients were older, with a smaller male/female ratio and had more comorbidities, severe forms and lethality rate were similar, initial diagnosis was more frequent and biological diagnosis was mainly made by blood PCR, urine PCR being scarcely prescribed.

Although leptospirosis incidence has increased drastically in the last ten years, clinical and outcome patients’ characteristics, especially severe forms rate, remained stable. However this study revealed changes in the sociodemographic characteristics suggesting that leptospirosis may particularly affect migrant populations from informal settlements or living in precarious conditions. Other studies conducted in these locations and populations as well as in animal and environmental reservoirs would be interesting to complete this data.