Leptospirosis in France: 886 cases in 2024, peak expected in August 2026 — the risk rats pose to your family

On 6 February 2026, Santé publique France published the national 2024 leptospirosis report — the first full year of mandatory notification since the disease was added to the list in August 2023. The figures are clear: 886 cases reported during the year, 441 cases in mainland France and Corsica, 445 cases in the overseas territories (DROM), 13 deaths and a hospitalisation rate of 74%. The disease is severe. And the seasonal pattern is sharp: cases start rising in May, peak in August, and continue through September and October. Right now, as summer 2026 is in full swing and Île-de-France swings between heatwaves and stormy spells — bringing stagnant water, flash floods and overloaded sewer networks — the question is no longer whether leptospirosis is present in France: it is. The real question is why rats are the main reservoir and how to protect yourself as a household member, parent, swimmer, gardener, homeowner or building manager.

What exactly is leptospirosis?

Leptospirosis is a bacterial disease caused by spirochetes of the genus Leptospira. The serogroup Leptospira interrogans serovar Icterohaemorrhagiae is by far the most common in France: it is carried by brown rats (Rattus norvegicus) — the very same rats that thrive in our sewers, cellars, bin rooms and along the banks of our urban waterways. The bacteria is shed in the urine of infected rodents and survives for several weeks in fresh water, mud and damp soil, especially at mild temperatures (15-30 °C).

Humans are infected when a mucous membrane (eye, mouth, nose) or broken skin (wound, scratch, maceration) comes into contact with water or soil contaminated by this urine. The main at-risk activities in mainland France are well known:

• Swimming, canyoning, kayaking, rafting, fishing in fresh water, especially after a flood
• Gardening and DIY outdoors, with contact with mud or contaminated tools
• Occupational exposure: sewer workers, refuse collectors, road crews, farmers, vets, fish farmers
• Living in collective housing infested with rats: cellars, bin rooms, underground car parks
• Travel to the DROM (La Réunion, Mayotte, West Indies), where circulation is intense year-round

Key point: leptospirosis is not an "exotic disease." It is an urban and peri-urban infectious disease, spread by the rat in your cellar or in the gutter of your street.

What the 2024 Santé publique France report says

The national bulletin of 6 February 2026 (PDF Santé publique France) brings together the data from the first full year of mandatory notification. Key figures to remember:

• 886 cases reported in 2024, including 441 in mainland France and Corsica (notification rate 0.67 per 100,000 inhabitants) and 445 in the DROM (La Réunion, Mayotte, Guadeloupe, Martinique, French Guiana).
• 74% hospitalisations, 13 deaths: the disease is not mild. The severe form, called "Weil's disease", combines fulminant jaundice, acute kidney failure and haemorrhages, with a mortality of up to 10-15% without treatment.
• 79% male, median age 49, age groups most affected: 30-50 and 45-65. Men are overrepresented because they accumulate the at-risk activities (DIY, sport, hunting, sewer work).
• Highly seasonal: onset in May, peak in August, tailing off in November. The bacteria thrives in lukewarm water.
• Most affected regions in mainland France: Brittany, Bourgogne-Franche-Comté, Nouvelle-Aquitaine, Pays de la Loire, Auvergne-Rhône-Alpes — all regions where fresh water (lakes, rivers, ponds) is abundant and brown rat populations are dense.
• Reported exposures: swimming in fresh water (29%), gardening (15%), contact with animals (12%), occupational activity (9%), water sports (8%).

Key takeaway: Leptospirosis is not a 19th-century relic. With 886 cases in 2024 and a peak hitting right now (July-August), it is an established public health issue — and the rat is its main vector.

La Réunion on alert: 142 cases in April 2026

The French overseas territories are facing a particularly severe 2026 season. The bulletin of 17 April 2026 from Santé publique France in the Indian Ocean reports, for La Réunion:

• 142 cases recorded by mid-April 2026 — a record for that time of year, already exceeding the previous monthly record of 61 cases (March 2024) from a record year.
• 66 cases reported in March 2026 alone — an unprecedented figure for that month.
• 6 out of 10 cases hospitalised, 28% in critical care / ICU — severity is massive.
• 1 death already recorded at that date.
• Male predominance (89%), age groups 45-59 and 60-74, dominant exposures: agriculture, livestock farming, freshwater leisure activities (heavily practised in La Réunion: rivers, basins, canals).

And La Réunion is not alone: Martinique and Guadeloupe are also under enhanced surveillance. For a resident of Île-de-France planning summer 2026 holidays in the DROM or returning from one, vigilance must be maximum.

Auvergne-Rhône-Alpes: 139 cases between 2023 and 2025

The regional ARA bulletin published 9 June 2026 (PDF Santé publique France ARA) confirms that mainland France is not spared:

• 139 cases reported between August 2023 and December 2025 in Auvergne-Rhône-Alpes.
• 75 cases in 2024 (record year), 34 in 2025.
• Highest notification rate in Savoie (2.21 per 100,000 inhabitants in 2024), followed by Haute-Savoie, Ain and Isère — all mountain and freshwater-sport areas.
• 84% hospitalisations in 2024, including 37% in ICU.
• Several cluster cases documented: canyoning (summers of 2023, 2024, 2025), Vichy-Bellerive triathlon (summer 2024). Every time, the common factor: swimming or immersion in fresh water after rain, in areas with dense rat populations.

What you need to understand: leptospirosis is not only a tropical issue. Rats on riverbanks, in urban parks and in sewer networks silently contaminate the rivers, ponds, lakes and canals where we swim, paddle and walk barefoot.

Close-up of a brown rat, the main reservoir of the Leptospira bacteria in urban and peri-urban areas

Symptoms: from flu-like syndrome to Weil's disease

The incubation is short: 2 to 30 days, most often 7 to 14 days after exposure. Forms range from mild leptospirosis (80-90% of cases) to severe disease (Weil's disease, 5-10% of cases).

Warning signs (mild form)

• Sudden high fever (39-40 °C), chills
• Severe headaches, retro-orbital
• Muscle pain (myalgia), especially in the calves and thighs — very suggestive
• Bilateral conjunctivitis
• Possible skin rash
• Nausea, vomiting, abdominal pain

These signs initially suggest a flu-like syndrome or gastroenteritis, which often delays diagnosis. If you have been exposed to fresh water or rats in the past 2 weeks, tell your doctor: a doxycycline course started early (within 5 days) shortens the disease and reduces the risk of severe forms.

Warning signs of the severe form (Weil's disease)

• Jaundice: yellow skin and eyes
• Acute kidney failure: very dark urine, little or no urine
• Haemorrhages: nosebleeds, bleeding gums, petechiae, haemoptysis
• Neurological disorders: confusion, agitation
• Respiratory distress

Medical emergency: Weil's disease is a life-threatening emergency. At the first signs of jaundice, severe malaise or neurological symptoms after a risk exposure, call 15 (SAMU) without delay.

Why rats are the core of the problem

The transmission chain is built entirely around the brown rat (Rattus norvegicus). Understanding this chain is understanding why deratisation is the primary collective prevention measure.

The rat: an asymptomatic reservoir

The brown rat hosts Leptospira in its kidneys and sheds it continuously in its urine, without being ill itself. A single infected rat contaminates tens of square metres of damp soil, puddles, gutters and manholes. A colony of 20 rats in a sewer network can contaminate an entire street section.

Fresh water: the ideal survival medium

L. Icterohaemorrhagiae survives several weeks in fresh water at 20-25 °C, and several months in mud. Sewer networks are a permanent reservoir, and after a storm or a flood, the contaminated water rises into cellars, car parks, basements, the banks of the Marne and the Seine, and playgrounds.

Humans: accidental hosts

Humans are accidental hosts: they do not transmit the disease. But they pay the price of proximity to rats. And it is precisely this proximity that Pro Deratisation can push back, through targeted professional deratisation of sewer networks, building cellars, bin rooms and building perimeters.

To understand how deratisation acts on the whole chain, also see our guide on why to call a professional deratisation company and our overview of deratisation in summer 2026.

The complete prevention plan

For households: the basics

1. Tackle rats at the source: this means professional deratisation of your cellar, bin room, garage and garden. A rat within 50 metres of your home is already too close.
2. Seal entry points: a rat fits through a hole 1.5 cm wide. Block cracks, pipe passages and air vents with galvanised mesh and mastic.
3. Waste hygiene: closed bins regularly cleaned with a high-pressure jet, never leave bags outside at night, secure composting in the garden.
4. Hermetic storage of all food, both human and animal (kibble, bird seed, livestock feed).
5. Do not overfeed stray animals or birds, especially in summer.
6. Wear gloves for gardening and wash your hands and tools systematically after contact with soil, mud or rainwater.

For swimmers and freshwater sport enthusiasts

• Avoid swimming in turbid fresh water or after a storm (contaminated water takes 24-48 h to settle).
• Do not walk barefoot on muddy banks, especially after a flood.
• Cover any wound (even small) with a waterproof plaster before the activity.
• Wear protective clothing for canyoning, kayaking, rafting, triathlon: wetsuit, boots, gloves.
• Wash and shower immediately after the activity.
• See a doctor if you develop a fever within 2 weeks of exposure, even if the swim seemed harmless.

For travellers to the DROM

• Vaccination is recommended for long stays and at-risk activities (river hiking, canyoning, agriculture, livestock) in La Réunion, Mayotte, New Caledonia. The Spirolept vaccine covers L. Icterohaemorrhagiae (the most common serogroup): 2 injections 15 days apart, booster at 4-6 months, then every 2 years. Ask your doctor or an international vaccination centre at least 2-3 weeks before departure.
• Chemoprophylaxis with doxycycline is possible for short, very high-risk exposures (relief work in flooded areas, professionals).

For exposed professionals

Sewer workers, refuse collectors, road crews, farmers, vets, fish farmers: vaccination is recommended by the Haut Conseil de la santé publique (HCSP). The employer has a duty to assess risks and to provide PPE (boots, gloves, waders, waterproof overalls). In case of cuts or eye splashes, immediate rinsing and medical consultation within 24 hours for antibiotic prophylaxis.

How Pro Deratisation acts on the reservoir

The foundational treatment of leptospirosis is deratisation of the places where rats live, move and urinate. That is exactly our job. Our interventions, in Île-de-France and across France, target:

• Sewer networks and manholes: installation of secured bait stations (Certibiocide), treatment of high-density rat sections.
• Building cellars and underground car parks: diagnosis, sealing, baiting, follow-up.
• Bin rooms and technical shafts: securing, treatment, high-pressure cleaning.
• Building perimeters, schoolyards, nurseries, care homes, restaurants: implementation of an integrated pest management plan (IPM) with monthly follow-up.
• Parks, riverbanks, playgrounds: diagnosis, treatment in coordination with municipal services.

For the legal framework and the obligations of owners and co-ownerships, see our article on mandatory deratisation in co-ownerships and restaurants and for costs, our guide to the price of professional deratisation in 2026. For specific cases of severe infestation, also see rats in buildings when bins are poorly managed and rat bites in a nursery school.

Stagnant water in an urban area, a medium favourable to the survival of the Leptospira bacteria shed by rats

In summary

• Leptospirosis is a severe bacterial disease transmitted by the urine of brown rats, with 886 cases in France in 2024, 13 deaths and an August peak that is happening right now.
• La Réunion is on historic alert (142 cases by April 2026); Auvergne-Rhône-Alpes, Brittany and Pays de la Loire were the most affected mainland regions in 2024-2025.
• The brown rat is the central reservoir: deratising cellars, bin rooms, sewer networks and building surroundings is cutting the chain at source.
• Swimmers, kayakers, gardeners, pet owners, professionals: adopt the barrier gestures (waterproof plasters, protective clothing, washing, vaccination where indicated).
• At the first sign of fever after exposure to fresh water, mud or rats, see a doctor without delay: early antibiotic treatment (doxycycline) can make all the difference.

Pro Deratisation works across the whole of Île-de-France — Paris, Seine-et-Marne, Yvelines, Essonne, Hauts-de-Seine, Seine-Saint-Denis, Val-de-Marne, Val-d'Oise — as well as in Oise and neighbouring departments, providing diagnosis, deratisation, follow-up and advice to households, co-ownerships, businesses, restaurants, schools, nurseries, care homes and local authorities. If you suspect the presence of rats in your environment, don't let the bacteria settle in: contact us for a free diagnosis.

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