In short. Leptospirosis is caused by the Leptospira bacterium, which reaches people in the urine of animals, most often rats, through flood water and mud: through cuts and grazes, the eyes, nose and mouth. On 17 December 2025 the Ministry of Health issued a circular on readiness for outbreaks after floods. Symptoms appear after two days to four weeks: high fever, headache, muscle pain, especially in the calves, red eyes, nausea. If in the past two weeks you walked through a flooded street, cleared a house after a downpour or swam in a river, and a fever with calf pain has set in, see a doctor at once. Protection: closed shoes or boots on a flooded street, gloves when cleaning, a plaster on cuts, and no swimming in muddy water after downpours.
What this disease is. Leptospirosis is caused by the Leptospira bacterium. The disease passes to people from animals, most often from rats, through their urine, writes the Indonesian health ministry. Cows, dogs, pigs, goats and horses can also be carriers: in the animals themselves the bacterium can sit in the kidneys for years without any signs. The ministry's article says that leptospirosis remains a notable problem for Indonesia, especially in places that have floods.
Why this is a rainy season topic. On 17 December 2025 the health ministry issued a circular on readiness for leptospirosis outbreaks after floods. The causes it names are dirt and poor drainage, standing water and a rise in the number of rats after a flood. Separately the ministry mentions cleaning a house and working on flooded plots without protection. In Bali the rainy season, by the BMKG forecast, comes to the mountains in late November and to the south in December, in detail in the guide on the rainy season. A street flooded after a downpour is exactly where the bacterium meets people.
How people get infected. According to the leaflet of the ministry's laboratory service the bacterium goes through the skin, especially through cuts and grazes, even very small ones, and also through the eyes, nose and mouth. The source is animal urine directly, water or soil it has got into, and food spoiled by rats. The ministry lists risk situations in the two weeks before the illness: contact with flood water or rat urine, swimming, washing or working in a river or lake, working barefoot in a rice field or plantation, close contact with sick animals, work as a rescuer, a vet, at a slaughterhouse, and hiking in the mountains.
Symptoms. The first signs appear after two days to four weeks from infection. These are a high fever, headache, muscle pain, especially in the calves, red eyes, nausea, vomiting, diarrhoea, stomach pain, loss of appetite and sometimes a rash. It can also be without any symptoms at all. The ministry warns that the disease is often missed: at the start it is mild and looks like an ordinary cold with a fever. The dangerous signs at which the ministry already suspects a severe course are jaundice, bleeding, shortness of breath, coughing blood, little or no urine, and heart rhythm disturbances. Without treatment leptospirosis damages the kidneys, liver and lungs and can end in death.
When to see a doctor. If in the past two weeks you walked through a flooded street, cleared a house after a downpour, swam in a river or waterfall, and you have developed a fever with muscle pain and red eyes, the ministry asks you to go to a clinic at once and not wait until it gets worse. Tell the doctor plainly that there was contact with flood water: by the ministry's guidance this is a reason to test for leptospirosis first. According to the ministry, the disease is comparatively easy to treat with antibiotics if it is found early, and late diagnosis is what makes it dangerous. Medicines are prescribed only by a doctor. If a high fever persists, it is also worth testing for dengue, with a separate guide. Where to go and how to call an ambulance is in the list of hospitals and emergency numbers.
How to protect yourself. The ministry's advice is simple. On a flooded street and through puddles, walk in closed shoes or rubber boots, because flip-flops are weak protection. Before cleaning after a flood, put on gloves and boots. Cover a fresh cut with a waterproof plaster before going into a river, mud or water after a downpour. Do not swim in the muddy water of rivers and streams after rain. Drink only bottled or boiled water. Wash your hands before eating and after contact with animals. Keep food covered, and do not leave food and rubbish that rats will come for. It is worth having a dog at the villa vaccinated at a vet: there is a leptospirosis vaccine for animals.
What this means for you. In the rainy season leptospirosis is passed on in Bali through flood water. Closed shoes, a plaster on a cut and gloves when cleaning remove most of the risk. A fever, aching calves and red eyes within two weeks of such water are a reason to see a doctor the same day and mention the contact with flood water. The earlier treatment starts, the milder the illness.