Floods and your health: leptospirosis, diarrhoea and other risks during the monsoon

The monsoon season has begun

MetMalaysia says the 2026/27 Northeast Monsoon began on 27 October 2026 and will last until March 2027. It expects 3 to 5 episodes of continuous heavy rain between November and January, followed by drier weather from January.

Floods have already started. On 25 October, heavy rain caused flash floods at 10 locations on Penang island, and a 73-year-old resident died in a landslide in Paya Terubong. In Kedah, 202 people from 69 families were in relief centres in Yan on 27 October, and the state has listed 90 flood hotspots. On 28 October, five relief centres were open nationwide, in Kedah and Selangor.

Check river levels on the Department of Irrigation and Drainage’s Public Infobanjir site, and follow MetMalaysia’s weather warnings.

Illnesses to watch for during and after floods

The Ministry of Health and the National Security Council list these as the main flood-related diseases:

• Diarrhoea and food poisoning, including dysentery and, rarely, cholera
• Hepatitis A and E, from contaminated water and food
• Leptospirosis, from water or mud contaminated with animal urine
• Chest infections and flu, which spread easily in crowded relief centres
• Skin infections and eye infections (conjunctivitis)
• Dengue and other mosquito-borne diseases, after the water recedes

In practice, most people who fall ill in relief centres have chest and skin infections. During the November 2025 floods, health teams treated 2,083 people in relief centres. The most common problems were respiratory infections (376 cases) and skin infections (92), with 15 cases of gastroenteritis. In the larger November–December 2024 floods, there were 6,730 respiratory infections, 3,021 skin infections and 298 cases of gastroenteritis. No outbreaks were declared in either year.

Leptospirosis: the flood fever to know about

Leptospirosis, often called kencing tikus (rat urine disease), is caused by bacteria in the urine of rats and other animals. The bacteria survive for weeks in water and wet soil, and enter the body through cuts, scratches, the eyes, nose or mouth. Wading or cleaning up in floodwater is a common way to catch it. It has been a notifiable disease in Malaysia since 2010.

Symptoms usually start 5 to 14 days after exposure, but can appear anywhere from 2 to 30 days:

• Sudden fever, chills and headache
• Muscle aches
• Red eyes
• Vomiting, diarrhoea, or a rash

Most cases are mild, but some people develop a severe form with yellow skin and eyes (jaundice), kidney failure or bleeding in the lungs, which can be fatal.

Melioidosis: a risk for people with diabetes

Melioidosis is a less well-known infection caused by bacteria that live in soil and muddy water. Cases rise after heavy rain and floods. It mostly affects people with diabetes, kidney or liver disease, or thalassaemia. In one Pahang study, about three-quarters of patients had diabetes. Symptoms, which can start 1 to 3 weeks after exposure, include fever, cough, chest pain or abscesses. It needs weeks of hospital antibiotics, so see a doctor early for any fever after a flood if you have diabetes.

Safe water and food

• Drink boiled or bottled water until the authorities say tap water is safe. Bring water to a rolling boil for 1 minute. If it is cloudy, let it settle and filter it through a clean cloth first.
• Throw away any food that touched floodwater, including packaged food that isn’t in a sealed can, and food from a fridge that lost power for a long time.
• Don’t wash food, dishes or yourself in floodwater.
• Wash your hands with soap and clean water before eating and after cleaning up.
• For diarrhoea, drink oral rehydration salts (ORS) and plenty of clean fluids. See a doctor for blood in the stool, high fever, or signs of dehydration, especially in children and older people.

Cuts, wounds and tetanus

• Wear boots and gloves in floodwater and mud, and avoid wading where you can.
• Cover cuts with waterproof plasters before going into water.
• If you get a cut, wash it well with clean water and soap, and keep it clean and dry.
• Flood wounds count as dirty wounds. See a doctor for a tetanus booster if your last one was 5 or more years ago, or if you aren’t sure.
• See a doctor if a wound becomes red, swollen, hot or painful, or leaks pus.

Cleaning up safely

• Turn off electricity at the main switch before entering a flooded home if you can do so safely, and have wet electrical items checked before use.
• Never run a generator indoors, in a garage or near windows. Keep it at least 6 metres from doors, windows and vents. Generators produce carbon monoxide, which can kill without warning.
• Protect yourself with boots, gloves, goggles and, if there is mould, an N95 mask. Open windows while you clean.
• Remove mud first, then wash hard surfaces with soap and water and disinfect them with diluted bleach: no more than 1 cup (about 240 ml) of household bleach in about 4.5 litres of water.
• Never mix bleach with ammonia or other cleaners. It makes a toxic gas.
• Throw away soaked mattresses, carpets and soft items that can’t be dried within 24 to 48 hours, as mould grows quickly.

Dengue after the floods

As floodwater recedes, it leaves puddles, blocked drains and water-filled containers where Aedes mosquitoes breed. Dengue cases in Malaysia have already passed 78,000 this year. After a flood, walk around your home and empty anything holding water, and use mosquito repellent. See our guide to dengue warning signs.

Looking after your mind

Losing belongings, being displaced or worrying about the next flood is stressful. Trouble sleeping, irritability and anxiety are common afterwards, and children may become clingy or upset. Talk to someone you trust, keep to routines where you can, and ask for help if it doesn’t ease. The Ministry of Health’s Talian HEAL 15555 offers free psychosocial support.

Useful contacts

Where to see a doctor after a flood

See a GP for a fever, diarrhoea, skin infection or wound after contact with floodwater, and mention the flood. Our directory lists GP clinics across Kuala Lumpur, Selangor, Penang, Perak and other states, including clinics open late and at weekends.

Browse the clinic directory

Frequently asked questions