Bangkok Floods 2026: 7 Health Risks to Watch During and After the Water

Heavy rain and flooding can disrupt daily life very quickly. But even after the water begins to recede, there is another issue worth paying attention to: your health.

Floodwater can carry bacteria, sewage, chemicals and debris. It can also leave behind standing water where mosquitoes breed. Some flood-related illnesses appear within a few days, while others may take several weeks to cause symptoms.

If you have walked through floodwater, cleaned a flooded home, or had contact with contaminated mud or water, knowing what to watch for can help you respond early.

Why can floods make people sick?

During a flood, the most immediate dangers are usually drowning, injuries and electrical hazards. Once the water starts going down, the health risks change.

Contaminated water, damaged sanitation systems, mosquitoes, rodents and prolonged contact with wet environments can increase the risk of infections and other health problems.

This does not mean that every flood will cause a disease outbreak. The level of risk depends greatly on local sanitation, access to clean water and how much contact people have with floodwater.

1. Leptospirosis: one of the main infections to watch for

Leptospirosis is closely associated with flooding in Thailand. The bacteria that cause the disease can be carried in the urine of rats and other animals and spread through contaminated water or mud.

The bacteria may enter the body through cuts and scratches, through the eyes, nose or mouth, or even through skin that has been immersed in water for a long time.

Symptoms do not always appear immediately. They may develop several days or even weeks after exposure.

Watch for:

• Sudden fever
• Headache
• Muscle pain, particularly in the calves
• Red eyes
• Unusual tiredness

If you develop a fever after walking through floodwater, tell your doctor about the exposure. It is an important clue when deciding which tests may be needed.

For more information, see the ArokaGO Health Library guide to leptospirosis.

2. Melioidosis: especially important for people with diabetes

Melioidosis is caused by bacteria naturally found in soil and surface water in Thailand. Heavy rain can bring people into closer contact with contaminated soil and muddy water.

The bacteria may enter through broken skin, contaminated water or, in some situations, through inhalation.

Most people will not develop melioidosis simply from being exposed to rain or mud. However, the disease can become serious, particularly in people with underlying health conditions.

People with diabetes, kidney disease or weakened immunity should be especially careful about walking barefoot or exposing open wounds to floodwater and mud.

Seek medical attention if you develop an unexplained fever, cough, breathing problems or a skin infection after significant exposure to muddy water.

For more information, see the ArokaGO Health Library guide to Melioidosis.

3. Dengue can become a problem after the flood

Dengue is not transmitted through floodwater. The problem often comes afterwards.

Once the rain stops, water may remain trapped in buckets, plant pots, tyres, drains, discarded containers and other small spaces. These can become breeding sites for Aedes mosquitoes, which transmit dengue.

After the flood:

• Empty containers that hold standing water
• Keep water storage containers covered 
• Use mosquito repellent
• Wear clothing that reduces mosquito bites where practical

If you develop a fever and dengue is possible, avoid aspirin and ibuprofen unless a healthcare professional advises otherwise. Paracetamol is generally used for fever while dengue is being evaluated.

For more information, see the ArokaGO Health Library guide to Dengue

4. Diarrhoea and contaminated food or drinking water

Flooding can overwhelm drainage and sewage systems. It may also contaminate wells, water pipes, kitchens and food storage areas.

This increases the risk of illnesses linked to contaminated food and water, including food poisoning, typhoid fever, cholera and hepatitis A.

A simple rule after a flood is: when in doubt, do not eat it.

Throw away food that has come into contact with floodwater, particularly food in packaging that is not completely sealed. Drink bottled, boiled or otherwise confirmed safe water until the local supply is considered safe.

If diarrhoea develops, preventing dehydration is the priority. Oral rehydration solution can help replace lost water and salts.

See a doctor if diarrhoea is accompanied by blood in the stool, high fever, severe weakness or signs of dehydration.

5. Do not ignore your feet, cuts and skin

Spending hours walking or standing in dirty water can soften the skin, particularly on the feet. Small cracks and cuts can then become easy entry points for bacteria.

Floodwater can also contribute to skin irritation, wound infections and eye infections.

After contact with floodwater:

• Wash your skin with soap and clean water
• Dry your feet carefully
• Change into clean, dry socks and shoes
• Clean cuts and scratches promptly
• Keep wounds covered when possible

A wound that becomes increasingly red, swollen, warm or painful should be checked by a healthcare professional, particularly if you also develop a fever.

If you received a deep or contaminated wound during the flood, ask your doctor whether your tetanus vaccination is up to date.

6. The biggest danger may not be an infection

Some of the most serious flood-related risks are physical rather than infectious.

Never walk or drive through fast-moving water. Water can hide open drains, damaged roads, sharp objects and electrical hazards.

Be particularly careful when returning to a flooded building. If electricity has not been safely isolated, avoid touching electrical equipment while standing in water or while your hands are wet.

Generators and petrol-powered pumps also create another danger: carbon monoxide poisoning.

Generators should always be operated outdoors and well away from doors, windows and enclosed areas.

7. Floods can affect mental health too

Flooding is not only physically exhausting. Losing belongings, cleaning damaged homes, dealing with disrupted work and worrying about money or family members can take a psychological toll.

Difficulty sleeping, anxiety and feeling overwhelmed can occur after a disaster.

For many people these feelings gradually improve as life returns to normal. But if anxiety, low mood or sleep problems continue for several weeks or begin interfering with daily life, consider talking to a doctor or mental health professional.

When should you see a doctor after a flood?

Pay particular attention to your health during the weeks after exposure to floodwater or mud.

See a doctor promptly if you develop a fever, especially when accompanied by:

• Severe muscle pain
• Red eyes
• Cough or difficulty breathing
• Yellowing of the skin or eyes
• An infected wound
• Persistent diarrhoea or vomiting

Seek urgent medical care for severe breathing difficulty, confusion, very little urine, unusual bleeding or severe abdominal pain.

Most importantly, tell the doctor that you recently had contact with floodwater or mud. Several flood-related illnesses can look similar in their early stages, and knowing about the exposure can help guide diagnosis.

Frequently asked questions

What diseases can you get from floodwater in Thailand?
Important conditions to be aware of include leptospirosis, melioidosis, diarrhoeal illnesses and skin or wound infections. Flooding can also indirectly increase mosquito breeding and therefore the risk of dengue.

How long after a flood can symptoms appear?
It depends on the illness. Some symptoms may appear within days, while conditions such as leptospirosis may develop several weeks after exposure. Continue paying attention to fever or unusual symptoms even after the water has disappeared.

Should I walk through floodwater if I wear boots?
Waterproof boots and gloves reduce skin contact but do not remove all risk. Avoid entering floodwater unless necessary, particularly if the water is moving quickly or electrical hazards may be present.

What should I do after walking through floodwater?
Wash exposed skin with soap and clean water, dry your feet, clean any wounds and change into dry clothing. Seek medical advice if you later develop fever or signs of infection.

How can I make my home safer after the water recedes?
Remove standing water, throw away contaminated food, clean and dry flooded areas, use safe drinking water and check for electrical hazards before using appliances or entering badly affected areas.

The water may be gone, but keep watching your health

When roads reopen and the water disappears, it is easy to feel that the emergency is over.

For most people, the next step is simply to stay aware.

Think back to whether you had direct contact with floodwater or mud. Check cuts and wounds. Remove standing water around your home. Use safe drinking water. And if you develop a fever or unusual symptoms in the following days or weeks, do not ignore them.

A little awareness after a flood can make it much easier to recognise a problem early.

For more information about one of Thailand's most important flood-related infections, read the ArokaGO Health Library guide to leptospirosis.

If you need medical care, you can also find hospitals and clinics across Thailand on ArokaGO.

References

1. World Health Organization. Flooding and communicable diseases: risk assessment and preventive measures.
2. World Health Organization Regional Office for Europe. Floods and health: guidance for health professionals.
3. Centers for Disease Control and Prevention. About leptospirosis.
4. Naing C, Reid SA, Aye SN, Htet NH, Ambu S. Risk factors for human leptospirosis following flooding: a meta-analysis of observational studies. PLoS One. 2019;14(5):e0217643.
5. Limmathurotsakul D, Wongratanacheewin S, Teerawattanasook N, et al. Increasing incidence of human melioidosis in northeast Thailand. Am J Trop Med Hyg. 2010;82(6):1113–1117.
6. ArokaGO Health Library. Leptospirosis: symptoms and diagnosis.

This article is for educational purposes only and does not replace advice from a qualified healthcare professional. If you develop a fever or other concerning symptoms after contact with floodwater, seek medical care promptly.