5 rainy-season illnesses: how to spot them and how far you can prevent them
Dengue, flu, diarrhoea and food poisoning, leptospirosis and skin infections: the symptoms to watch for and how to prevent them in the rainy season.
Once the rain sets in for days at a time, the symptoms walking into the clinic change, and it's not just colds. Standing water and humidity make many germs spread more easily, from Aedes mosquitoes laying eggs in still water to bacteria carried in floodwater.
Key takeaways
- Standing water around the home breeds Aedes mosquitoes. Empty and cover containers every week.
- A high fever with severe muscle pain after wading through floodwater should raise the possibility of leptospirosis; see a doctor promptly.
- Most diarrhoea is managed by replacing fluids and salts, not with anti-diarrhoeal medication.
- A yearly flu vaccine reduces severity in at-risk groups.
1. Dengue
Caused by the dengue virus and carried by Aedes mosquitoes, which lay eggs in clean still water such as plant-pot saucers, old tyres and uncovered water containers, so the rainy season is the epidemic season.
The classic signs are a persistent high fever, headache and body aches, sometimes with red spots. The phase when the fever falls needs the closest watching, and NSAID painkillers should be avoided.
2. Influenza
It starts like a cold, which lulls people, but usually comes on faster and harder, with high fever, marked body aches and obvious exhaustion, and can lead to complications such as pneumonia in at-risk groups.
A yearly flu vaccine is prevention you can do in advance, especially for young children, older adults, pregnant women and people with chronic conditions.
3. Diarrhoea and food poisoning
- Avoid leftovers and food left out for long in humid weather
- Drink clean water, eat freshly cooked food and wash hands before every meal
- If you have diarrhoea, sip oral rehydration solution to replace lost fluids and salts
- See a doctor for blood or mucus in stool, high fever, vomiting so much you can't eat, or signs of dehydration
4. Leptospirosis
Spread by contact with water or soil contaminated with the urine of carrier animals. The bacteria enter through wounds, grazes or mucous membranes, so people wading through floodwater or working outdoors are at higher risk.
It usually begins with a sudden high fever, chills, headache, severe muscle pain, red eyes and nausea or vomiting. Untreated, it can progress to kidney damage, liver failure or meningitis.
Good to know: If you develop a fever within two weeks of wading through floodwater, tell the doctor you did. It matters for the diagnosis.
5. Skin infections and fungal rashes
- Dry your body and feet thoroughly every time you get wet in the rain or wade through water
- Change wet socks and shoes; don't keep them on all day
- Watch for damp areas between the toes, in the groin and under the breasts
- If you have an open wound, clean and cover it before wading through water
Frequently asked questions
Symptoms alone rarely tell them apart, as many start with fever. Give the doctor the full story (floodwater contact, mosquitoes, what you ate) so the right tests can be chosen.
Related services
Sources
- Influenza (Seasonal) World Health Organization
- Leptospirosis MedlinePlus Medical Encyclopedia, U.S. National Library of Medicine
- About Leptospirosis Centers for Disease Control and Prevention
This content is general information and does not replace an examination, diagnosis or personal advice from a doctor. Published 6 August 2026
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