Waterborne diseases are illnesses spread through water contaminated with faeces or other pollutants. The World Health Organization links contaminated water and poor sanitation to cholera, diarrhoea, dysentery, hepatitis A, typhoid and polio, and estimates that contaminated drinking water causes about 505,000 diarrhoeal deaths each year. They are prevented by a protected water source, safe storage and treatment at home, sanitation that keeps waste away from water, and handwashing.
What makes water dangerous
Water itself isn’t the problem. What’s in it is. When human or animal waste reaches a water source — through open defecation, a nearby latrine, flooding or runoff — the bacteria, viruses and parasites inside it can make people sick. The WHO estimates that at least 1.7 billion people use a drinking-water source contaminated with faeces.
Diseases linked to contaminated water
The World Health Organization links contaminated water and poor sanitation to the transmission of:
Diarrhoea
The most common. Contaminated drinking water is estimated to cause about 505,000 diarrhoeal deaths a year.
Cholera
A severe intestinal infection that can spread rapidly where water and sanitation break down.
Dysentery
Intestinal infection causing bloody diarrhoea, often spread through contaminated water and food.
Typhoid
A bacterial infection spread through food and water contaminated with faeces.
Hepatitis A
A viral liver infection, commonly spread where clean water and sanitation are lacking.
Polio
A virus that can spread through contaminated water, which is why sanitation matters for eradication.
This is general health education, not medical advice. Anyone with severe or persistent symptoms should seek medical care.
Who is most at risk
Young children are the most vulnerable, because diarrhoea dehydrates small bodies quickly. Families that drink untreated surface water — about 106 million people in 2024, according to the JMP — face the highest risk. Health facilities without reliable water also put patients and staff at greater risk of infection.
How waterborne diseases are prevented
- A protected source. A well-built borehole with a sanitary seal and apron keeps surface contamination out. See how a community well is built.
- Safe storage. Clean, covered containers stop water being re-contaminated between the pump and the cup.
- Household treatment where needed. The WHO promotes household water treatment and safe storage — such as boiling, chlorination and filtration — where water may be unsafe.
- Sanitation. Latrines sited safely away from water sources keep waste out.
- Handwashing. Soap and water at the right moments break the chain of infection.
Why a well is a health intervention
A protected community water point does more than shorten the walk. It replaces the river, the pond or the unprotected spring as the place families drink from. Combined with sanitation and hygiene, it is one of the most effective ways to stop these diseases at the source.
“I was thirsty, and ye gave me drink.”
Matthew 25:35
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Questions people ask
What diseases are caused by contaminated water?
The World Health Organization links contaminated water and poor sanitation to cholera, diarrhoea, dysentery, hepatitis A, typhoid and polio.
How many people die from unsafe drinking water?
The WHO estimates that contaminated drinking water causes about 505,000 diarrhoeal deaths each year.
How can waterborne diseases be prevented?
Use a protected water source, store water in clean covered containers, treat water at home by boiling, chlorination or filtration when it may be unsafe, keep sanitation away from water sources, and wash hands with soap.
Does a water well prevent disease?
A properly built and maintained well with a sanitary seal protects water from surface contamination and can replace unsafe sources such as rivers and ponds. It works best alongside sanitation, safe storage and handwashing.
New to a term? See the water & wells glossary ↗
Sources
- World Health Organization — Drinking-water fact sheet (September 2023) ↗
- World Health Organization — Household water treatment and safe storage ↗
- UNICEF & WHO — Fast facts: 1 in 4 people globally still lack access to safe drinking water (August 2025) ↗
- WHO/UNICEF Joint Monitoring Programme — Progress on household drinking water, sanitation and hygiene 2000–2024 (2025) ↗