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Water glossary

Understanding and Preventing Waterborne Diseases

Explore the causes, transmission, global impact, and crucial prevention strategies for waterborne diseases. Learn about key pathogens and effective water treatment solutions.

General Information on Waterborne Diseases

Waterborne diseases are illnesses caused by the consumption of drinking water contaminated with pathogenic microorganisms, often originating from human or animal faeces. These pathogens can include bacteria, viruses, protozoa, and parasites. The overall understanding of water-associated health issues is complex, with new water-related infectious diseases emerging and known ones re-emerging globally.

While data are robust for some water, sanitation, and hygiene-related diseases (e.g., salmonellosis, cholera, shigellosis), the impact of others, such as malaria, schistosomiasis, or more modern infections like legionellosis or SARS-CoV-2, is still being fully analyzed in relation to water determinants. Even when water plays a critical role in the ecology of a disease, accurately pinpointing the relative importance of aquatic components within local ecosystems can be challenging.

Common Water-Related Diseases

A wide array of diseases can be transmitted via contaminated water:

Dimension of the Problem

Waterborne diseases represent a significant global health burden, particularly in developing countries. Four-fifths (80%) of all illnesses in these regions are attributed to waterborne diseases, with diarrhoea being the leading cause of childhood death.

Globally, approximately 1.1 billion people still lack access to improved drinking water sources, and around 2.4 billion people lack adequate sanitation. Water, sanitation, and hygiene (WASH)-related diseases are responsible for an estimated 2,213,000 deaths annually and an annual loss of 82,196,000 Disability Adjusted Life Years (DALYs), as reported by R. Bos in December 2004.

Specific examples highlight the scale of this issue:

  • Parasitic Infections: The World Health Organization (WHO) estimates that over 2 billion people worldwide are infected with schistosomes and soil-transmitted helminths, with 300 million suffering serious illness as a result.
  • Malaria: Over 1 million people die from malaria each year, a large percentage of whom are children under five, primarily in sub-Saharan Africa. In 2001, malaria accounted for 42.3 million DALYs, representing 10% of Africa's total disease burden. It causes at least 396.8 million cases of acute illness annually. Pregnant women are a primary adult risk group. Malaria has been cited as a factor reducing economic growth in African countries by 1.3% annually over the past three decades.
  • Schistosomiasis: An estimated 246.7 million people worldwide are infected with schistosomiasis, with 20 million experiencing severe consequences and 120 million suffering milder symptoms. Approximately 80% of transmission occurs in sub-Saharan Africa.
  • Diarrhoea: This common waterborne illness causes 4% of all deaths globally and 5% of the total health loss due to disability.
  • Arsenic Contamination: In Bangladesh alone, an estimated 35 million people are exposed daily to elevated levels of arsenic in their drinking water, threatening their health and reducing life expectancy.
  • Post-Disaster Risks: Events like the 2004 Asian tsunami highlighted the increased threat of waterborne diseases following flooding, including Shigellosis, Cholera, Hepatitis A, Leptospirosis, Typhoid Fever, Malaria, and Dengue fever.

Transmission Pathways

Waterborne diseases primarily spread through the contamination of drinking water systems with the urine and faeces of infected humans or animals. This is particularly prevalent when public and private drinking water sources, such as surface waters (rain, creeks, rivers, lakes), become contaminated. Runoff from landfills, septic fields, sewer pipes, or residential/industrial developments can also introduce pathogens into surface water bodies.

This contamination leads to faecal-oral diseases like cholera and typhoid. However, faecal material can also reach the mouth through other routes, such as contaminated hands or food. Contaminated food is often the most common way people become infected. Floodwaters, runoff, and overflowing sewage systems exacerbate these risks.

It's important to note that some water-related diseases, such as malaria, are transmitted by vectors (e.g., mosquitoes) that breed in water. Efficient drainage systems can control vector populations by eliminating their aquatic breeding habitats.

For more information on the mechanisms of disease spread, refer to our guide on microorganism disinfection.

Prevention Strategies

Clean water and effective sanitation are fundamental to reducing the incidence of waterborne diseases. The provision of safe drinking water and the proper disposal of faeces are critical preventive measures.

Water Disinfection

Disinfection is a cornerstone of water treatment, aiming to kill existing pathogens in the water supply and prevent their regrowth within the distribution system. Without adequate disinfection, the risk of waterborne disease outbreaks significantly increases.

The choice of disinfectant depends on various factors, including raw water quality, the specific pathogens targeted, and the design of the water supply system.

Two primary methods for inactivating microorganisms in water are widely employed:

  1. Oxidation with Chemicals:
  2. Irradiation:
    • Ultraviolet (UV) radiation

These methods are crucial for safeguarding public health by providing a continuous supply of pathogen-free drinking water.

AquaChain Engineering Tip

When assessing the efficacy of disinfection against waterborne pathogens, always consider the CT (Concentration × Time) value. For chemical disinfectants, a higher concentration or longer contact time is typically required to achieve a specific log reduction of microorganisms. However, understand that different pathogens have varying susceptibilities; for instance, Cryptosporidium oocysts are highly resistant to chlorine but are more effectively inactivated by UV light or ozone at practical doses. Tailor your disinfection strategy to the specific raw water challenges and target pathogen profiles.

Frequently Asked Questions

Q1: What are the primary ways water becomes contaminated with disease-causing agents?

A1: Water commonly becomes contaminated through contact with human or animal faeces containing pathogenic microorganisms. This can occur via inadequate sanitation, runoff from agricultural lands or urban areas, leaky sewer systems, and floodwaters entering drinking water sources.

Q2: Why are waterborne diseases still such a significant global health challenge despite advances in technology?

A2: Waterborne diseases persist as a major challenge due to insufficient access to improved drinking water sources and adequate sanitation for billions of people, particularly in developing regions. Climate change, urbanization, and aging infrastructure can also exacerbate contamination risks.

Q3: What is the role of disinfection in preventing waterborne diseases, and what are common methods?

A3: Disinfection is crucial for inactivating pathogens present in water supplies and preventing their regrowth in distribution systems. Common methods include chemical oxidation with substances like chlorine, chlorine dioxide, or ozone, and physical irradiation using ultraviolet (UV) light.