The global water quality situation

Today, 2 billion people lack access to safely managed drinking water services and 3.6 billion people lack safely managed sanitation services. Unsafe hygiene practices are widespread, compounding the effects on people’s health. The impact on child mortality rates is devastating, with more than 300,000 children under five who die annually from diarrhoeal diseases due to poor sanitation, poor hygiene, or unsafe
drinking water.

Under-fives living in countries experiencing protracted conflict are 20 times more likely to die from causes linked to unsafe water and sanitation than from direct violence.


The impact of universal access to water, sanitation and hygiene on global health would be profound. There is the potential to save the lives of the 830,000 people who currently die every year from diseases directly caused by these issues, and we could also drastically reduce child malnourishment and help alleviate physical and mental under-development.



No access to good quality drinking water leads to a high risk of water-borne diseases such as diarrhoea, cholera, typhoid fever, hepatitis A, dysentery, and other diarrhoeal diseases. Each year 4 billion cases of diarrhoea cause 2.2 million deaths, mostly among children under the age of five. Apart from the high infant mortality, diarrhoea affects numerous children in developing countries in their physical development. Frequent diarrhoea is a cause for children’s malnutrition, while malnutrition again increases the likelihood for children to die from other infectious diseases. Today, 50% of child malnutrition is associated with unsafe water, inadequate sanitation and poor hygiene, while recent estimates suggest that malnutrition is an associated cause for about half of all deaths occurring among children in developing countries.



Sanitation infrastructures are essential as well. Without facilities that safely separate human waste from human contact, people have no choice but to use inadequate communal latrines or to practise open defecation. In the immediate environment, exposed faecal matter will be transferred back into people’s food and water resources, helping to spread serious diseases like cholera. Beyond the community, the lack of effective waste disposal or sewerage systems can contaminate ecosystems and contribute to disease epidemics.

Globally, around 80% of wastewater flows back into the ecosystem without being treated or reused.


Access to water, sanitation and hygiene has profound wider socio-economic impacts, beyond the immediate, obvious advantages of people being hydrated and healthier. A person without access to adequate drinking water is forced to rely on sources such as surface water, unprotected and possibly contaminated wells, or vendors selling water of unverifiable provenance and quality. Besides, for many communities, water sources are usually far from their homes, and it typically falls to women and girls to spend much of their time and energy fetching water. World Health Organization found that 207 million people spend over 30 minutes per round trip to collect water from an improved source. Taking into account that approximately 50 litres of water per person per day are needed to ensure that most basic needs are met while keeping public health risks at a low level, the effort is noteworthy.


Hygiene promotion is the most cost-effective health intervention.


Loss of productivity to water- and sanitation-related diseases costs many countries up to 5% of GDP.

Transmission of waterborne pathogens

Waterborne pathogens belong to the groups of bacteria, viruses and parasites. Although viruses are often not detected in the water or the host, they may account for the largest group of causative agents, followed by parasites and bacteria.


Many common pathogens are not only transmitted through water but also follow other infectious pathways. Poor general hygiene practices often are a significant source of infection. Furthermore, secondary contamination of drinking water due to incorrect water handling is frequently observed in developing countries. Therefore, interventions aiming at improving the water quality should always consider introducing general hygiene messages. Through such combined measures, significant positive health effects in the target population can be achieved.



Well-known and widely distributed pathogens and their health significance are listed in the following table.

PathogenPathogen Health significance
Campylobacter jejuni y C. coliHigh
Escherichia coliHigh
Salmonella typhiHigh
Otras SalmonellaHigh
Shigella spp.High
Vibrio choleraeHigh
Yersinia enterocoliticaHigh
Pseudomonas aeruginosaModerate
Aeromonas spp.Moderate
Polio virusHigh
Hepatitis A virusHigh
Hepatitis non-A virusHigh
Norwalk VirusHigh
Norwalk -like viruses(NLV)Moderate
Entamoeba hystoliticaHigh
Giardia spp.High
Cryptosporidium spp.High

The bacteria Vibrio cholerae, Shigella, Salmonella and different pathogenic strains of E. coli are the most important water-borne pathogens. Gastrointestinal diseases caused by these bacteria can be serious, and usually treatment is required. Dehydration as a result of profuse diarrhoea is frequent among children under 5 years in the developing countries. Cholera epidemics are mainly caused by water borne Vibrio cholerae. Therefore, water treatment is the most important measure for the prevention of these epidemics.

Scanning electron micrograph of E. coli and E. faecalis.

Viral diseases are usually symptomatic and acute with relatively short disease periods, high viral shedding, low infectious dose and restricted host variety.


Even though helminths and protozoa are not often the cause of acute diarrhoea, they represent an important group of pathogens. An infection with protozoa may cause chronic digestion problems which lead to malnutrition. Malnourished children are much more likely to suffer from various kinds of infections. Giardia spp. and Cryptosporidium spp. are the two protozoa regularly transmitted through water. Both pathogens have a cystic stage, which is very resistant to environmental influences. It allows them to survive for a long time outside any host. Ingestion of the cysts may cause illness; however, silent infections are very common and support the spread of these pathogens.