Waterborne diseases are diseases caused by pathogenic micro-organisms, such as bacteria, viruses, protozoa, and parasitic worms, that are transmitted through contaminated water. Many of these micro-organisms are intestinal parasites, invading the tissues or circulatory system through walls of the digestive tract. Various other waterborne diseases are caused by viruses. Other important classes of waterborne diseases are caused by metazoan parasites. Typical examples are certain Nematoda, or "roundworms", which may result in diseases such as Dracunculiasis or even guinea worm disease. Another class of waterborne metazoan pathogens is Schistosomatidae, a family of blood flukes. In addition to pathogens, water contamination may also be driven by chemical pollutants such as volatile organic compounds (VOCs). These include benzene, toluene, ethylbenzene, and xylenes, which can enter water lines through industrial dumping, pipeline leaks, jet fuel spills, or heat-damaged plastic pipes.
These diseases can spread through bathing, washing, drinking contaminated water, or eating food that has been exposed to contaminated water. While diarrhea and vomiting are the most commonly reported symptoms of waterborne illnesses, other symptoms may include nausea, stomach cramps, fever, and skin, ear, respiratory, or eye problems. Exposure to water contaminated with VOCs has been associated with headaches, nausea, tumor formation, and an increased risk of cancer, including leukemia. Waterborne diseases contribute significantly to mortality and disability worldwide, particularly in developing regions.
The most effective mechanism for preventing waterborne disease is reliable access to clean water, sanitation, and hygiene (WASH). This includes improving sanitation systems, chlorination, vaccination, and desalination. Infrastructure improvements, such as replacing damaged plastic pipes with metal ones in wildfire-prone areas, may also reduce the risk of contamination. Climate change increases the risk of waterborne diseases via the increased likelihood of droughts and floods, which can spread contaminants and disproportionately affect vulnerable populations. Surveillance can help monitor and prevent outbreaks. Historically, advances in sanitation, filtration, chlorination, and microbiology have helped scientists understand and control of waterborne diseases.
Terminology
The term "waterborne disease" is reserved largely for infections that are predominantly transmitted through contact with or consumption of microbially polluted water. Many infections may be transmitted by microbes or parasites that have entered the water accidentally, perhaps due to exceptional circumstances. However it may not be useful to categorize a disease as "waterborne" just because it may occasionally be transmitted by water. Diseases such as malaria are commonly mistaken as "waterborne" because mosquitos, acting as vectors, have aquatic stages in their life cycle. Controlling or treating still water can reduce mosquito populations, suggesting the idea that the disease is transmitted through water and not mosquito bites.
A related term is "water-related disease" which is defined as "any significant or widespread adverse effects on human health, such as death, disability, illness or disorders, caused directly or indirectly by the condition, or changes in the quantity or quality of any water". Water-related diseases are grouped according to their transmission mechanism: water borne, water hygiene, water based, water related. The main transmission mode for waterborne diseases is ingestion of contaminated water.
Causes
Lack of clean water supply, sanitation and hygiene (WASH) are major causes of the spread of waterborne diseases. The fecal–oral route is a transmission pathway for waterborne diseases. Poverty also increases the risk of communities being affected by waterborne diseases. For example, the economic level of a community may affect its access to clean water. Less developed countries might be more at risk of waterborne disease outbreaks than more developed regions. Additionally, 1 in 4 people, or 2.1 billion people globally, currently do not have access to safe drinking water.
Socioeconomic factors The lack of education in impoverished regions often results in waterborne disease. If local people are aware of an issue, they can take action to solve the problem domestically rather than relying on foreign counties for aid. Many countries in the Middle East, South East Asia, and Sub-Saharan Africa are prone to these issues because they lack advanced education. For example, Morocco has insufficient labor supply for the production of food and other work forces that could be well maximized. In response, the United States, Morocco and many other agencies worked together to initiate the H2O Maghreb Partnership. This educates the people of Morocco on clean water and sanitization through simulations of water treatment. Not only do the virtual reality technologies but recreate rare emergency circumstances for practice and also provide jobs for the citizens in under-developed countries to help the economy.
Political turmoil and war stimulate the transmission of waterborne disease in addition to lack of education. Countries in the Eastern Mediterranean Region deal with this issue especially. The World Bank has classified Yemen, along with several other countries in the Eastern Mediterranean Region, as "fragile and conflict-affected countries". Syria and Lebanon had not seen any outbreaks of cholera in about three decades, but it reappeared in 2022. War destroys the infrastructure needed for clean water and sanitization structures: a recipe for disease to spread. Two years ago the World Health Organization changed the status of cholera to a Grade 3 global public health emergency. Between the years 2016 and 2022 Yemen saw 2.5 million cases of cholera. These outbreaks are closely tied to the conflicts in the region. War also destroys the necessary medical facilities and hospitals to take care of patients who have contracted the waterborne diseases. In the Eastern Mediterranean Region, countries are no longer grappling with a pandemic, but rather an endemic.
Other war-torn regions such as Gaza must manage complex water systems which present more danger to the quality of water and chance of waterborne disease being present. Gaza gets the majority of its water from underground, but also some from Israel; they also have several desalination plants across the region. Workers are constantly working to fix water pipeline systems that have been destroyed by artillery in the war but are sometimes killed in the process.
As a comparison of a safe country's and a war-torn country's water consumption, Americans use about 300 liters per day while in Gaza a person would use about 80 liters per day. With every part of the water system in Gaza suffering harm in some shape or form by 2024, waterborne disease cases shortly thereafter exploded with 600,000 cases of acute diarrhea and even a 10 month old with polio.
Nature Communications published a 2022 study which measured the associations between racial and ethnic communities and concentrations of contaminants in drinking water from 2000 to 2011 in the United States. Counties with a greater proportion of Hispanic and Native American residents contained higher concentrations of arsenic and uranium in drinking water. However, non-Hispanic White residents had lower concentrations. The authors concluded that disparities in drinking water quality vary by region and demographic composition, representing the inequalities in exposure to regulated drinking water in the United States.
Africa The waterborne disease burden in Africa is severe and, in several ways, not comparable with anywhere else in the world. Decades of underinvestment in water infrastructure, rapid population growth and the persistent gap between urban and rural service delivery have left millions of people without reliable access to safe water. As of 2022, just 31% of sub-Saharan Africa's population used safely managed drinking water, less than half the global average of 73%; and only 24% had access to safely managed sanitation. By 2020, 418 million people on the continent still lack basic drinking water service, while 779 million had no basic sanitation, among them 208 million who continued to practice open defecation.
The consequences show up most gravely in child mortality. Diarrheal disease kills an estimated 600,000 people a year in sub-Saharan Africa, most of them being children under five and elderly adults, making it the third-leading cause of death in that age group across the region. What makes this particularly troubling is that the figure is almost certainly an undercount. Around 56% of African countries have no systematic waterborne pathogen surveillance in place, so outbreaks go unrecorded and deaths unattributed. Africa is believed to lead the world in diarrheal disease mortality, yet the data needed to fully confirm or address that reality largely is insufficient.
Influence of climate change
Climate change influences the growth and survival of bacteria and other pathogens in food and water systems.IPCC, 2022: Summary for Policymakers [H.-O. Pörtner, D.C. Roberts, E.S. Poloczanska, K. Mintenbeck, M. Tignor, A. Alegría, M. Craig, S. Langsdorf, S. Löschke, V. Möller, A. Okem (eds.)]. In: Climate Change 2022: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change [H.-O. Pörtner, D.C. Roberts, M. Tignor, E.S. Poloczanska, K. Mintenbeck, A. Alegría, M. Craig, S. Langsdorf, S. Löschke, V. Möller, A. Okem, B. Rama (eds.)]. Cambridge University Press, Cambridge, UK and New York, NY, USA, pp. 3–33, doi:10.1017/9781009325844.001. It affects waterborne diseases by influencing water temperature, water quality, sanitation, and microbial ecology.Cissé, G., R. McLeman, H. Adams, P. Aldunce, K. Bowen, D. Campbell-Lendrum, S. Clayton, K.L. Ebi, J. Hess, C. Huang, Q. Liu, G. McGregor, J. Semenza, and M.C. Tirado, 2022: Chapter 7: Health, Wellbeing, and the Changing Structure of Communities. In: Climate Change 2022: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change [H.-O. Pörtner, D.C. Roberts, M. Tignor, E.S. Poloczanska, K. Mintenbeck, A. Alegría, M. Craig, S. Langsdorf, S. Löschke, V. Möller, A. Okem, B. Rama (eds.)]. Cambridge University Press, Cambridge, UK and New York, NY, USA, pp. 1041–1170, doi:10.1017/9781009325844.009.
Climate change plays a major role in the socioeconomic impact of waterborne disease, especially in informal settlements. Over 60% of Africa's urban population lives in areas with limited water and sanitation infrastructure. Droughts have been linked to cholera outbreaks in Nairobi, while flooding can spread pathogens through contaminated water.
Warmer waters, increased flooding, precipitation and humidity promote the growth and spread of bacteria such as Vibrio cholerae, which causes cholera, and other pathogens responsible for gastroenteritis, wound infections and diarrheal diseases. Higher water temperatures can also increase the yield of bacteria from drinking water delivery systems and during periods of warmer temperatures water consumption rates are also typically higher. Together these increase the probability of pathogen ingestion and infection.
Heavy rainfall and flooding caused by climate change can also affect pathogen transmission via impacts on sanitation and/or drinking water treatment infrastructure, contaminating drinking water sources or food products. Floods can overwhelm water systems, causing backflow that lead to contamination of groundwater and other drinking water sources.
Diseases by type of pathogen
Protozoa