Infectious Diseases: Water Pollution's Hidden Cause?

Waterborne diseases are a significant global health concern, particularly in developing regions with inadequate sanitation and hygiene. Infectious diseases transmitted through contaminated water can cause severe illnesses such as cholera, typhoid fever, hepatitis A, and dysentery. These diseases are often spread through the faecal-oral route, where contaminated water plays an intermediate role. Poor water quality, sanitation, and hygiene practices contribute to the spread of waterborne pathogens, leading to outbreaks and hospitalizations, especially in vulnerable populations. The impact of water pollution on human health is significant, with unsafe water being a leading risk factor for health burdens in developing regions.

Diarrhoeal diseases

The link between water quality and diarrhoeal diseases is well-established, and interventions to improve water quality have consistently resulted in a reduced incidence of diarrhoeal diseases. However, the specific pathogens responsible for the bulk of the disease can be challenging to identify due to the various transmission routes and the multitude of infectious agents that can cause diarrhoea.

The Gruber and others review found that most studies collected water samples after or concurrently with surveys on diarrhoea incidence, making it difficult to establish a direct link between water quality and disease outcome. Additionally, the water collected on a particular day may not accurately reflect the quality of the water on preceding days, especially if household members change their behaviour and drink higher-quality water as a result of contamination.

To address these challenges, innovations such as direct testing for pathogens, high-volume sampling, more objective health endpoints, and improved study designs are needed to enhance our understanding of the relationship between water quality and diarrhoeal diseases.

Parasitic infections

Fecal matter is a common source of parasitic contamination in water. Pathogens from sewers, septic systems, and animal wastes can find their way into water supplies through various means, including wastewater overflow, nonfunctioning sewage systems, contaminated storm drains, and agricultural effluent. For example, liquid sewage from improperly arranged toilets, cesspools, and livestock farms can penetrate the soil and aquifers, leading to parasitic contamination of groundwater.

In a study conducted in a rural village in northern Laos, water samples from a local stream revealed the presence of several enteric pathogens, including E. coli and Shigella spp. Intestinal parasitic infections were prevalent, with high rates of helminth (68.9%) and protozoan (27.2%) infections detected in the village population. Similarly, surveys in Lao PDR and across Southeast Asia have shown that climatic, ecological, and socioeconomic conditions facilitate parasite transmission, resulting in relatively high rates of helminth and protist co-infections.

To prevent parasitic infections, it is crucial to ensure access to safe water sources and improve sanitation and hygiene practices. This includes proper wastewater treatment before discharge into nearby water bodies and the safe disposal of excreta. Additionally, regular testing of water sources for pathogens is essential, with coliform bacteria serving as a simple indicator of potential contamination. Public health surveillance plays a vital role in monitoring trends in waterborne diseases and guiding prevention strategies to protect communities from parasitic infections transmitted through contaminated water.

Viral infections

Hepatitis A virus (HAV) is another waterborne virus. It is transmitted by consuming contaminated food or water or by close contact with an infected person. It is a liver infection that usually goes away in a few weeks, but it can become severe and last several months. The best way to prevent HAV is by getting vaccinated, eating only thoroughly cooked hot food, and avoiding raw or undercooked food.

Hepatitis E virus (HEV) is also transmitted via the faecal-oral route and spreads through water bodies polluted with human faeces. It is believed to be the cause of sporadic outbreaks of hepatitis in developing countries in Africa, Asia, and Mexico. Genotypes 3, 4, and 7 are associated with zoonotic transmission and are found in advanced countries.

Other waterborne viruses include adenovirus (AdV), astrovirus, enteroviruses (EV), and rotavirus (RV). These viruses can cause a range of acute illnesses, with acute gastrointestinal illness (AGI) being the most commonly reported. Enteric viruses are host-specific and cannot replicate outside their host. They are introduced into recreational and drinking water sources through various pathways, ultimately resulting in illness in a portion of the exposed population.

The actual source of viral contamination in water can vary depending on the water source, but the two common factors are the introduction of faecal material and inadequate or interrupted treatment of drinking water. To prevent viral infections, it is crucial to ensure proper water treatment and sanitation. Methods such as flocculation, filtration, chlorination, and ozonation can effectively reduce virus concentrations in water. In developing countries, iodination is a promising water treatment method, although its long-term effects, especially on pregnant women and children, are not yet fully understood.

Poor water quality

Waterborne diseases disproportionately affect those in developing countries, where access to safe and clean water is limited. These waterborne pathogens can cause a range of illnesses, including gastrointestinal problems, liver infections, and severe diarrhoea, which can be life-threatening if dehydration occurs. For example, cholera, a waterborne disease, causes watery diarrhoea and can lead to death in 50-70% of untreated patients.

In developing regions, inadequate water supplies, poor sanitation, and hygiene issues contribute to the spread of infectious diseases. This is particularly true for hepatitis A and E, which are associated with these factors. Poor sanitation also leads to early infection in children, who develop lifelong protection from the severe effects of hepatitis A that can occur in unexposed individuals in developed regions who contract the disease at an older age.

Additionally, microbial contamination of drinking water can transmit diseases such as dysentery, typhoid, and polio. Dysentery, caused by bacteria, viruses, or parasites in contaminated food and water, can be prevented through proper handwashing and hygiene practices. Typhoid is transmitted through the faeces and urine of infected individuals, and people become infected by consuming contaminated food or water. Polio, while nearly eradicated, has seen recent outbreaks in densely populated cities in India due to the presence of large urban slums.

To address these issues, the World Health Organization (WHO) leads global efforts to prevent water-related diseases by advising governments on developing health-based targets and regulations. The WHO provides drinking-water quality guidelines and supports countries in implementing them through practical guidance and direct country support. These guidelines are based on managing risks and promoting a framework for safe drinking water, which includes establishing health-based targets and developing and implementing water safety plans.

Sewage contamination

Human activities contribute significantly to sewage contamination. Household chemicals, personal hygiene products, and pharmaceuticals all contribute to the problem. Aging and inadequate wastewater infrastructure, including sewer pipes and treatment plants, further exacerbates the issue. As a result, sewage spills and backups occur, leading to the release of untreated wastewater into the environment. According to the United Nations, more than 80% of the world's wastewater is discharged back into the environment without proper treatment, with the figure being even higher in less developed countries.

The health risks associated with sewage contamination are significant. Waterborne diseases, such as cholera, giardia, and typhoid, can be contracted from contaminated water sources. Hepatitis A, a liver infection caused by consuming contaminated food or water, is another concern, especially for those living in developing countries or rural communities with poor sanitation and hygiene practices. Additionally, Legionella, a severe form of pneumonia, has been linked to water sources like cooling towers and piped water, resulting in hospitalizations and deaths.

The impact of sewage contamination extends beyond human health. Natural ecosystems, including coral reefs, salt marshes, and fish-rich river systems, are also at risk. High levels of sewage contamination elevate concentrations of nutrients, pathogens, endocrine disruptors, heavy metals, and pharmaceuticals in these ecosystems, threatening their health and biodiversity. This crisis demands innovative solutions and cross-disciplinary collaboration between conservationists and the human health sector to address effectively.

To mitigate the effects of sewage contamination, it is essential to invest in improving wastewater infrastructure and treatment processes. This includes upgrading sewer pipes, expanding and modernizing treatment plants, and implementing effective regulations and water management programs. Additionally, public health surveillance and outbreak response programs are crucial for monitoring and addressing waterborne diseases. By addressing these issues, we can reduce the health and environmental risks associated with sewage contamination and work towards ensuring safe and accessible water sources for all.

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