Viral Risks Of Polluted Water: A Health Concern

Waterborne viruses are frequently implicated as the cause of water-related gastrointestinal illness. Waterborne disease outbreaks (WBDOs) are reported each year and are associated with recreational water, treated drinking water, and groundwater. The actual source of contamination can vary; however, the two common threads are (1) the introduction of fecal material into the water source and (2) inadequate or interrupted treatment of water intended for drinking.

Waterborne viruses can be introduced into our recreational and finished drinking water sources through a variety of pathways ultimately resulting in the onset of illness in a portion of the exposed population. The transmission of viruses in water has a significant impact on public health. Contaminated groundwater and recreational water cause the majority of virus-related WBDOs. Noroviruses are the dominant cause of WBDOs in high-income countries.

Waterborne viruses of primary concern include noroviruses, Hepatitis A virus, Hepatitis E virus, adenovirus, astrovirus, enteroviruses, and rotavirus. Although viruses implicated in WBDOs are capable of causing a variety of acute illnesses, acute gastrointestinal illness (AGI) is most commonly reported.

Waterborne viruses are one of the emerging biological contaminants responsible for the sporadic outbreak of waterborne illnesses worldwide. Compared with bacteria and protozoa, viruses are smaller, measuring between 20 and 350 nm in diameter. Viruses are obligate intracellular parasites containing bundles of gene strands of either RNA or DNA as a core nucleic acid surrounded by a protective coat called protein capsid.

The public health impact of the transmission of viruses in water is significant worldwide. Even though viruses are not the only pathogens present in water that can cause disease, the risk of illness is 10–10,000 times greater for viruses than bacteria at a similar level of exposure.

Waterborne viruses and their effects on public health

Waterborne viruses can be introduced into recreational and drinking water sources through a variety of pathways, ultimately resulting in the onset of illness in a portion of the exposed population. The transmission of viruses in water has a significant impact on public health.

Waterborne viruses are frequently implicated as the cause of water-related gastrointestinal illness. Waterborne disease outbreaks (WBDOs) are reported each year and are associated with recreational water (RW), treated drinking water (DW), and ground water (treated and untreated). Depending on the water source, the actual source of contamination can vary; however, the two common threads are:

• The introduction of faecal material into the water source
• Inadequate or interrupted treatment of water intended for drinking

Contaminated groundwater and recreational water cause the majority of virus-related WBDOs. Noroviruses are the dominant cause of WBDOs in high-income countries.

Waterborne viruses and their occurrence in water sources

Waterborne viruses are frequently implicated as the cause of water-related gastrointestinal illness. Waterborne disease outbreaks (WBDOs) are reported each year and are associated with recreational water (RW), treated drinking water (DW), and groundwater (treated and untreated). The occurrence of human enteric viruses in water remains largely unknown unless an outbreak is reported and samples are collected since water sources are not routinely tested for viruses.

The two common threads in the contamination of water sources are:

• The introduction of faecal material into the water source
• Inadequate or interrupted treatment of water intended for drinking

Human enteric viruses may be introduced into the water environment through various routes, including:

• The discharge of sewage-contaminated water into RW and/or DW sources
• The land application of municipal biosolids
• Groundwater impacted by surface water or proximity to faulty septic systems and leaking sewers
• The discharge of untreated wastewater or inadequately treated wastewater effluent

The actual source of contamination can vary depending on the water source.

Treated Drinking Water

There is a specific focus on DW derived from treated surface water as opposed to treated groundwater that is used as DW. In the US, Keswick et al. (1984) reported 83% of samples to be positive for either rotavirus or enteroviruses. However, few studies on virus occurrence in DW in the US have been reported since, and in more recent studies, no viruses were detected.

In international settings, there is more research related to determining the occurrence of viral pathogens in DW. Studies have reported the presence of norovirus, adenovirus, enterovirus, and hepatitis A virus in DW samples.

Groundwater (Treated and Untreated)

One of the greatest fallacies regarding groundwater (GW) as drinking water is that it is more likely to be free of pathogenic microorganisms due to its presumed natural filtering abilities. However, pathogen-contaminated GW can often be attributed to failing or poorly sited septic systems. Several studies over the past decade have demonstrated the widespread occurrence of human enteric viruses in both individual and municipal wells in the US.

For an international perspective, a study on norovirus occurrence in GW sources in South Korea reported 17-22% norovirus-positive samples out of 300 collected and analysed.

Recreational Water

Most data available on the occurrence of enteric viruses in RW sources is related to untreated venues such as lakes, rivers, and marine beaches, as opposed to treated venues (i.e. waterparks, pools). Virus-related WBDOs can occur in both venues. Overall, RW has a high occurrence of human enteric viruses depending on the water type and virus.

Waterborne Disease Outbreaks (WBDOs) Due to Viruses

United States

From 2003 to 2010, 12 virus-related WBDOs were caused by contaminated DW—all from GW sources. Reported outbreaks were caused predominantly by noroviruses, with two outbreaks caused by hepatitis A virus. Of the 26 virus-related WBDOs reported from 2003 to 2008, more than half were due to contaminated RW sources—both treated and untreated. The dominant viral etiologic agents were human noroviruses, followed by one outbreak due to an enterovirus.

International

Determining the occurrence of virus-related WBDOs outside of the US is challenging, with more data available for high-income countries. Data available through the European Environment and Health Information System states that from 2000 to 2007, there were 148 WBDOs caused by enteric viruses—136 due to contaminated DW and 12 due to contaminated RW sources.

Waterborne viruses and their removal

Waterborne viruses are a significant public health concern, with contaminated groundwater and recreational water being the primary sources of virus-related waterborne disease outbreaks (WBDOs). Noroviruses are the most common cause of WBDOs in high-income countries. However, Hepatitis A and E viruses, rotavirus, adenovirus, astrovirus, and enteroviruses are also frequently implicated in WBDOs. These viruses are often transmitted through the ingestion of contaminated drinking water or recreational water, leading to acute gastrointestinal illness.

The occurrence of viral pathogens in water sources is challenging to determine due to the lack of routine testing for viruses and the limitations of sampling and detection methods. However, studies have detected the presence of viral pathogens in treated drinking water, groundwater, and recreational water sources worldwide. Treated drinking water, especially from groundwater sources, is less frequently tested for viral pathogens, and the available data is limited. Groundwater is often assumed to be safer than surface water due to natural filtration processes, but this assumption is incorrect, as viruses can easily contaminate groundwater through sewage, faulty septic systems, and leaking sewers.

The removal and inactivation of waterborne viruses can be achieved through various treatment options, ranging from point-of-use (POU) household water treatment to advanced membrane filtration technologies in centralized drinking water treatment plants (DWTPs). Chlorination is the most commonly used disinfectant worldwide and is effective against most viruses. However, chlorination may produce toxic disinfection by-products, and it is ineffective against Cryptosporidium, a protozoan that causes diarrhea. Other disinfection methods, such as monochloramine, ultraviolet (UV) light, chlorine dioxide, and ozone, are also effective against viruses but have their own limitations, such as the production of other by-products or operational challenges.

Advanced membrane filtration technologies, such as ultrafiltration, are highly effective in removing all classes of microorganisms, including viruses, from drinking water sources. However, there is no single "silver bullet" treatment that is effective against all virus types and water quality conditions. The inactivation of viruses by disinfectants depends on various factors, including the type of disinfectant, water chemistry, and the specific virus and its genome and capsid structure.

Polluted water, especially water contaminated with viral pathogens, can indeed cause acute viral syndrome. Waterborne viruses can be introduced into recreational and drinking water sources through various pathways, leading to illness in a portion of the exposed population. The ingestion of contaminated water is a significant route of transmission for viral pathogens, and inadequate or interrupted treatment of drinking water can increase the risk of infection.

Waterborne viruses and their detection

Waterborne viruses are frequently implicated as the cause of water-related gastrointestinal illness. Waterborne disease outbreaks (WBDOs) are reported each year and are associated with recreational water, treated drinking water, and groundwater. The actual source of contamination can vary; however, the two common threads are (1) the introduction of fecal material into the water source and (2) inadequate or interrupted treatment of water intended for drinking.

The occurrence of human enteric viruses in water remains largely unknown unless an outbreak is reported and samples are collected since water sources are not routinely tested for viruses. Moreover, there are challenges related to sampling studies to determine virus presence due to both differences and limitations in recovery and concentration methods for the detection of viruses in water.

The options available to treat water for the removal and/or inactivation of enteric viruses range from low-tech (i.e. household water treatment) to high-tech (i.e. drinking water treatment plants utilizing advanced membrane filtration processes). Treatment options tend to focus solely on the removal of bacteria, therefore, some of the technologies described below were never initially designed for the removal of viruses.

The public health impact of the transmission of viruses in water is significant worldwide. Waterborne viruses can be introduced into our recreational and finished drinking water sources through a variety of pathways ultimately resulting in the onset of illness in a portion of the exposed population.

Waterborne viruses and their impact on children

Waterborne viruses are a significant cause of disease and death, particularly in children. These viruses are transmitted through contaminated drinking water and recreational water. They can cause a range of illnesses, including acute viral syndrome, with symptoms such as vomiting and diarrhoea being the most commonly reported.

Waterborne viruses can be introduced into recreational and drinking water sources through various pathways, ultimately resulting in illness in a portion of the exposed population. While there have been advances in drinking water treatment technologies and source water protection strategies, waterborne disease outbreaks due to viral pathogens still occur each year worldwide.

Human enteric viruses are those that colonise the gastrointestinal tract. These viruses are excreted in large amounts in the stool of infected persons and are highly stable in the environment. They can infect both surface and groundwater and do not multiply outside of their host. The effectiveness of water treatment methods remains limited with respect to these microorganisms.

The most common waterborne viruses include norovirus, hepatitis A and E viruses, adenovirus, astrovirus, enteroviruses, and rotavirus. These viruses are responsible for various pathologies, such as gastroenteritis, hepatitis, paralysis, meningitis, or respiratory diseases.

Norovirus is the dominant cause of waterborne disease outbreaks in high-income countries and is highly resistant to inactivation by both UV and chlorine. Hepatitis A and E viruses are more common in low-income countries without adequate water and sanitation.

The impact of waterborne viruses on public health is significant worldwide, and the risk of illness is 10–10,000 times greater for viruses than bacteria at a similar level of exposure. The current bacterial indicator-based methods for evaluating water quality are often ineffective proxies for pathogenic viruses.

Strategies to Reduce the Impact of Waterborne Viruses on Children's Health

• Improving access to safe drinking water and sanitation, particularly in rural and peri-urban areas of developing countries.
• Developing and implementing effective water treatment protocols and sensors to rapidly detect and quantify infectious viruses in finished drinking water.
• Enhancing surveillance systems and reporting of waterborne disease outbreaks, especially in low-income countries.
• Investing in ageing drinking water distribution systems and wastewater infrastructure, especially in large cities.
• Promoting handwashing and hygiene practices to reduce the spread of waterborne viruses.
• Educating communities about the risks associated with contaminated water and how to prevent exposure.

Frequently asked questions