By Kelly A. Reynolds, MSPH, PhD

One Health is an emerging scientific discipline that focuses on the relationship among humans, animals and the environment relative to health and disease development. Given that the majority of pathogens known to infect humans originate in animals, a comprehensive, multidisciplinary, One Health disease management approach is critical. Water is a primary environment facilitating the spread of illness between animals and humans and thus, serves as a key point of control.

The human-ecosystem interface
Although not new, scientific discovery from a One Health perspective is expanding rapidly. Early in its inception the concept was described as ‘One Medicine,’ an integration of human and animal medicine to address diseases spread between the two. Around 2004, there was broad recognition of the importance of incorporating environmental or ecological health with the One Medicine approach and One Health was born.1

Understanding how humans, animals and the ecosystem interact is an important component for addressing the most prevalent and emerging illnesses of our time. The majority of human infectious diseases originated in animals, including both domestic and wild animal populations. The same trend is evident in waterborne diseases as well. Animals are a concern relative to source-water protection and distribution intrusion events where environmental waters tainted with animal waste can infiltrate leaky drinking-water distribution pipes. Ecological events such as rainfall, flooding and other climatic changes further stress the availability, sustainability and overall quality of drinking water. These same events indirectly impact human and animal health by driving changes in population movement, interaction and overall health of a community.

Population needs have promoted the industrialization of farming practices where larger, more concentrated animal husbandry operations lead to increased point-source contamination events. Recent news headlines report a massive Salmonella outbreak from (and recall of) contaminated eggs and a national outbreak of E. coli from romaine lettuce. Given the current large-scale food production and distribution practices in the US, single-contamination events have the potential to affect much larger population sectors than in previous decades, where small-scale, local farming was more common.

A One Health timeline
The concept of One Health has evolved over the years, along with a growing recognition of the multiple factors contributing to health. Below is a timeline of landmark events in the evolution of One Health.2,3

During the mid-1800s, German scholar, Rudolf Virchow, identified the relationship between animal and human health, coining the term ‘zoonosis’ to describe the infectious link. He went on to become a major contributor to modern medical education and the future understanding of environmental health influencers. In 1964, Calvin Schwabe, an epidemiologist and doctor of veterinary medicine with a Master’s Degree in public health, promoted the idea of similarities between human and animal medicine and the need to control like-illnesses in each. He coined the term ‘One Health’ and later developed a novel epidemiology and veterinary science program at the University of California-Davis to advance the discipline.

By 2004, experts recognized the need for multidisciplinary collaborations at the interface of human and animal populations. Around this time, the Wildlife Conservation Society hosted an international gathering of human and animal health experts to outline priorities for addressing threats to humans and animals. Ultimately known as the 12 Manhattan Principles, the One Health, One World concept of global implications of animal/human interactions was further acknowledged.

Mounting fears of pandemic avian influenza (also known as bird flu) in 2007 drove widespread attention to avian-human considerations relative to emergency preparedness. Soon thereafter, the Centers for Disease Control and Prevention (CDC) established a One Health office and the American Medical Association (AMA) passed a One Health Resolution to promote collaboration between human and veterinary medicine.

Other agencies, including the Food and Agriculture Organization of the United Nations (FAO), the World Health Organization (WHO), the World Organization for Animal Health (OIE), the United Nations Children’s Fund (UNICEF), the World Bank and the United Nations System Influenza Coordination (UNSIC), formed interdisciplinary teams, organized conferences and developed strategic foci on the emerging field of One Health. Eventually, representatives from more than 60 countries would gather in Davos, Switzerland in 2012 for the first One Health Summit, sponsoredby the Global Risk Forum.

Today, the US federal government is considering legislation to advance emergency preparedness through the One Health Act of 2018 (Senate Bill S.2615). Introduced in March 2018, the bill is being reviewed by the Committee on Health, Education, Labor and Pensions. Ultimately, the act calls for the development of a One Health Framework for coordinated federal activities under the One Health Program.

Ensuring safe drinking water
The One Health concept is highly relevant to drinking water safety. More than half of infectious diseases in humans are of animal origin and more than three quarters of emerging illnesses have a zoonotic link. Water serves as a common conduit between wild and domestic animals and human exposures to animal diseases.

One of the largest waterborne outbreaks in US history occurred in 1993 in Milwaukee, WI. The etiological agent in the outbreak was Cryptosporium, a protozoan parasite, originating in nearby cattle-farm waste that spread to the community’s source drinking-water supplies. Approximately 400,000 people become ill (nearly half the city’s population) and over 100 died. There are many other examples of drinking-water outbreaks where the animal-human interface resulted in severe disease and death and where a One Health approach to policies and prevention is warranted.4,5 Zoonotic waterborne pathogens include commonly known hazards such as, E. coli O157:H7, Salmonella and Campylobacter, as well as rare hazards such as Entamoeba, Yersinia and Toxoplasma.

One means for evaluating a group of parameters aimed at preventing or treating waterborne zoonotic disease is known as the ‘control envelope.’4 A typical control envelope might include protection of source water from animal waste intrusion, water disinfection and antibiotic treatments. Pathogens are evaluated and prioritized based on their potential to exceed control-envelope parameters and cause significant health outcomes. Based on the example above, breaches may be due to poor animal waste control, inadequate disinfection or resistant bacterial strains. If properly maintained as per manufacturer suggestions, the control envelope of POU devices is difficult to exceed as a final protection barrier.

In the US and globally, the emergence or reemergence of zoonotic diseases is expected to increase due to variable water treatment and use patterns, population growth and vulnerability factors, globalization of travel and food distribution, climatic events and disasters, mutations and antibiotic resistance in microbes, concentrated animal husbandry practice and more. Although a holistic, One Health approach is recommended to minimize exposure to waterborne zoonotic pathogens, many variables are unpredictable or even impossible to prevent (i.e., Mother Nature). Therefore, controls at the source of exposure or point of use offer a multi-layered, broad-based approach to risk reduction. POU water treatment devices are an important part of the holistic approach to drinking-water quality management.


  1. Destoumieux-Garzón D, Mavingui P, Boetsch G, et al. The one health concept: 10 years old and a long road ahead. Frontiers in Veterinary Science. 2018;5(FEB). doi:10.3389/fvets.2018.00014
  2. USDA APHIS. The History of One Health. Published 2015. Accessed April 12, 2018.
  3. CDC. Timeline: People and Events in One Health. Published 2018. Accessed April 18, 2018.
  4. Cotruvo, J.A.; Dufour, A; Rees, G, et al. Waterborne Zoonoses: Identification, Causes, and Control. Waterborne Zoonoses Identification, Causes, Control. 2004:485 p. doi:10.2166/9781780405865
  5. Gannon, V., Laing, C/R. Waterborne zoonoses. Routledge Handbook of Water and Health; 2015:171-182. doi:10.4324/9781315693606

About the author
Dr. Kelly A. Reynolds is an Associate Professor at the University of Arizona College of Public Health. She holds a Master of Science Degree in public health (MSPH) from the University of South Florida and a doctorate in microbiology from the University of Arizona. Reynolds is WC&P’s Public Health Editor and a former member of the Technical Review Committee. She can be reached via email at [email protected]


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