Common themes contributing to recent drinking water disease outbreaks in af ﬂ uent nations

New Zealand experienced its largest waterborne disease outbreak in modern history in August 2016 with 5,500 cases and four fatalities. This recent outbreak is one of 24 drinking-waterborne disease outbreaks in af ﬂ uent nations that have been reported in the scienti ﬁ c literature since the infamous Walkerton, Ontario, Canada fatal outbreak (2,300 cases, seven fatalities) in May 2000. These disasters were all eminently preventable given the economic and intellectual resources existing in the countries where they occurred. These outbreaks are analysed according to major recurring themes, including: complacency, naiveté and ignorance, failure to learn from experience and chemophobia . Lessons that can be learned to improve preventive approaches for ensuring safe drinking water are based on an extensive and authentic body of evidence in support of meaningful improvements. Philosopher George Santayana captured this need with his famous quote: ‘ Those who cannot remember the past are condemned to repeat it . ’ content="Abstract. New Zealand experienced its largest waterborne disease outbreak in modern history in August 2016 with 5,500 cases and four fatalities. This recent ou

INTRODUCTION Surprisingly, despite having the economic and knowledge resources to eliminate them, drinking-waterborne disease outbreaks in developed countries keep occurring (Hrudey & Hrudey , ). Public health risk can never be managed to zero, particularly when there is a substantial human element involved in causation. However, a review and analysis of the occurrence and causes of drinking-waterborne disease outbreaks in developed countries reveals a depressing contribution and role for ignorance and complacency, even among supposedly trained and knowledgeable practitioners. The observed ignorance and complacency is difficult to reconcile with the readily available evidence that should enable the concerned practitioners to avoid such disasters. This review summarizes common causal themes from 24 drinking-waterborne disease outbreaks in affluent nations since the infamous fatal outbreak in Walkerton, Canada, in May 2000.

MATERIALS AND METHODS
In this paper, the discussion has been developed from an analysis of the circumstances and factors contributing to drinking-waterborne disease outbreaks in jurisdictions 2004, 2014 which had the resources, both economic and technical, to avoid such public health disasters. A comprehensive data base of published reports of drinkingwaterborne disease outbreaks in developed countries was created and maintained. The data base was initiated by collecting English language publications in the peer-reviewed scientific literature from fields including epidemiology, public health, water quality and environmental engineering.
The collected publications were supplemented by official investigation reports and documented public inquiries produced in whatever local language they were accessible (Hrudey & Hrudey ).

RESULTS AND DISCUSSION
The 24 outbreaks occurring since 2000 and their salient features are summarized in Table 1. Only salient details of each outbreak are provided. However, details in support of the themes that are discussed below are evident in the references cited for each outbreak in Table 1.

Major recurring themes contributing to failure
The scope of commentary on the highlighted outbreaks is intentionally concise, but a more expansive explanation and documentation of the themes summarized below can be accessed online at Hrudey (). The publication (Hrudey )    (continued) Downloaded from https://iwaponline.com/ws/article-pdf/19/6/1767/578191/ws019061767.pdf" /><meta name="description" content="Abstract. New Zealand experienced its largest waterborne disease outbreak in modern history in August 2016 with 5,500 cases and four fatalities. This recent ou and must be regarded as a public-health threat to any drinking-water supply.
Today, we have progressed well past our knowledge of a few decades ago when science had not yet characterized previously unrecognized threats to safe drinking water, like Cryptosporidium oocysts. New pathogens will inevitably be discovered in the future, but the reality is that all microbial pathogens are microscopic particles that must pass through drinking-water systems in a viable state such that they can reproduce in a susceptible host and cause illness. These realities mean that water treatment that achieves effective fine-particle removal and disinfection that inactivates any pathogens not removed will prevent drinking-water disease outbreaks regardless of the genetic make-up of the pathogen.
The cases reviewed involve disturbingly simple failures such as not preventing livestock access or human sewage discharges from contaminating source waters. These are threats to drinking-water safety that are entirely well known and thoroughly characterized. Complacency, naiveté and ignorance seem to offer the only rational explanation as to why such events keep happening throughout the developed world.
Perhaps most frustrating is the myth that raw water supplies can be 'pristine' when it is clear that contamination

Failure to learn from experience
Considering the recurring failures that are evident in the 24 outbreaks cited in this paper and summarized in Table 1, water purveyors are not universally learning from experience with failure. The lessons that need to be learned are not that complex, so we can only conclude there is a systematic failure to communicate these rather basic lessons to all those individuals who are responsible for providing safe drinking water for the public. We cannot imagine that such individuals would knowingly wish to make their consuming public ill. A more likely explanation is that such individuals have not been adequately trained to recognize and to avoid conditions that will allow such eminently preventable drinking-waterborne outbreaks from happening.
To that end, we all have a responsibility to communicate

Chemophobia
Any time dedicated to reviewing research on drinking-water quality and resulting standards for drinking water will reveal a preponderance of text discussing chemical contaminants versus microbial pathogens. A novice to the field could be forgiven for concluding that chemical contaminants pose a greater threat to human health than microbial pathogens. An enormous amount of attention has been directed to disinfection by-products (Hrudey & Fawell ). Because microbial pathogens pose such well-documented, certain public-health risks to drinking water, disinfection has long been recognized as essential for ensuring safe drinking water. All disinfectants produce disinfection by-products to some degree, but chlorination, as the most common and cost-effective means of drinking-water disinfection, has received the most research attention. Despite an enormous number of research investigations, only a possible causal link with urinary bladder cancer has retained some credibility, but definitely far from certainty in epidemiologic evidence (Hrudey et al. ). The public-health risk from disinfection by-products is negligible where chlorination is regulated, yet a fear of chlorination over its possible health effects has allowed inadequate disinfection that has unfortunately been a contributing factor in many drinkingwaterborne disease outbreaks. Opposition to chlorine disinfection was clearly a major factor in many of the listed outbreaks in Table 1  to develop the water-safety plan approach for drinkingwater quality management. This risk management approach, which identifies threats to drinking-water safety and focuses on effective operations, has been enshrined in their respective drinking-water guidelines (WHO ; NHMRC ).
Conceptually, the water safety plan approach is much superior to a narrow focus strictly on numerical water-quality criteria for preventing the factors contributing to the outbreak failures documented in Table 1. However, it is noteworthy that two of the utilities experiencing outbreaks,

Nokia in 2007 (Hrudey & Hrudey ) and Havelock
North in 2016 (Government of New Zealand ), had water-safety plans. Evidently, having a water-safety plan that is not carefully prepared and scrupulously followed will not prevent an outbreak.

CONCLUSIONS
Despite unprecedented knowledge about public health, drinking-water quality and safety, at least 24 outbreaks of waterborne disease in affluent nations have occurred in the period from 2001 to 2016. The contributing causes are not obscure and the outbreaks are inherently preventable.
The identified causes suggest a need for an expanded commitment to informing operational personnel, managers and regulators about the authentic negative experience in such outbreaks.
Adoption of a water-safety plan approach offers an opportunity to prevent waterborne disease outbreaks. However, the fact that two of the water utilities that experienced outbreaks had water-safety plans indicates that the quality of and commitment to implementing a water-safety plan are essential to achieving any preventive benefit.
The ongoing occurrence of such observed, preventable waterborne disease outbreaks should lead water managers to take all reasonable steps under their influence to ensure that such failures are not allowed to occur within the systems for which they are responsible. Philosopher George Santayana captured this need to learn from experience with his famous quote: 'Those who cannot remember the past are condemned to repeat it.'