Distribution System Operational Deficiencies Coincide with Reported Legionnaires' Disease Clusters in Flint, Michigan

It's getting hot in here: Effects of heat on temperature, disinfection, and opportunistic pathogens in drinking water distribution systems

As global temperatures rise with climate change, the negative effects of heat on drinking water distribution systems (DWDS) are of increasing concern. High DWDS temperatures are associated with degradation of water quality through physical, chemical and microbial mechanisms. Perhaps the most pressing concern is proliferation of thermotolerant opportunistic pathogens (OPs) like Legionella pneumophila and Naegleria Fowleri. Many OPs can be controlled in DWDS by residual disinfectants such as chlorine or chloramine, but maintaining protective residuals can be challenging at high temperatures. This critical review evaluates the literature on DWDS temperature, residual disinfectant decay, and OP survival and growth with respect to high temperatures. The findings are synthesized to determine the state of knowledge and future research priorities regarding OP proliferation and control at high DWDS temperatures. Temperatures above 40 °C were reported from multiple DWDS, with a maximum of 52 °C. Substantial diurnal temperature swings from ∼30-50 °C occurred in one DWDS. Many OPs can survive or even replicate at these temperatures. However, most studies focused on just a few OP species, and substantial knowledge gaps remain regarding persistence, infectivity, and shifts in microbial community structure at high temperatures relative to lower water temperatures. Chlorine decay rates substantially increase with temperature in some waters but not in others, for reasons that are not well understood. Decay rates within real DWDS are difficult to accurately characterize, presenting practical limitations for application of temperature-dependent decay models at full scale. Chloramine decay is slower than chlorine except in the presence of nitrifiers, which are especially known to grow in DWDS in warmer seasons and climates, though the high temperature range for nitrification is unknown. Lack of knowledge about DWDS nitrifier communities may hinder development of solutions. Fundamental knowledge gaps remain which prevent understanding even the occurrence of high temperatures in DWDS, much less the overall effect on exposure risk. Potential solutions to minimize DWDS temperatures or mitigate the impacts of heat were identified, many which could be aided by proven models for predicting DWDS temperature. Industry leadership and collaboration is needed to generate practical knowledge for protecting DWDS water quality as temperatures rise.

Racial and Ethnic Differences in Emotional Reactions to the Flint Water Crisis among Michigan Women in Communities Outside of Flint

Objective

To determine whether Black women in Michigan communities outside of Flint were more likely than women in other racial and ethnic groups to report negative emotional reactions to the Flint Water Crisis, an ongoing public health disaster that has been widely attributed to anti-Black structural racism.

Methods

Data were from a 2020 survey of Michigan women aged 18-45 in communities outside of Flint (N=888). We used logistic regression models to examine racial and ethnic differences in the odds of negative emotional reactions to the Flint Water Crisis.

Results

Compared with Black women, White women had lower odds of feeling scared (odds ratio [OR]=0.58; 95% CI, 0.40-0.84), hopeless (OR=0.53; 95% CI, 0.38-0.74), tired (OR=0.45; 95% CI, 0.32-0.64), and numb (OR=0.52; 95% CI, 0.35-0.75) when thinking about the water crisis. There were no differences between Black and Hispanic women, whereas women of other races or ethnicities had lower odds than Black women of feeling numb (OR=0.32; 95% CI, 0.14-0.72).

Conclusions

The Flint Water Crisis was a racialized stressor, with potential implications for mental health inequities among Michigan women who were not directly affected by the crisis.

Influence of pipe materials on in-building disinfection of P. aeruginosa and A. baumannii in simulated hot water plumbing

A framework is needed to account for interactive effects of plumbing materials and disinfectants on opportunistic pathogens (OPs) in building water systems. Here we evaluated free chlorine, monochloramine, chlorine dioxide, and copper-silver ionization (CSI) for controlling Pseudomonas aeruginosa and Acinetobacter baumannii as two representative OPs that colonize hot water plumbing, in tests using polyvinylchloride (PVC), copper-PVC, and iron-PVC convectively-mixed pipe reactors (CMPRs). Pipe materials vulnerable to corrosion (i.e., iron and copper) altered the pH, dissolved oxygen, and disinfectant levels in a manner that influenced growth trends of the two OPs and total bacteria. P. aeruginosa grew well in PVC CMPRs, poorly in iron-PVC CMPRs, and was best controlled by CSI disinfection, whereas A. baumannii showed the opposite trend for pipe material and was better controlled by chlorine and chlorine dioxide. Various scenarios were identified in which pipe material and disinfectant can interact to either hinder or accelerate growth of OPs, illustrating the difficulties of controlling OPs in portions of plumbing systems experiencing warm, stagnant water.

Legionellosis on the rise: A scoping review of sporadic, community-acquired incidence in the United States

Over the past two decades, the incidence of legionellosis has been steadily increasing in the United States though there is noclear explanation for the main factors driving the increase. While legionellosis is the leading cause of waterborne outbreaks in the US, most cases are sporadic and acquired in community settings where the environmental source is never identified. This scoping review aimed to summarise the drivers of infections in the USA and determine the magnitude of impact each potential driver may have. A total of 1,738 titles were screened, and 18 articles were identified that met the inclusion criteria. Strong evidence was found for precipitation as a major driver, and both temperature and relative humidity were found to be moderate drivers of incidence. Increased testing and improved diagnostic methods were classified as moderate drivers, and the ageing U.S. population was a minor driver of increasing incidence. Racial and socioeconomic inequities and water and housing infrastructure were found to be potential factors explaining the increasing incidence though they were largely understudied in the context of non-outbreak cases. Understanding the complex relationships between environmental, infrastructure, and population factors driving legionellosis incidence is important to optimise mitigation strategies and public policy.

Tap water as the source of a Legionnaires' disease outbreak spread to several residential buildings and one hospital, Finland, 2020 to 2021

In Finland, all microbiology laboratories notify Legionella findings and physicians notify Legionnaires' disease (LD) cases to the National Infectious Disease Register. All cases are interviewed, and water samples obtained from potential places of exposure. Legionella isolates from humans and water are compared by whole genome sequencing (WGS). In March 2021, Legionella pneumophila serogroup 1 (Lp 1) pneumonia cases increased in one Finnish city (120,000 inhabitants) where single LD cases are detected annually. We identified 12 LD cases, nine living in different residential buildings and three nosocomial, linked by identical human and/or water isolates. Three of these cases were from January 2020, October 2020 and February 2021 and identified retrospectively. Eleven were diagnosed by urinary antigen test, 10 by PCR and five by culture; age ranged between 52 and 85 years, and 10 had underlying diseases. Nine of 12 homes of LD cases and 15 of 26 water samples from the hospital were positive for Lp 1, with concentrations up to 640,000 cfu/L. Water samples from regional storage tanks were negative. Positivity in homes and the hospital suggested inadequate maintenance measures. Enhanced surveillance combined with WGS was crucial in detecting this unusual LD outbreak related to domestic and hospital water systems.

Did a Nocebo Effect Contribute to the Rise in Special Education Enrollment Following the Flint, Michigan Water Crisis?

Background

Exposure to waterborne lead during the Flint Water Crisis during April 2014-October 2015 is believed to have caused increased special education enrollment in Flint children.

Method

This retrospective population-based cohort study utilized de-identified data for children under six years of age who had their blood lead tested during 2011 to 2019, and special education outcomes data for children enrolled in public schools for corresponding academic years (2011-12 to 2019-20) in Flint, Detroit (control city) and the State of Michigan. Trends in the following crisis-related covariates were also evaluated: waterborne contaminants, poverty, nutrition, city governance, school district policies, negative community expectations, media coverage and social media interactions.

Results

Between 2011 and 2019, including the 2014-15 crisis period, the incidence of elevated blood lead in Flint children (≥ 5µg/dL) was always at least 47% lower than in the control city of Detroit (p < .0001) and was also never significantly higher than that for all children tested in Michigan (p = 0.33). Nonetheless, special education enrollment in Flint spiked relative to Detroit and Michigan (p < .0001). There is actually an inverse relationship between childhood blood lead and special education enrollment in Flint.

Conclusion

This study failed to confirm any positive association between actual childhood blood lead levels and special education enrollment in Flint. Negative psychological effects associated with media predictions of brain damage could have created a self-fulfilling prophecy via a nocebo effect. The findings demonstrate a need for improved media coverage of complex events like the Flint Water Crisis.

Biofilm Control in Flow-Through Systems Using Polyvalent Phages Delivered by Peptide-Modified M13 Coliphages with Enhanced Polysaccharide Affinity

Eradication of biofilms that may harbor pathogens in water distribution systems is an elusive goal due to limited penetration of residual disinfectants. Here, we explore the use of engineered filamentous coliphage M13 for enhanced biofilm affinity and precise delivery of lytic polyvalent phages (i.e., broad-host-range phages lysing multiple host strains after infection). To promote biofilm attachment, we modified the M13 major coat protein (pVIII) by inserting a peptide sequence with high affinity for Pseudomonas aeruginosa (P. aeruginosa) extracellular polysaccharides (commonly present on the surface of biofilms in natural and engineered systems). Additionally, we engineered the M13 tail fiber protein (pIII) to contain a peptide sequence capable of binding a specific polyvalent lytic phage. The modified M13 had 102- and 5-fold higher affinity for P. aeruginosa-dominated mixed-species biofilms than wildtype M13 and unconjugated polyvalent phage, respectively. When applied to a simulated water distribution system, the resulting phage conjugates achieved targeted phage delivery to the biofilm and were more effective than polyvalent phages alone in reducing live bacterial biomass (84 vs 34%) and biofilm surface coverage (81 vs 22%). Biofilm regrowth was also mitigated as high phage concentrations induced residual bacteria to downregulate genes associated with quorum sensing and extracellular polymeric substance secretion. Overall, we demonstrate that engineered M13 can enable more accurate delivery of polyvalent phages to biofilms in flow-through systems for enhanced biofilm control.

The drinking water crises of Flint and Havelock North: a failure of public health risk management

Between 2014 and 2016, there were two severe community water system (CWS) failures in Flint, Michigan (MI), USA and Havelock North, Hawkes Bay, New Zealand. These events had profound implications for public health in their respective countries. While the nature of both crises was different, certain aspects of the failings were strikingly similar. These included: failure of authorities to protect the integrity of their source water, 'wait-and-see approach' to address problems if and when they occurred, negligent approach to regulatory oversight and responsibility, substandard facilities and lack of knowledge and training of staff, failure of consultants and advisory services engaged by suppliers, and failure of government agencies to enforce regulations. The lessons from both incidents must be learned, or similar tragic events are likely to reoccur. The six principles identified in the Government Inquiry into the Havelock North outbreak are an essential first step. The next step is to implement them throughout the drinking water sector.

An online flow-imaging particle counter and conventional water quality sensors detect drinking water contamination in the presence of normal water quality fluctuations

Contamination detection in drinking water is crucial for water utilities in terms of public health; however, current online water quality sensors can be unresponsive to various possible contaminants consisting of particulate and dissolved content or require a constant supply of reagents and sample preparation. We used a two-line test environment connected to a drinking water distribution system with flow-imaging particle counters and conventional sensors to assess their responses to the injection of contaminants into one line, including stormwater, treated wastewater, wastewater, well water, and Escherichia coli, while simultaneously measuring responses to normal water quality fluctuations in the other line. These water quality fluctuations were detected with all of the conventional sensors (except conductivity) and with 3 out of 5 of the size- and shape-derived particle classes of the flow-imaging particle counter. The flow-imaging particle counter was able to detect all of the studied contaminants, e.g. municipal wastewater at 0.001% (v/v), while the oxidation-reduction potential sensor outperformed other conventional sensors, detecting the same wastewater at 0.03% (v/v). The presence of particles less than 1 µm in size was shown to be a generic parameter for the detection of particulates present in the studied contaminants; however, they manifested a considerable response to fluctuations which led to lower relative response to contaminants in comparison to larger particles. The particle size and class distributions of contaminants were different from those of drinking water, and thus monitoring particles larger than 1 µm or specific particle classes of flow-imaging particle counter, which are substantially more abundant in contaminated water than in pure drinking water, can improve the detection of contamination events. Water utilities could optimize contamination detection by selecting water quality parameters with a minimal response to quality fluctuations and/or a high relative response to contaminants.

Overview of the Clinical and Molecular Features of Legionella Pneumophila: Focus on Novel Surveillance and Diagnostic Strategies

Legionella pneumophila (L. pneumophila) is one of the most threatening nosocomial pathogens. The implementation of novel and more effective surveillance and diagnostic strategies is mandatory to prevent the occurrence of legionellosis outbreaks in hospital environments. On these bases, the present review is aimed to describe the main clinical and molecular features of L. pneumophila focusing attention on the latest findings on drug resistance mechanisms. In addition, a detailed description of the current guidelines for the disinfection and surveillance of the water systems is also provided. Finally, the diagnostic strategies available for the detection of Legionella spp. were critically reviewed, paying the attention to the description of the culture, serological and molecular methods as well as on the novel high-sensitive nucleic acid amplification systems, such as droplet digital PCR.

Variable Legionella Response to Building Occupancy Patterns and Precautionary Flushing

When stay-at-home orders were issued to slow the spread of COVID-19, building occupancy (and water demand) was drastically decreased in many buildings. There was concern that widespread low water demand may cause unprecedented Legionella occurrence and Legionnaires’ disease incidence. In lieu of evidenced-based guidance, many people flushed their water systems as a preventative measure, using highly variable practices. Here, we present field-scale research from a building before, during, and after periods of low occupancy, and controlled stagnation experiments. We document no change, a > 4-log increase, and a > 1.5-log decrease of L. pneumophila during 3- to 7-week periods of low water demand. L. pneumophila increased by > 1-log after precautionary flushing prior to reoccupancy, which was repeated in controlled boiler flushing experiments. These results demonstrate that the impact of low water demand (colloquially called stagnation) is not as straight forward as is generally assumed, and that some flushing practices have potential unintended consequences. In particular, stagnation must be considered in context with other Legionella growth factors like temperature and flow profiles. Boiler flushing practices that dramatically increase the flow rate and rapidly deplete boiler temperature may mobilize Legionella present in biofilms and sediment.

Tenets of a holistic approach to drinking water-associated pathogen research, management, and communication

In recent years, drinking water-associated pathogens that can cause infections in immunocompromised or otherwise susceptible individuals (henceforth referred to as DWPI), sometimes referred to as opportunistic pathogens or opportunistic premise plumbing pathogens, have received considerable attention. DWPI research has largely been conducted by experts focusing on specific microorganisms or within silos of expertise. The resulting mitigation approaches optimized for a single microorganism may have unintended consequences and trade-offs for other DWPI or other interests (e.g., energy costs and conservation). For example, the ecological and epidemiological issues characteristic of Legionella pneumophila diverge from those relevant for Mycobacterium avium and other nontuberculous mycobacteria. Recent advances in understanding DWPI as part of a complex microbial ecosystem inhabiting drinking water systems continues to reveal additional challenges: namely, how can all microorganisms of concern be managed simultaneously? In order to protect public health, we must take a more holistic approach in all aspects of the field, including basic research, monitoring methods, risk-based mitigation techniques, and policy. A holistic approach will (i) target multiple microorganisms simultaneously, (ii) involve experts across several disciplines, and (iii) communicate results across disciplines and more broadly, proactively addressing source water-to-customer system management.

Are there excess fetal deaths attributable to waterborne lead exposure during the Flint Water Crisis? Evidence from bio-kinetic model predictions and Vital Records

BACKGROUND

Flint, Michigan had elevated water lead (Pb) levels during the 2014-15 Flint Water Crisis (FWC) and reports claim the exposures caused excess fetal deaths.

OBJECTIVE

To model the likelihood of excess fetal deaths occurring from FWC lead exposure and compare results to Vital Records.

METHODS

We used an established bio-kinetic model to predict relative blood lead trends in pregnant women from characteristic exposure to 90th percentile water lead levels (WLLs), and another established model to then estimate characteristic miscarriage (<20 gestation weeks) odds ratios (OR) in Flint (2011-17). For comparison, we made similar predictions for exposures during (1) Washington DC's worst water lead crisis year (2001), (2) Flint "Resident Zero" home with anomalously high WLLs, and (3) 19th century lead-based abortifacients. Data on stillbirths (≥20 gestation weeks) and total fertility rates were obtained from the State of Michigan.

RESULTS

The models predicted that pregnant women drinking water with representative 90th percentile WLLs had a miscarriage OR during the worst FWC period (June-August 2014) of 1.21 (95% CI = 1.02,1.60), versus 1.66 (95% CI = 1.07, 3.56) during a time of high water lead 3 years before the FWC and 1.00 (95% CI = 1.00, 1.01) post-FWC. The corresponding predicted OR in late-2001 for Washington D.C. when higher fetal death rates were statistically associated with very high WLLs was 3.01 (95% CI = 1.16, 16.23). No apparent differences were revealed in overall and race-specific stillbirth rates before, during, or after the FWC. Total fertility rates dropped 6.8% during the FWC (April 2014-October 2015 versus April 2012-October 2013), but this is now revealed to be within the normal annual variation (-9.4% to +15%) observed post-FWC when residents were protected from water lead exposure.

SIGNIFICANCE

Neither model simulations nor Vital Records data are consistent with the hypothesis that there was an uptick in fetal deaths or decreased fertility attributable to water lead exposure during the FWC.

A review of legionnaires' disease and public water systems - Scientific considerations, uncertainties and recommendations

Legionella is an opportunistic premise plumbing pathogen and causative agent of a severe pneumonia called Legionnaires' Disease (LD). Cases of LD have been on the rise in the U.S. and globally. Although Legionella was first identified 45 years ago, it remains an 'emerging pathogen." Legionella is part of the normal ecology of a public water system and is frequently detected in regulatory-compliant drinking water. Drinking water utilities, regulators and public health alike are increasingly required to have a productive understanding of the evolving issues and complex discussions of the contribution of the public water utility to Legionella exposure and LD risk. This review provides a brief overview of scientific considerations important for understanding this complex topic, a review of findings from investigations of public water and LD, including data gaps, and recommendations for professionals interested in investigating public water utilities. Although the current literature is inconclusive in identifying a public water utility as a sole source of an LD outbreak, the evidence is clear that minimizing growth of Legionella in public water utilities through proper maintenance and sustained disinfectant residuals, throughout all sections of the water utility, will lead to a less conducive environment for growth of the bacteria in the system and the buildings they serve.

Legionella Occurrence beyond Cooling Towers and Premise Plumbing

Legionella is an environmental pathogen that is responsible for respiratory disease and is a common causative agent of water-related outbreaks. Due to their ability to survive in a broad range of environments, transmission of legionellosis is possible from a variety of sources. Unfortunately, a disproportionate amount of research that is devoted to studying the occurrence of Legionella in environmental reservoirs is aimed toward cooling towers and premise plumbing. As confirmed transmission of Legionella has been linked to many other sources, an over-emphasis on the most common sources may be detrimental to increasing understanding of the spread of legionellosis. This review aims to address this issue by cataloguing studies which have examined the occurrence of Legionella in less commonly investigated environments. By summarizing and discussing reports of Legionella in fresh water, ground water, saltwater, and distribution system drinking water, future environmental and public health researchers will have a resource to aid in investigating these pathogens in relevant sources.

The control of red water occurrence and opportunistic pathogens risks in drinking water distribution systems: A review

Many problems in drinking water distribution systems (DWDSs) are caused by microbe, such as biofilm formation, biocorrosion and opportunistic pathogens growth. More iron release from corrosion scales may induce red water. Biofilm played great roles on the corrosion. The iron-oxidizing bacteria (IOB) promoted corrosion. However, when iron-reducing bacteria (IRB) and nitrate-reducing bacteria (NRB) became the main bacteria in biofilm, they could induce iron redox cycling in corrosion process. This process enhanced the precipitation of iron oxides and formation of more Fe₃O₄ in corrosion scales, which inhibited corrosion effectively. Therefore, the IRB and NRB in the biofilm can reduce iron release and red water occurrence. Moreover, there are many opportunistic pathogens in biofilm of DWDSs. The opportunistic pathogens growth in DWDSs related to the bacterial community changes due to the effects of micropollutants. Micropollutants increased the number of bacteria with antibiotic resistance genes (ARGs). Furthermore, extracellular polymeric substances (EPS) production was increased by the antibiotic resistant bacteria, leading to greater bacterial aggregation and adsorption, increasing the chlorine-resistance capability, which was responsible for the enhancement of the particle-associated opportunistic pathogens in DWDSs. Moreover, O₃-biological activated carbon filtration-UV-Cl₂ treatment could be used to control the iron release, red water occurrence and opportunistic pathogens growth in DWDSs.

Citizen science chlorine surveillance during the Flint, Michigan federal water emergency

Rising incidence of waterborne diseases including Legionellosis linked to low chlorine residuals in buildings and the availability of inexpensive testing options, create an opportunity for citizen science chorine monitoring to complement sampling done by water utilities. University researchers and Flint residents coordinated a citizen science chlorine surveillance campaign in Flint, Michigan in 2015-19, that helped expose the nature of two deadly Legionnaires Disease outbreaks in 2014-2015 during the Flint Water Crisis and progress of system recovery during the Federal emergency. Results obtained with an inexpensive color wheel were in agreement with a digital colorimeter (R² =0.99; p = 2.81 × 10^-21) at 15 sites geographically distributed across Flint. Blinded tests revealed good agreement between official (n = 2051) and citizen (n = 654) data in terms of determining whether regulatory guidelines for chlorine were met, but a discovery that the citizen data were statistically lower than the city's (p<0.00001) especially in warm summer months led to recommendations for increased flushing of service lines before measurements. This work suggests that expanded citizen surveillance of chlorine, site specific flushing advice, and guidance on decisions about water heater set point could help consumers reduce Legionella risks in their homes. Citizen science initiatives for chlorine monitoring offer a unique opportunity for mutually beneficial collaborations between consumers and utilities to reduce the main source of waterborne disease in developed countries.

Electrochemical Disinfection in Water and Wastewater Treatment: Identifying Impacts of Water Quality and Operating Conditions on Performance

Electrochemical disinfection-a method in which chemical oxidants are generated in situ via redox reactions on the surface of an electrode-has attracted increased attention in recent years as an alternative to traditional chemical dosing disinfection methods. Because electrochemical disinfection does not entail the transport and storage of hazardous materials and can be scaled across centralized and distributed treatment contexts, it shows promise for use both in resource limited settings and as a supplement for aging centralized systems. In this Critical Review, we explore the significance of treatment context, oxidant selection, and operating practice on electrochemical disinfection system performance. We analyze the impacts of water composition on oxidant demand and required disinfectant dose across drinking water, centralized wastewater, and distributed wastewater treatment contexts for both free chlorine- and hydroxyl-radical-based systems. Drivers of energy consumption during oxidant generation are identified, and the energetic performance of experimentally reported electrochemical disinfection systems are evaluated against optimal modeled performance. We also highlight promising applications and operational strategies for electrochemical disinfection and propose reporting standards for future work.

Critical Review: Propensity of Premise Plumbing Pipe Materials to Enhance or Diminish Growth of Legionella and Other Opportunistic Pathogens

Growth of Legionella pneumophila and other opportunistic pathogens (OPs) in drinking water premise plumbing poses an increasing public health concern. Premise plumbing is constructed of a variety of materials, creating complex environments that vary chemically, microbiologically, spatially, and temporally in a manner likely to influence survival and growth of OPs. Here we systematically review the literature to critically examine the varied effects of common metallic (copper, iron) and plastic (PVC, cross-linked polyethylene (PEX)) pipe materials on factors influencing OP growth in drinking water, including nutrient availability, disinfectant levels, and the composition of the broader microbiome. Plastic pipes can leach organic carbon, but demonstrate a lower disinfectant demand and fewer water chemistry interactions. Iron pipes may provide OPs with nutrients directly or indirectly, exhibiting a high disinfectant demand and potential to form scales with high surface areas suitable for biofilm colonization. While copper pipes are known for their antimicrobial properties, evidence of their efficacy for OP control is inconsistent. Under some circumstances, copper's interactions with premise plumbing water chemistry and resident microbes can encourage growth of OPs. Plumbing design, configuration, and operation can be manipulated to control such interactions and health outcomes. Influences of pipe materials on OP physiology should also be considered, including the possibility of influencing virulence and antibiotic resistance. In conclusion, all known pipe materials have a potential to either stimulate or inhibit OP growth, depending on the circumstances. This review delineates some of these circumstances and informs future research and guidance towards effective deployment of pipe materials for control of OPs.

Excess Pneumonia Mortality During a 2014-2015 Legionnaires' Disease Outbreak in Genesee County, Michigan

BACKGROUND

From June 2014 to October 2015, the Michigan Department of Health and Human Services reported an outbreak of 90 cases of Legionnaires' disease, including 10 deaths, in Genesee County, Michigan. As Legionnaires' disease is not routinely tested for as a cause of community-acquired pneumonia, we hypothesized that the size of the outbreak was underestimated.

METHODS

We used Centers for Disease Control and Prevention (CDC) Wide-ranging ONline Data for Epidemiologic Research data to compare pneumonia mortality in Genesee to similar counties from 2011 to 2017. We used data from the Genesee County Vital Records Division to assess geographic overlap of pneumonia mortality with reported Legionnaires disease cases by census tract.

RESULTS

We estimated 70.0 excess pneumonia deaths (90% uncertainty interval: 36-103) in Genesee County during the outbreak. Areas of high pneumonia mortality overlapped with those with high Legionnaires' disease incidence.

CONCLUSIONS

These findings are consistent with the hypothesis that the Legionnaires' disease outbreak was larger than reported. Earlier outbreak detection and response may have facilitated identification of additional cases.

Molecular detection of opportunistic pathogens and insights into microbial diversity in private well water and premise plumbing

Private well water systems in rural areas that are improperly maintained will result in poor drinking water quality, loss of water supply, and pose human health risk. The purpose of this study was to investigate the occurrence of fecal indicator bacteria (FIB) and opportunistic pathogens in private well water in rural areas surrounding New Orleans, Louisiana. Our results confirmed the ubiquitous nature of Legionella (86.7%) and mycobacteria (68.1%) in private well water in the study area, with gene concentration ranged from 0.60 to 5.53 and 0.67 to 5.95 Log₁₀ of GC/100 mL, respectively. Naegleria fowleri target sequence was detected in 16.8% and Escherichia coli was detected in 43.4% of the water samples. Total coliform, as well as Legionella and mycobacteria genetic markers' concentrations were significantly reduced by 3-minute flushing. Next-generation sequencing (NGS) data indicated that the abundance of bacterial species was significantly increased in water collected in kitchens compared with samples from wells directly. This study provided integrated knowledge on the persistence of pathogenic organisms in private well water. Further study is needed to explore the presence of clinical species of those opportunistic pathogens in private well water systems to elucidate the health risk.

Chlorine Disinfection of Legionella spp., L. pneumophila, and Acanthamoeba under Warm Water Premise Plumbing Conditions

Premise plumbing conditions can contribute to low chlorine or chloramine disinfectant residuals and reactions that encourage opportunistic pathogen growth and create risk of Legionnaires' Disease outbreaks. This bench-scale study investigated the growth of Legionella spp. and Acanthamoeba in direct contact with premise plumbing materials-glass-only control, cross-linked polyethylene (PEX) pipe, magnesium anode rods, iron pipe, iron oxide, pH 10, or a combination of factors. Simulated glass water heaters (SGWHs) were colonized by Legionella pneumophila and exposed to a sequence of 0, 0.1, 0.25, and 0.5 mg/L chlorine or chloramine, at two levels of total organic carbon (TOC), over 8 weeks. Legionella pneumophila thrived in the presence of the magnesium anode by itself and or combination with other factors. In most cases, 0.5 mg/L Cl2 caused a significant rapid reduction of L. pneumophila, Legionella spp., or total bacteria (16S rRNA) gene copy numbers, but at higher TOC (>1.0 mg C/L), a chlorine residual of 0.5 mg/L Cl2 was not effective. Notably, Acanthamoeba was not significantly reduced by the 0.5 mg/L chlorine dose.

Interactive Effects of Copper Pipe, Stagnation, Corrosion Control, and Disinfectant Residual Influenced Reduction of Legionella pneumophila during Simulations of the Flint Water Crisis

Flint, MI experienced two outbreaks of Legionnaires' Disease (LD) during the summers of 2014 and 2015, coinciding with use of Flint River as a drinking water source without corrosion control. Using simulated distribution systems (SDSs) followed by stagnant simulated premise (i.e., building) plumbing reactors (SPPRs) containing cross-linked polyethylene (PEX) or copper pipe, we reproduced trends in water chemistry and Legionella proliferation observed in the field when Flint River versus Detroit water were used before, during, and after the outbreak. Specifically, due to high chlorine demand in the SDSs, SPPRs with treated Flint River water were chlorine deficient and had elevated L. pneumophila numbers in the PEX condition. SPPRs with Detroit water, which had lower chlorine demand and higher residual chlorine, lost all culturable L. pneumophila within two months. L. pneumophila also diminished more rapidly with time in Flint River SPPRs with copper pipe, presumably due to the bacteriostatic properties of elevated copper concentrations caused by lack of corrosion control and stagnation. This study confirms hypothesized mechanisms by which the switch in water chemistry, pipe materials, and different flow patterns in Flint premise plumbing may have contributed to observed LD outbreak patterns.

Improving state-level emergency well disinfection strategies in the United States

After flooding events, well users are encouraged to disinfect their private wells. However, well disinfection strategies are not consistently applied or proven effective. This study examines the science-based evidence that disinfection procedures reduce microbial loading in well water; reviews inclusion of disinfection principles in state-level emergency protocols; and explores research gaps potentially hindering disinfection efficacy. Emergency well disinfection protocols from 34 states were reviewed based on instructions for creating chlorine solutions; circulating chlorine solutions throughout the distribution system; achieving effective CT disinfection (chlorine dose*contact time); and post-disinfection guidance. Many protocols were missing key information about fundamentals of disinfection. Only two protocols instructed well users to verify chlorine residuals and three protocols instructed users to measure water pH. Most protocols recommended that high chlorine doses be introduced into the well, circulated throughout the system, and stagnated for several hours. A CT value estimated to inactivate at least 99.9% (3-log removal) of Cryptosporidium (255 mg-hr/L) was predicted to be achieved by 72.7% of protocols, and estimated CT values ranged from 35 to 16,327 mg-hr/L. Two research gaps identified were determining whether chlorine doses should differ based on well water chemistries and evaluating the appropriate chlorine dose that should be recommended for inactivating pathogens. This effort underscores a need for consistent, evidence-based messaging in emergency well disinfection protocols.

The Impact of the Flint Water Crisis on Fertility

Flint switched its public water source in April 2014, increasing exposure to lead and other contaminants. We compare the change in the fertility rate and in health at birth in Flint before and after the water switch to the changes in other cities in Michigan. We find that Flint fertility rates decreased by 12 % and that overall health at birth decreased. This effect on health at birth is a function of two countervailing mechanisms: (1) negative selection of less healthy embryos and fetuses not surviving (raising the average health of survivors), and (2) those who survived being scarred (decreasing average health). We untangle this to find a net of selection scarring effect of 5.4 % decrease in birth weight. Because of long-term effects of in utero exposure, these effects are likely lower bounds on the overall effects of this exposure.

Residential water heater cleaning and occurrence of Legionella in Flint, MI

After the Federal emergency in Flint, MI was declared in early 2016 in response to elevated lead-in-water and incidence of Legionnaires' disease, concerns arose that contaminants in residential water heaters could continue to contribute to poor quality tap water. Here, a comprehensive field survey of residential water heaters (n = 30) and associated water quality was conducted and the subsequent effects of an aggressive manual water heater clean-out was determined, including draining the tank and removing sediments via brushing and flushing. Before cleaning, inorganics accumulated in the tank sediments did not serve as a source of metals measured at hot water outlets. After cleaning, hardness- (calcium, magnesium, silica) and corrosion-associated inorganics (lead, iron, copper, aluminum, zinc) decreased by 64% in samples from sediment cleanout drain valves. Culturable L. pneumophila was only detected in 1 home (3.3%) prior to cleaning and 2 homes (6.7%) after cleaning, thus quantitative polymerase chain reaction was used to quantify potential effects on unculturable strains despite the limitation of differentiating live and dead cells. After the cleaning protocol, Legionella spp. and L. pneumophila gene numbers decreased or remained non-detectable in 83% and 98% of samples, respectively. Homes with less than 0.4 mg/L influent free chlorine tended to have quantifiable Legionella spp. gene numbers in water entering the home and had elevated L. pneumophila and Legionella spp. gene numbers throughout the home plumbing. Also, Legionella spp. and L. pneumophila gene numbers were highest for water heaters set at or below ∼42 °C and significantly decreased >51 °C, consistent with Legionella's preferred temperature range. Examination of the only home that had culturable L. pneumophila both before and after the cleaning protocol revealed that the organism was culturable from several sample locations throughout the home, including in water representative of the water main. Notably, the home was located in close proximity to McLaren Hospital, where an outbreak of Legionnaires disease was reported, and the water heater had a setpoint within the Legionella growth range of 44.2 °C. Considering that other factors were more strongly associated with Legionella occurrence and water heater sediment was not detectably mobilizing to tap water, it was concluded that water heater cleaning had some benefits, but was not an overarching factor contributing to possible human health risks.

Spatiotemporal trends of recovery from lead contamination in Flint, MI as revealed by crowdsourced water sampling

In the aftermath of the lead contamination crisis that plagued the water system in Flint, MI, more than 35,000 water samples were collected from the city's premises. The majority of these samples (>85%) were collected through a voluntary crowdsourced sampling campaign. The samples were analyzed for lead and copper concentrations by the Michigan Department of Environmental Quality (MDEQ). In this study, the crowdsourced sampling data was analyzed by means of spatial autocorrelation analysis to reveal the locations of statistically significant hotspot regions of high water lead levels (WLLs), and to track the spatiotemporal evolution of WLLs as the system recovered from lead contamination. The results showed that hotspot regions that experienced high WLLs were consistent with the areas where lead service line (LSL) density was the highest. Additionally, galvanized service lines and other lead-containing plumbing components could have also contributed to lead release in hotspot regions. The temporal trend exhibited by the crowdsourced sampling data did not reflect a consistent decrease in WLLs despite the interventions implemented by MDEQ and EPA. Instead, sampled WLLs remained high for several months after boosting the orthophosphate dose and launching a city-wide residential flushing campaign. The findings of this study suggest that this could be partially attributed to disproportionate sampling from premises in hotspot regions of high WLLs and LSL density.

Multiple Sources of the Outbreak of Legionnaires' Disease in Genesee County, Michigan, in 2014 and 2015

BACKGROUND

A community-wide outbreak of Legionnaires' disease (LD) occurred in Genesee County, Michigan, in 2014 and 2015. Previous reports about the outbreak are conflicting and have associated the outbreak with a change of water source in the city of Flint and, alternatively, to a Flint hospital.

OBJECTIVE

The objective of this investigation was to independently identify relevant sources of Legionella pneumophila that likely resulted in the outbreak.

METHODS

An independent, retrospective investigation of the outbreak was conducted, making use of public health, health care, and environmental data and whole-genome multilocus sequence typing (wgMLST) of clinical and environmental isolates.

RESULTS

Strong evidence was found for a hospital-associated outbreak in both 2014 and 2015: a) 49% of cases had prior exposure to Flint hospital A, significantly higher than expected from Medicare admissions; b) hospital plumbing contained high levels of L. pneumophila; c) Legionella control measures in hospital plumbing aligned with subsidence of hospital A-associated cases; and d) wgMLST showed Legionella isolates from cases exposed to hospital A and from hospital plumbing to be highly similar. Multivariate analysis showed an increased risk of LD in 2014 for people residing in a home that received Flint water or was located in proximity to several Flint cooling towers.

DISCUSSION

This is the first LD outbreak in the United States with evidence for three sources (in 2014): a) exposure to hospital A, b) receiving Flint water at home, and c) residential proximity to cooling towers; however, for 2015, evidence points to hospital A only. Each source could be associated with only a proportion of cases. A focus on a single source may have delayed recognition and remediation of other significant sources of L. pneumophila. https://doi.org/10.1289/EHP5663.

Comparison of Whole-Genome Sequences of Legionella pneumophila in Tap Water and in Clinical Strains, Flint, Michigan, USA, 2016

During the water crisis in Flint, Michigan, USA (2014-2015), 2 outbreaks of Legionnaires' disease occurred in Genesee County, Michigan. We compared whole-genome sequences of 10 clinical Legionella pneumophila isolates submitted to a laboratory in Genesee County during the second outbreak with 103 water isolates collected the following year. We documented a genetically diverse range of L. pneumophila strains across clinical and water isolates. Isolates belonging to 1 clade (3 clinical isolates, 3 water isolates from a Flint hospital, 1 water isolate from a Flint residence, and the reference Paris strain) had a high degree of similarity (2-1,062 single-nucleotide polymorphisms), all L. pneumophila sequence type 1, serogroup 1. Serogroup 6 isolates belonging to sequence type 2518 were widespread in Flint hospital water samples but bore no resemblance to available clinical isolates. L. pneumophila strains in Flint tap water after the outbreaks were diverse and similar to some disease-causing strains.

Legionella: a reemerging pathogen

PURPOSE OF REVIEW

The present review summarizes new knowledge about Legionella epidemiology, clinical characteristics, community-associated and hospital-based outbreaks, molecular typing and molecular epidemiology, prevention, and detection in environmental and clinical specimens.

RECENT FINDINGS

The incidence of Legionnaire's disease is rising and the mortality rate remains high, particularly for immunocompromised patients. Extracorporeal membrane oxygenation may help support patients with severe respiratory failure. Fluoroquinolones and macrolides appear to be equally efficacious for treating Legionnaires' disease. Whole genome sequencing is an important tool for determining the source for Legionella infections and for understanding routes of transmission and mechanisms by which new pathogenic clones emerge. Real-time quantitative polymerase chain reaction testing of respiratory specimens may improve our ability to diagnose Legionnaire's disease. The frequency of viable but nonculturable organisms is quite high in some water systems but their role in causing clinical disease has not been defined.

SUMMARY

Legionellosis remains an important public health threat. To prevent these infections, staff of municipalities and large buildings must implement effective water system management programs that reduce Legionella growth and transmission and all Medicare-certified healthcare facilities must have water management policies. In addition, we need better methods for detecting Legionella in water systems and in clinical specimens to improve prevention strategies and clinical diagnosis.

Legionnaires Disease Surveillance in US Department of Veterans Affairs Medical Facilities and Assessment of Health Care Facility Association

IMPORTANCE

Legionnaires disease (LD) incidence is increasing in the United States. Health care facilities are a high-risk setting for transmission of Legionella bacteria from building water systems to occupants. However, the contribution of LD in health care facilities to national LD rates is not well characterized.

OBJECTIVES

To determine the burden of LD in US Department of Veterans Affairs (VA) patients and to assess the amount of LD with VA exposure.

DESIGN, SETTING, AND PARTICIPANTS

Retrospective cohort study of reported LD data in VA medical facilities in a national VA LD surveillance system from January 1, 2014, to December 31, 2016. The study population included total veteran enrollees and enrollees who used the VA health care system.

MAIN OUTCOMES AND MEASURES

The primary outcome was assessment of annual LD rates, categorized by VA and non-VA exposure. Legionnaires disease rates for cases with VA exposure were determined on both population and exposure potential levels. Rates by VA exposure potential were calculated using inpatient bed days of care, long-term care resident days, or outpatient encounters. In addition, types and amounts of LD diagnostic testing were calculated. Case and testing data were analyzed nationally and regionally.

RESULTS

There were 491 LD cases in the case report surveillance system from January 1, 2014, to December 31, 2016. Most cases (447 [91%]) had no VA exposure or only outpatient VA exposure. The remaining 44 cases had VA exposure from overnight stays. Total LD rates from January 1, 2014, to December 31, 2016, increased for all VA enrollees (from 1.5 to 2.0 per 100 000 enrollees; P = .04) and for users of VA health care (2.3 to 3.0 per 100 000 enrollees; P = .04). The LD rate for the subset who had no VA exposure also increased (0.90 to 1.47 per 100 000 enrollees; P < .001). In contrast, the LD rate for patients with VA overnight stay decreased on a population level (5.0 to 2.3 per 100 000 enrollees; P < .001) and an exposure level (0.31 to 0.15 per 100 000 enrollees; P < .001). Regionally, the eastern United States had the highest LD rates. The urine antigen test was the most used LD diagnostic method; 49 805 tests were performed in 2015-2016 with 335 positive results (0.67%).

CONCLUSIONS AND RELEVANCE

Data in the VA LD databases showed an increase in overall LD rates over the 3 years, driven by increases in rates of non-VA LD. Inpatient VA-associated LD rates decreased, suggesting that the VA's LD prevention efforts have contributed to improved patient safety.

Influence of secondary water supply systems on microbial community structure and opportunistic pathogen gene markers

Secondary water supply systems (SWSSs) refer to the in-building infrastructures (e.g., water storage tanks) used to supply water pressure beyond the main distribution systems. The purpose of this study was to investigate the influence of SWSSs on microbial community structure and the occurrence of opportunistic pathogens, the latter of which are an emerging public health concern. Higher numbers of bacterial 16S rRNA genes, Legionella and mycobacterial gene markers were found in public building taps served by SWSSs relative to the mains, regardless of the flushing practice (P < 0.05). In residential buildings, genes of L. pneumomhila, Acanthamoeba and Vermamoeba vermiformis were primarily detected in tanks and taps compared to the mains. Long water retention time, warm temperature and loss of disinfectant residuals promoted microbial growth and colonization of potential pathogens in SWSSs. Varied levels of microbial community shifts were found in different types of SWSSs during water transportation from the distribution main to taps, highlighting the critical role of SWSSs in shaping the drinking water microbiota. Overall, the results provided insight to factors that might aid in controlling pathogen proliferation in real-world water systems using SWSSs.

Quantitative Microbial Risk Assessment and Opportunist Waterborne Infections⁻Are There Too Many Gaps to Fill?

Quantitative microbial risk assessment (QMRA) is a relatively new approach in identifying health risks associated with the ubiquitous presence of pathogens and opportunists in the human environment. The methodology builds on experimental and meta-analytical data to identify measurable factors that contribute to, and can quantify, the likely extent of disease given a particular exposure. Early modelling was particularly focused on food-borne disease, and subsequently water-borne disease, with the emphasis focused on ingestion and its role in enteric disease. More recently, there has been a focus on translating these principles to opportunist waterborne infections (OWI) with primary focus on Legionella spp. Whereas dose and susceptibility are well documented via the ingestion route of exposure there is considerably less certainty regarding both factors when understanding Legionella spp. and other OWI. Many OWI can arise through numerous routes of transmission with greatly differing disease presentations. Routes of Legionella spp. infection do not include ingestion, but rather aspiration and inhalation of contaminated water are the routes of exposure. The susceptible population for OWI is a vulnerable sub-set of the population unlike those associated with enteric disease pathogens. These variabilities in dose, exposure and susceptibility call in to question whether QMRA can be a useful tool in managing risks associated with OWI. Consideration of Legionella spp. as a well-documented subject of research calls into question whether QMRA of OWI is likely to be a useful tool in developing risk management strategies.