PLOS Water

Intermittent water supplies (IWS) serve >1 billion people globally and can transmit waterborne infections. How often and for how long supply is delivered varies between and within IWS systems. The UN Sustainable Development Goals target having water available when needed for >=12 hours/day or >=4 days/week but there are scarce data on how supply frequency/duration within IWS affect health outcomes. We conducted a matched study in Hubli-Dharwad, India, a city served partially by continuous water supply (CWS) since 2007 and partially by IWS. We enrolled 2220 CWS and 2218 IWS households matched on socioeconomics and sanitation. We compared diarrhea prevalence in children <5 years and typhoid fever incidence between households with different water supply characteristics using generalized linear models with robust standard errors and adjusting for socio-demographics and sanitation. Among IWS households, the median supply frequency was every 8 days (interquartile range [IQR]=7-8), and the median supply duration was 4 hours (IQR=3-5). IWS households had 36% higher prevalence of child diarrhea (prevalence ratio [PR]=1.36, 1.00-1.84) and 78% more typhoid fever cases (cumulative incidence ratio [CIR]=1.78, 1.05-3.02) than CWS households. IWS households meeting the UN criterion and those in the top quintiles of supply frequency and duration (receiving water once every 1-6 days or for 7-24 hours per supply cycle) had similar health outcomes as CWS households. IWS households below the UN criterion had higher diarrhea prevalence (PR=1.41, 1.03-1.93) and more typhoid fever cases (CIR=1.93, 1.15-3.22) than CWS households, as well as more typhoid fever cases than IWS households meeting the criterion (CIR=3.66, 1.37-9.79). IWS households in the bottom quintiles of supply frequency and duration (receiving water once every 9-15 days or for <=3 hours per supply cycle) had 45-72% higher child diarrhea prevalence and twice as many typhoid fever cases than CWS households (p-values<0.05). These findings support global efforts to implement CWS. Our results also highlight that increasing supply frequency and duration in IWS systems in the interim can deliver health benefits, and the UN criterion of having water available when needed improves health.

Background. Safely managed drinking-water monitoring under Sustainable Development Goal target 6.1 uses source-water quality, yet Escherichia coli is common in household drinking water in Bangladesh despite near-universal improved sources. We compared source and household point-of-use (POU) E. coli detection within households and estimated how the safely managed estimate changes if POU replaces source E. coli. Methods. Cross-sectional secondary analysis of the Bangladesh MICS 2025 water-quality subsample (February-June 2025; detection >=1 colony-forming unit/100 mL). We classified 5,944 households with readable paired results into four joint patterns and, exploratorily, examined POU detection among negative-source households and two-week diarrhoea in children under five with survey-weighted modified Poisson models. Results. E. coli was detected in 47.4% of source and 84.8% of POU samples; only 12.7% of households were negative at both. Among negative-source households, 75.8% had E. coli in household water, versus 94.7% with a detected source, persisting (33.3%) even direct from the source. The JMP-aligned safely managed estimate was 42.5% (95% CI 40.8-44.1); substituting POU for source E. coli gave 12.6% (11.4-13.8), not an SDG indicator estimate. The diarrhoea prevalence ratio for POU detection (1.04, 0.59-1.86) was too imprecise to interpret. In exploratory spatial analysis, POU detection clustered geographically (Moran's I 0.16 cluster level, 0.31 district level, both p<0.001) and was independently associated with lower elevation (odds ratio 0.62, 0.56-0.70) and longer travel time to healthcare (1.65, 1.29-2.12); five districts had complete detection among 84-94 households tested. Conclusions. Source and POU classifications differed substantially; the survey cannot show where or when contamination occurred. Contamination was spatially clustered, arguing against pure noise and pointing to districts for follow-up. The findings support evaluating standardised POU sampling as a complement to source-based monitoring, with targeted follow-up and cross-season, cross-country replication.

Wastewater-based epidemiology (WBE) has become a cornerstone of public health surveillance, yet routine regulatory monitoring remains largely focused on respiratory viruses and selecting antimicrobial resistant bacteria. Emerging foodborne parasites, such as Cyclospora cayetanensis, remain excluded from standard environmental surveillance panels despite increasing domestic outbreaks. This study presents a laboratory-based pilot protocol evaluating the feasibility of extracting and quantifying C. cayetanensis from urban wastewater across the Chicago metropolitan area. Using sample concentration via centrifugation and mechanical bead-beating, automated magnetic bead nucleic acid extraction, and digital PCR (dPCR), we demonstrate high-sensitivity detection in municipal influents and sewer nodes. These findings establish a proof-of-concept laboratory methodology to support the expansion of regulatory public health surveillance frameworks to include non-routine protozoan pathogens.

Essential for nutrient growth, due to intensive farming practices nitrate has become a common water contaminant in agricultural states. US nitrate regulations are designed to protect the health of newborns and infants, but have never been revised to consider potential harms of prenatal exposure. Recent evidence, however, suggests that exposure below the 10 mg/L regulatory limit may be associated with adverse birth outcomes. This current study examines whether first-trimester exposure below the regulatory limit is associated with adverse birth outcomes in Iowa (an intensive agricultural state). Finished drinking-water nitrate measurements from Iowa public water systems were linked to birth records. Nitrate measures were aggregated to a balanced county-quarter panel (1983 to 1988). Each pregnancy was assigned an average nitrate exposure over a 98-day first-trimester window. All births with a first trimester county-quarter nitrate measure >= 10 mg/L were excluded. Linear probability models with county-by-year and year-by-conception-quarter fixed effects, with standard errors clustered by county, estimated both uncorrected and Sidak corrected inference. The final analytic sample included 113,328 singleton births. Relative to lowest exposure category (0.1 mg/L or below), exposure to 5 mg/L or more nitrate was associated with a 1.04 percentage-point increase in the probability of preterm birth (CI = 0.24 to 1.83), a 13.5% relative increase, and associated with a 0.53 percentage-point increase in very preterm birth (CI = 0.08 to 0.97), a 46.2% relative increase. The statistical significance of both estimates persisted after correction for multiple tests. Exposure to > 0.1 mg/L and < 5 mg/L was not associated with any outcome. These preterm and very preterm birth associations were consistent across several sensitivity checks. Because nitrate concentrations between 5 to <10 mg/L comply with current rules, these findings warrant reassessing approaches to protect the health of pregnant women and their children.

Coastal waters often experience fecal contamination from human (e.g., septic systems, wastewater treatment catchments and outfalls) and non-human (e.g., wildlife, domesticated pets, and livestock) origins, posing human health risks through contaminated fisheries and recreational waters. Quantitative PCR (qPCR) methods can identify and quantify fecal origins for their management by targeting Bacteroides, a dominant group of gastrointestinal bacteria with high host specificity. This study identified major contributors and drivers of fecal contamination to Mobile Bay, Alabama, an urbanized estuary in the southern United States. We utilized a multi-species qPCR source tracking approach targeting total Bacteroides and human-, pig-, dog-, cow-, and fowl-associated Bacteroides. Water samples and environmental parameters were collected over one year from 13 sites that represent a range of potential fecal inputs common to coastal waters. Human-associated feces were a consistent major contributor to the system (positive in 82% of samples), with localized inputs from pig (wild or domestic) and dog. Freshwater discharge and nitrogen constituents were good predictors of Bacteroides concentrations in this system, while areas with impervious surfaces and developed land cover may be contributing elevated fecal indicator levels. The multi-species qPCR source tracking approach described in this study can be implemented in other watersheds to support the development of better detection, identification, and fecal management strategies for community health of coastal areas.

Background: The proportion of births occurring at healthcare facilities is rising globally, yet the birthing environment in healthcare facilities in low-income settings is often contaminated with bacterial pathogens, including antibiotic-resistant pathogens, that can lead to serious infections for newborns and their mothers. There is a need for effective strategies to reduce environmental contamination in healthcare facilities to reduce infection risks among facility-born neonates and their mothers. Methods: We designed the CLEAN (ChLorine to reduce Enteric and Antibiotic resistant infections in Neonates) cluster randomized controlled trial in western Kenya to evaluate the impact of a multi-component chlorination intervention on environmental contamination and maternal and neonatal infection risks. Thirty-six medium-sized public health facilities will be randomized in a 1:1 allocation ratio to receive a passive chlorination technology for water supply treatment paired with a reliable supply of chlorine-based disinfectant or status quo. Up to 22,500 mothers-neonate dyads will be enrolled and followed from birth through 28 days to collect symptoms of infection and mortality, with a subset of mother-neonate dyads selected for rectal swab collection to measure rectal colonization with sepsis-associated bacterial species. Environmental samples will be collected to measure bacterial pathogens on staff hands, high-touch surfaces, and in water supply. The primary objectives of the study are to evaluate the impact of the intervention on the following outcomes: (1) rectal carriage of bacterial pathogens one week post-birth among facility-born neonates and their mothers, (2) cumulative incidence in the first 7 days post-birth of possible serious bacterial infection among facility-born neonates, and (3) cumulative incidence in the first 7 days post-birth of symptoms of possible maternal sepsis. Discussion: This study will generate evidence on the effectiveness of a novel chlorination intervention to reduce healthcare associated infections, including antibiotic resistant infections, and improve maternal and neonatal survival. Trial registration: Clinical Trials NCT06824350. Registered 7 February 2025, https://clinicaltrials.gov/study/NCT06824350

Objectives: This study investigates public opinion regarding the use of wastewater and environmental surveillance for measles in South African urban centres across ethical, legal, and public health policy themes, and maps these opinions onto existing bioethical and legal precedents. Design: In-person field survey. Setting: Three metropolitan catchment areas in Gauteng Province, South Africa (City of Tshwane, City of Ekurhuleni, and City of Johannesburg). Participants: A sample of 100 adult community members residing or working within the selected sewer catchment areas. Primary outcome measures: Baseline wastewater and environmental surveillance awareness, target-specific acceptability, spatial monitoring preferences, data-sharing comfort, and legal/privacy perceptions. Results: Baseline awareness of WES was low (19%). Support was high for monitoring a range of biological and chemical targets using wastewater and environmental surveillance. However, acceptability was dependent on spatial scale: 83% supported macro-level city-wide monitoring, whereas support fell to 28% for localized sampling (individual homes and schools). Institutional trust in data handling was high among scientific and public health bodies. Conclusions: Public acceptability of WES for communicable diseases, particularly measles, in urban South Africa is high but conditional upon macro-level data aggregation (anonymity by aggregation) and governance by dedicated scientific entities. Given strong community support for measles surveillance and its alignment with the country bioethical and legal frameworks, the bioethical and legal requirements for this surveillance approach can be satisfied, paving the way for routine implementation of wastewater and environmental surveillance for communicable diseases.

Household tap waters harbor diverse microbial communities that can be highly variable in composition. While most microbes found in tap water are of limited clinical significance, nontuberculous mycobacteria (NTM), a group of bacteria commonly detected in household plumbing, pose an increasing threat to public health. Although exposure to tap water has been proposed as an important route of infection for mycobacterial pulmonary disease, it remains unclear how the amounts and types of NTM vary across homes within a given metropolitan area or even within individual homes between cold and hot tap water supplies. To address this knowledge gap, we used culture independent methods, namely 16S rRNA gene sequencing paired with quantitative PCR and mycobacterial-specific marker gene sequencing, to characterize the amounts and types of mycobacteria, including known pathogens, found in the source water, finished water, distribution system, and premise plumbing hot and cold tap waters across 16 homes in the same metropolitan area (Chicago, USA). Clinically relevant mycobacteria (Mycobacterium avium, M. xenopi, and M. mucogenicum/phocaicum) were frequently detected in both cold and hot tap waters, but their occurrence varied appreciably between homes receiving water from the same treatment facility. This high degree of variation in the detection of pathogenic NTM was associated with some of the measured water quality parameters, including turbidity levels, with more turbid waters being more likely to harbor pathogenic NTM, but much of the variation across tap water samples remained unexplained. The large amount of variation in the amounts and types of NTM, including those of clinically relevance, observed across households within the same water supply system highlights the need to better understand the ecology of NTM in premise plumbing to guide public health recommendations.

This study developed a streamlined, sensitive and rapid method for co-detection of low concentrations of Salmonella enterica, Shigella flexneri, Listeria monocytogenes, and pathogenic Escherichia coli from soil. First, autoclaved soil from Iowa with serial dilutions of bacteria to confirm individual species recovery rates on selective agar by qPCR under varying primary enrichment times was used. All pathogens were detected by qPCR of colonies recovered from replicate sterile soils spiked with 10^1 or greater bacteria within 5 hours of enrichment. Shiga toxin expressing E. coli (STEC) and L. monocytogenes were consistently co-recovered in autoclaved and natural soil, pathogen spiking concentration, and secondary enrichment time. S.enterica was consistently recovered at autoclaved and natural concentrations, while S. flexneri detection rates fluctuated. Twenty-three soil samples from Kenyan neighborhoods, with prior evidence of contamination, was compared to qPCR detection at each protocol stage: processing, primary enrichment, secondary enrichment, and selective colony isolation. Detection rates substantially increased for S. enterica, STEC and other pathogenic E. coli after enrichment, with optimal detection rates occurring after secondary enrichment. Testing colonies from selective agar resulted in high false negative rates, possibly reflecting competition from native soil microbiota that was absent in spiked sterile soil experiment. Evaluation of the method with other environmental sample types yielded consistent detection patterns. Evidence suggests a protocol including 24-hour primary enrichment, followed by 24-hour secondary enrichment, and qPCR testing of soil DNA at primary and secondary steps is a reproducible and more expedient method for co-detecting common Enterobacteriaceae and L. monocytogenes pathogens in soil.

Since the COVID-19 pandemic, wastewater-based surveillance (WBS) has emerged as a key approach to assess community-level health and the evolution of pathogens. To date, most established WBS systems focus on polymerase chain reaction (PCR) based detection and targeted sequencing of known pathogens because these approaches are well-accepted and include amplification of pathogen target sequences of interest thereby enabling lower limits of detection. Metagenomic next-generation sequencing (mNGS) is a promising approach to enable pathogen detection and surveillance beyond predefined pathogen lists, but its regular application to WBS has not been yet widely adopted because many key performance characteristics are not well-understood, including limit of detection (LOD) and false positive/negative rates. This paper describes a computational analysis to estimate the operational LOD of various sequencing approaches using a simplified model of a local wastewater (WW) system involving a military base. This paper also presents findings from two types of experiments: 1) laboratory-spiked, those for which Atlantibacter subterraneus (Asub) is introduced into real-world WW samples in a laboratory setting, and 2) system-spiked, those for which Asub is introduced at a source location of a real-world WW system. Findings indicate that mNGS detection performance varies with sequencing method and the data analysis process. In addition, findings indicate that site-specific method characterization should be used when implementing mNGS for WBS because sites can have different WW system configurations, background organisms and sequencing inhibitors.

Background: In coastal Bangladesh, saline drinking water has been linked to raised blood pressure. The 2025 Multiple Indicator Cluster Survey (MICS) measured electrical conductivity (EC), a salinity indicator, in source water, but its report gave no population counts or district estimates. Objectives: To estimate how many people live in households whose tested source has high EC, and to describe patterns by place, household characteristics, source type and arsenic. Methods. EC was measured in source water of 6,040 households in 64 districts, February to June. In 14.5% of households the tested source was not the main drinking-water source. Primary outcomes were EC above 1,500 and 3,000 microsiemen/cm, survey risk classes that are not health-based standards. Estimates were survey weighted; comparisons were observational. Results: EC exceeded 1,500 microsiemen/cm in 5.3% of households (95% CI 4.7 to 5.9), about 9.0 million people, including 1.8 million above 3,000 microsiemen/cm. Coastal-zone districts held 26% of households but 70% of those above 1,500 microsiemen/cm. Shares varied little by wealth or in households with young children or pregnant women. Nationally, deep tube wells more often had high EC because most are coastal. In the coastal zone, deep and shallow wells had similar shares (16.1% and 17.9%). After district adjustment, EC was about 18% lower in deep wells (geometric mean ratio 0.82, 0.73 to 0.92). Within upazilas (restricted sample) it was 0.93 (0.80 to 1.07). Arsenic above 10 ppb was more common where EC was high, but this link weakened after district adjustment. Conclusions: Millions of people live in households whose tested source has high EC, mostly in coastal and south-central districts. Deep wells had modestly lower EC after geographic adjustment, but the difference shrank within upazilas and depended on the handling of implausibly low readings. The findings support measuring EC alongside arsenic, with documented meter calibration.

Background: Population-based biomonitoring of contemporary-use pesticides remains limited in the United States, particularly in rural agricultural regions, and few studies have repeated measurements within the same individuals over time. Methods: We analyzed 28 urinary pesticide-related biomarkers among 600 adults from the population-based Survey of the Health of Wisconsin with archived urine collected during 2008-2016; 296 participants provided repeat urine and updated exposure information in 2025. Detection frequencies, co-detection, and within-person detection patterns were characterized. Generalized estimating equations were used for stacked, repeated-measures analyses of factors associated with detection of aminomethylphosphonic acid (AMPA), glyphosate, 2,4-dichlorophenoxyacetic acid (2,4-D), and any of these three. Prospective-only analyses evaluated more detailed agricultural and recent exposure measures. Results: Glyphosate, AMPA, and 2,4-D were detected in 7.7%, 6.2%, and 4.3% of retrospective specimens and 5.4%, 3.1%, and 4.1% of prospective specimens, respectively. Co-detection and persistent detection across the 9 to 17-year interval was rare. In repeated-measures models, greater fruit and vegetable intake, older age, and male sex were associated with higher 2,4-D detection. Lower household income was associated with lower AMPA detection, while afternoon/evening collection was associated with higher AMPA detection. In prospective analyses, working on field-crop agricultural land showed the strongest agricultural associations, particularly for 2,4-D and detection of any of the three pesticides. Associations were not seen with self-reported conventional versus organic produce consumption. Conclusions: Urinary pesticide detections were generally infrequent in this Wisconsin population. Diet and direct agricultural activities may be more informative exposure pathways than residing near cropland or private well drinking-water characteristics.

Summary Background: Wastewater and environmental surveillance (WES) enables community-level monitoring of infectious diseases. Most progress has focused on sewer-based surveillance, yet nearly half of the global population relies on non-sewered sanitation. In non-sewered settings, urban drainage channels have been used for poliovirus environmental surveillance, but their potential for a multi-pathogen WES with spatially defined catchments, and comparability to sewer-based surveillance, remains under-explored. Methods: Ten drainage channel sampling points with delineated micro-catchments (0.95-3.83 km2 with 12,885-44,146 people) were selected within Kampala. A total of 255 drainage channel and 54 wastewater treatment plant (WWTP) influent samples were collected during two campaigns in March and September-October 2025. A multi-target panel was quantified by digital PCR, including enteric viruses (Norovirus GI and GII, Rotavirus), respiratory viruses (SARS-CoV-2, Influenza A and B viruses, Respiratory Syncytial Virus (RSV)), non-O1/O139 Vibrio cholerae (V. cholerae), and Pepper Mild Mottle Virus (PMMoV) as a fecal indicator. Findings: Enteric viruses, non-O1/O139 V. cholerae, and PMMoV were consistently detected across all drainage channels and WWTP influents. Concentrations were generally lower in drainage than WWTP influents, except for non-O1/O139 V. cholerae. When normalized by PMMoV, concentrations across most drainage channels were comparable to WWTP influents, although comparability varied by target and location. Both concentrations and PMMoV-normalized concentrations varied across sampling locations. Trends between campaigns varied by pathogen target and were not explained by any single micro-catchment characteristic. Influenza A virus was the most frequently detected respiratory virus (8-23% in drainage channels; 3-10% in WWTP influents), while SARS-CoV-2, Influenza B, and RSV were rarely detected. Interpretation: PMMoV-normalized concentrations across most micro-catchments were comparable to WWTP influents, with spatial heterogeneity implying neighborhood-level differences in disease prevalence. Catchment-delineated drainage surveillance has potential to offer spatially resolved public health information in non-sewered settings comparable to sewer-based wastewater monitoring. Funding: Eawag Discretionary Funding

Vaccine hesitancy remains a major public health challenge, highlighting the need for effective strategies to boost vaccine uptake. We conducted a county-randomized trial to evaluate whether a social media campaign grounded in alerts driven by community-level wastewater surveillance could increase COVID-19 and influenza vaccination. Forty New York State counties were selected for an 11-week campaign during fall 2024, with 20 counties assigned to the intervention and 20 serving as controls. The campaign reached more than 16.6 million impressions, with over 77K clicks on the call-to-action link, demonstrating substantial public engagement. During the campaign period, intervention counties administered significantly more COVID-19 vaccine doses ({beta} = 76.7, P = 0.01) but fewer influenza vaccine doses ({beta}= -140.9, P = 0.04) per 100,000 residents per week than control counties. However, season-level analysis showed no significant differences in COVID-19 or influenza vaccination uptake between groups. These findings highlight the potential of alerts from community-level wastewater surveillance to promote vaccination.

Household environments in low-resource settings can become contaminated with fecal matter from multiple sources, including humans and domestic animals. Identifying the source of fecal contamination is critical for designing targeted interventions to reduce exposure to enteric pathogens, particularly for young children who bear the majority of the enteric disease burden. Using data from 140 households with children enrolled in the ECoMiD cohort study in northwestern coastal Ecuador, we (1) characterized source-specific fecal contamination in samples from household floors and maternal and child hands, and (2) identified animal-related and Water, Sanitation and Hygiene (WASH) conditions associated with the presence and concentrations of these markers. We used five qPCR-based microbial source tracking (MST) markers to detect fecal contamination from avian (GFD), canine (DG37), swine (Pig2Bac), ruminant (Rum2Bac), and human (HF183) sources. Prevalence ratios (PR) and mean differences comparing the presence/absence and concentration, respectively, of MST markers between households with and without each animal-related or WASH condition were estimated using generalized linear models with Poisson and Gaussian distributions. Animal MST markers tracked strongly with several animal-related conditions, whereas associations between the human MST marker and household demographic and WASH conditions were more limited. Animal ownership (PR 1.53; 95% CI: 1.04-2.26) was associated with higher prevalence of animal MST markers on floors. Households reporting animal feces indoors had higher prevalence of animal MST markers on floors (PR 1.84; 95% CI: 1.17-2.89), and higher concentrations of animal MST markers on child hands (mean difference 0.27 gene copies (gc)/m2; 95% CI: 0.12-0.41) and maternal hands (mean difference 0.10 gc/m2; CI: 0.02-0.18). Animal feces left unremoved outside the home were associated with higher prevalence of animal MST markers on maternal hands (PR 2.31; 95% CI: 1.11-4.81). Mothers reporting direct contact with animals had higher concentrations of animal MST markers on their children hands (mean difference 0.12 gc/m2; 95% CI: 0.02-0.21). Higher FECEZ scores, an overall metric for animal exposure, were associated with higher prevalence of animal MST markers on maternal hands (PR 2.94; 95% CI: 1.17-7.40). For human fecal contamination, the presence of E. coli on child hands was associated with higher prevalence of human MST markers on floors (PR 1.30; 95% CI: 1.00-1.68). Our findings reinforce household floors and maternal and child hands as key reservoirs of fecal contamination and point to future potential targets worth exploring for interventions in similar high-burden settings.

Freshwater ecosystems in Scotland are increasingly threatened by multiple interacting stressors, including pollution, hydrological alteration, land use change, and climate-driven pressures. Scotland's rivers are amongst the most physically diverse and dynamic in the UK, contributing significantly to the country-s economy and natural heritage. Monitoring 125,000 km of waterways presents an issue, with limited funding and capacity of environmental agencies creating an environmental monitoring deficit at a time when robust data are essential for delivering national and global biodiversity targets. Citizen science offers a scalable, community driven approach to strengthening environmental evidence. This study evaluates the development, implementation, and outcomes of Guardians of our Rivers (GooR), a nationwide citizen science programme using macroinvertebrate-based river health assessments based on the Anglers' Riverfly Monitoring Initiative (RMI) established by the Riverfly Partnership. Between 2022 and 2025, GooR trained more than 850 volunteers, established 123 monitoring sites across Scotland, and generated over 860 surveys-surpassing the previous 16 years of aquatic invertebrate monitoring efforts. Standardised field training, full equipment provision, and structured support enabled high-quality data collection across diverse catchments. The establishment of nationally applied trigger and target thresholds created a consistent mechanism for detecting ecological deterioration and ensured that verified trigger breaches (n = 39 in 2025) resulted in formal investigation or follow-up. Analysis of national abundance patterns revealed ecological and biogeographic trends across the eight RMI taxa, confirming data sensitivity to habitat differences, water quality, and regional pressures. A detailed case study of the Lothian Esk catchment demonstrated the programme's capacity to detect seasonal macroinvertebrate dynamics and site level ecological trajectories over time. Overall, GooR illustrates how well-designed and well-supported citizen science can deliver high resolution spatiotemporal datasets, enhance early warning systems, empower communities, and make a meaningful contribution to promoting river health. Importantly, GooR forged a working partnership with Scottish Environmental Protection Agency (SEPA) that allowed communities to not only gather data but also transformed the way citizen science is recognized as contributing to freshwater conservation. Continued investment and long-term support will be essential to sustain these gains and realise the full potential of citizen-driven freshwater stewardship.

Subsurface tile drainage rapidly transports nutrients and biological contaminants to surface waters, yet multi-year evaluations of drainage water management (DWM) effects on nutrients, Escherichia coli, and antibiotic resistance genes (ARGs) remain limited. A paired-field design with high-frequency soil moisture monitoring was used to quantify water yield, dissolved nitrogen, phosphorus, and Escherichia coli (E. coli) over seven and eight water years, and ARGs (tetM, tetW, ermB, sul1) over two years in southern Michigan. Soil moisture at tile depth (~75 cm) was higher under controlled drainage, confirming that DWM increases field water-holding capacity. Compared to the free drainage field, DWM reduced cumulative tile discharge by 43% and annual nutrient yields by 46-83% for nitrate and 12-82% for soluble reactive phosphorus, but effects on ammonium were variable. Average daily nutrient yields declined by ~50% over the study period, driven primarily by managed periods. Nutrient concentrations did not differ between treatments, indicating that yield reductions resulted from decreased water loss. Mean daily E. coli yields declined by 71% over the study period, and concentrations were 46% lower under controlled drainage. Controlled drainage reduced tetM and sul1 ARG concentrations and yields during managed periods and throughout the study; however, sensitivity analyses showed that these effects were strongly influenced by a high-precipitation event. After excluding the event, differences in ARG concentrations were no longer detected, although ARG yields remained 43% lower during managed periods. These findings highlight the potential for DWM to mitigate nutrient, microbial, and antibiotic resistance transport from agricultural drainage systems.

Biological filtration in newly established aquaria depends on the establishment of nitrifying microorganisms that prevent accumulation of toxic ammonia and nitrite. Many aquarists use commercial nitrifying supplements to accelerate biofilter establishment and reduce ammonia and nitrite accumulation. However, the microbial composition and in situ efficacy of these products remain poorly characterized. We evaluated the ability of enrichment cultures containing comammox Nitrospira (CX) and the ammonia-oxidizing archaeon Ca. Nitrosotenuis aquarius (AQ) to serve as aquarium nitrifying supplements, tested alongside a conventional supplement (CS) containing ammonia-oxidizing bacteria. Inoculation of new aquaria containing zebrafish (Danio rerio) with nitrifying supplements resulted in distinct nitrifier profiles within biofilters of each treatment group corresponding with significant reductions in peak ammonia and nitrite concentrations, which were most evident when applied at the maximum tested supplement dose. Treating aquaria with CX, AQ, or CS maintained ammonia and nitrite at low concentrations, and CX effectively prevented ammonia and nitrite accumulation through all stages of aquarium operation and biofilter establishment. After removing all fish from the aquaria, ammonia "spike-in" experiments demonstrated biofilters treated with CX and AQ conferred long-term protection against nitrite accumulation following acute ammonia loading events. Whereas 16S rRNA gene sequences associated with CS were rarely detected within biofilter profiles, those associated with CX and AQ established early and persisted temporally. Overall, results demonstrate how nitrifiers might be differentially adapted to home aquarium conditions and the potential of AOA and comammox Nitrospira to improve biofilter establishment and maintaining safe water quality in newly established freshwater aquaria.

The contribution of environmental reservoirs to antimicrobial resistance (AMR) acquisition in humans remains poorly quantified, despite extensive evidence that resistant bacteria and resistance genes circulate through wastewater, surface waters, food and other environmental matrices. The central difficulty is no longer to demonstrate that these reservoirs are connected, but to quantify the direction and relative contribution of the pathways linking environmental AMR to human acquisition. Here, we synthesize the main processes that need to be represented at the interface between the environment and humans and propose a mechanistic framework for Escherichia coli producing extended spectrum beta lactamases (ESBL Ec), linking human, water and food compartments. The framework explicitly represents contamination of the environment by humans and multiple routes of human exposure to environmental reservoirs, including drinking water, recreational water exposure and food contamination mediated by irrigation. We apply the model to two contrasting illustrative settings, France and Madagascar, and use scenarios involving antibiotic use, environmental contamination and climate to explore how changes in specific drivers propagate across compartments. The simulations show responses that depend strongly on the compartment, while sensitivity analyses identify wastewater treatment efficiency and parameters describing transmission, exposure and environmental selection at specific interfaces as influential components of the system. The framework is used to explore how different transmission pathways and environmental drivers can shape AMR dynamics across interconnected human and environmental compartments. By comparing contrasting scenarios and identifying the parameters that most strongly influence model behaviour, we highlight both potential leverage points and critical gaps in current empirical knowledge. More broadly, this work illustrates how decomposing One Health AMR into tractable reservoir interfaces can help structure future data collection and progressively improve our ability to quantify transmission between reservoirs.

Wastewater-based epidemiology (WBE) has emerged as a powerful population-level surveillance tool, but its coverage is structurally concentrated in in-network urban areas, potentially leaving rural populations underrepresented. Routine human movement between sewered (in-network) and unsewered (off-network) areas may, however, cause wastewater treatment plant (WWTP) measurements to reflect infectious disease dynamics beyond sewer boundaries. We evaluated this hypothesis using daily clinical COVID-19 testing data (January 2021-April 2022) across New York State excluding New York City (NYC). We disaggregated weekly cases and tests into in-network (WWTP catchment area) and off-network (outside WWTP catchment area) components applied to two geographic frameworks: administrative counties (N = 53 mixed-coverage) and mobility-defined communities identified through Walktrap community detection applied to census tract-level movement networks (N = 32 mixed-coverage). In/off-network COVID-19 trends were strongly correlated under both frameworks. County-level statewide aggregate correlations were high (incidence r = 0.994, positivity r = 0.996), as were individual county correlations (median r = 0.909 and 0.932, respectively). Mobility-defined community-level statewide correlations were similarly strong (r = 0.990 and 0.992), with comparable unit-level medians (r = 0.877 and 0.894). The mobility-defined community framework provided better population balance between in-network and off-network strata (87.5% vs. 69.8% in balanced range) and a higher floor on representativeness (minimum r = 0.440 vs. 0.177). Population size was the dominant predictor of in-network/off-network alignment at both scales; wastewater infrastructure density and off-network signal variability provided additional explanatory power at the mobility-defined community level. WWTPs broadly represent COVID-19 dynamics in surrounding off-network populations, supporting their use as sentinel surveillance sites. Representativeness weakens in smaller, more rural communities, and mobility-defined communities provide a complementary framework for identifying where this occurs.