Salmonella enterica serovar Typhi (S. Typhi), the causative agent of typhoid fever, is notoriously difficult to identify in environmental samples (e.g., water, wastewater, and sewage runoff), due to an overabundance of Salmonella spp. and inadequately selective culture methods. To bypass difficulties with isolate recovery, a two-step molecular method for directly identifying S. Typhi in environmental samples was developed, utilizing an initial real-time polymerase chain reaction (qPCR) screening for presumptive S. Typhi identification followed by sequencing of qPCR products for confirmation. The qPCR assay exhibited a limit of detection of 63.8 gene copies per reaction and a limit of quantification of 638 copies per reaction. When tested against 44 S. enterica serovars, amplification occurred in S. Typhi and 7 non-Typhi serovars (Bareilly, Irumu, Lomalinda, Manchester, Moero, Napoli, and Oslo), while 36 of 43 nontarget serovars did not amplify, corresponding to 83.7% specificity. Amplicons were Sanger sequenced, and Typhi was differentiated from nontyphoidal serovars by a single nucleotide substitution identified in silico. In seeded water concentrates, the assay detected as low as 5 & times; 10(2) CFU/mL, demonstrating utility in complex environmental matrices.

To examine trends in US drinking water outbreaks from 1920 to 2020, we evaluated US drinking water outbreaks documented in the National Outbreak Reporting System and from 4 historic publications dating back to 1920. Before the drinking water regulations of the 1970s, enteric pathogens were the most reported (n = 393; 52%) etiologies. Most outbreaks occurred in individual or private water systems (n = 245; 32%). After major regulations, biofilm-associated outbreaks emerged (n = 343; 32%), and most outbreaks (n = 600; 55%) occurred in community water systems. Biofilm-associated pathogens are an emerging concern in water systems. These findings highlight the importance of drinking water regulations, routine inspections of private wells, and building water management programs. Waterborne disease outbreak investigations and reporting to surveillance systems are essential to identifying factors contributing to outbreaks that can be addressed to improve drinking water policy, practices, and public understanding. As pathogens, drinking water distribution systems, and environmental factors change, identifying etiologic agents and contributing factors in waterborne outbreaks can guide future drinking water policies. (Am J Public Health. 2026;116(9): 1387-1396. https://doi.org/10.2105/AJPH.2026.308475).

BACKGROUND:Low pressure events (LPEs), defined as a water service disruption that presumably lowers system water pressure, can cause drinking water contamination, resulting in increased illness risk to consumers. OBJECTIVES:This study sought to examine whether LPEs increase the risk for highly credible acute gastrointestinal illness (HCGI) and acute respiratory illness (ARI) and to compare water quality in exposed and unexposed areas in the United States. METHODS:A matched cohort study was conducted during the period 2015-2019. For each LPE, household survey exposed areas were matched 1:2 with unexposed areas based on water-main size and material at the point of repair, as well as the housing type and demographic characteristics of the local population from the most recent census tract data. Water samples were collected to monitor physicochemical and microbiological water quality parameters. Households (HHs) were surveyed about water use and illness during the 2 wk after the LPE. Multivariable log-binomial models clustered on utility and LPE number were used to investigate associations between LPE exposure and HCGI and ARI. RESULTS:Five water utilities reported 58 LPEs, including planned maintenance (76%) and emergency (24%) events. Controlling for livestock near home, private well presence, number of people in HH, and travel away from home, exposed HHs were at higher risk of HCGI in comparison with unexposed HHs (risk ratio=1.20; 95% confidence interval: 1.05, 1.37). No associations between LPE and ARI were detected. Certain LPEs characteristics like pipe material, size, and depth were associated with an increased HH HCGI risk. HHs experiencing LPEs where low disinfectant residual, high adenosine triphosphate, or general Bacteroidales were detected in water following an LPE repair were also at a higher risk for HCGI. CONCLUSIONS:LPEs were associated with 20% higher risk of HCGI in HHs. Planned improvements to water distribution system infrastructure, adherence to industry standard distribution repair practices, and water monitoring following pipe repairs could supplement community alert systems to reduce illnesses from LPEs. https://doi.org/10.1289/EHP15564.

We reviewed boil water guidance from 5 public health agencies and noted differences in boil definition, duration, and elevation adjustment. Publishing evidence-based models could clarify the scientific rationale, promote consensus, and minimize likelihood of incomplete water treatment or excess use of limited fuel resources during emergencies and in backcountry settings.

IntroductionFreshwater sources (eg, lakes, ponds, rivers, or streams) can be contaminated by pathogens. Ingesting water from these sources can cause illness if the water is insufficiently treated.MethodThe Waterborne Disease and Outbreak Surveillance System (WBDOSS) collects data on waterborne disease outbreaks associated with drinking water, recreational water, other nonrecreational water, and undetermined exposures to water. We analyzed outbreaks reported to WBDOSS that involved ingesting water from freshwater sources in outdoor settings.ResultFrom 2000 through 2022, public health officials in 16 jurisdictions reported 32 outbreaks associated with ingesting water from insufficiently treated freshwater sources. These outbreaks resulted in 437 illnesses, 4 hospitalizations, and no reported deaths. Giardia was implicated in 69% of outbreaks, and Campylobacter was implicated in 28% of total cases. Water from rivers or streams was implicated in 75% of outbreaks. In half the reported outbreaks, water treatment was not attempted. Individuals were primarily exposed in outdoor recreational areas (eg, public outdoor areas, state parks, campgrounds), with most illnesses occurring in those aged 10-19 years.ConclusionThis is the first summary dedicated to outbreaks associated with ingesting freshwater. These outbreaks can be mitigated using potable water sources, when available, or appropriate water treatment. Public health and provider efforts could include engaging the public-especially those who spend time in the backcountry-regarding health risks and encouraging hygiene, safe disposal of feces, and recommended water treatment methods. Healthcare providers should be encouraged to ask individuals about potential exposure to water from outdoor freshwater sources when presenting with gastrointestinal illness.

The free-living thermophilic amoeba Naegleria fowleri (N. fowleri) causes the highly fatal disease primary amoebic meningoencephalitis. The environmental conditions that are favorable to the growth and proliferation of N. fowleri are not well-defined, especially in northern regions of the United States. In this study, we used culture-based methods and multiple molecular approaches to detect and analyzeN. fowleri and other Naegleria spp. in water, sediment, and biofilm samples from five hot spring sites in Grand Teton National Park, Wyoming, U.S.A. These results provide the first detections of N. fowleri in Grand Teton National Park and provide new insights into the distribution of pathogenic N. fowleri and other nonpathogenic Naegleria spp. in natural thermal water systems in northern latitudes.

Safe and hygienic management of human waste is essential in humanitarian settings. Urine-diverting dry toilets (UDDTs) can enable this management in some humanitarian emergency settings. A seeded, longitudinal environmental study was conducted in Hiloweyn refugee camp, Dollo Ado, Ethiopia, to measure Escherichia coli and Ascaris suum ova inactivation within closed UDDT vaults and to document environmental conditions (temperature, moisture content, and pH) that could influence inactivation. Hiloweyn camp represented an optimal location for a desiccation-based sanitation technology such as the UDDT. E. coli and Ascaris ova inactivation was observed in UDDTs under warm, dry, alkaline conditions at 6, 9, and 12 months of storage; UDDTs with samples containing <1000 E. coli/g total solids increased from 30 % to 95 % over 12 months, and a >2.8-log10 reduction in Ascaris ova viability was observed after 6 months. Additional laboratory-based studies were conducted to provide insights into the field study findings and study the impact of hydrated lime on E. coli and Ascaris ova inactivation. Results suggest that adding hydrated lime to elevate pH > 12 may increase inactivation and decrease storage time. Overall, UDDTs could contribute to the safe and hygienic management of human waste in comparable warm and dry humanitarian settings.

To provide guidance to medical providers, wilderness users, and travelers, the Wilderness Medical Society convened an expert panel to develop evidence-based guidelines for treating water in situations where the potability of available water is not assured, including wilderness and international travel, areas impacted by disaster, and other areas without adequate sanitation. The guidelines present the available methods for reducing or eliminating microbiological contamination of water for individuals, groups, or households; evaluation of their effectiveness; and practical considerations. The evidence base includes both laboratory and clinical publications. The panel graded the recommendations based on the quality of supporting evidence and the balance between benefits and risks/burdens according to the criteria published by the American College of Chest Physicians.

More than 7.15 million cases of domestically acquired infectious waterborne illnesses occurred in the United States in 2014, causing 120,000 hospitalizations and 6,600 deaths. We estimated disease incidence for 17 pathogens according to recreational, drinking, and nonrecreational nondrinking (NRND) water exposure routes by using previously published estimates. In 2014, a total of 5.61 million (95% credible interval [CrI] 2.97-9.00 million) illnesses were linked to recreational water, 1.13 million (95% CrI 255,000-3.54 million) to drinking water, and 407,000 (95% CrI 72,800-1.29 million) to NRND water. Recreational water exposure was responsible for 36%, drinking water for 40%, and NRND water for 24% of hospitalizations from waterborne illnesses. Most direct costs were associated with pathogens found in biofilms. Estimating disease burden by water exposure route helps direct prevention activities. For each exposure route, water management programs are needed to control biofilm-associated pathogen growth; public health programs are needed to prevent biofilm-associated diseases.

Outbreaks associated with treated recreational water can be caused by pathogens or chemicals in aquatic venues such as pools, hot tubs, water playgrounds, or other artificially constructed structures that are intended for recreational or therapeutic purposes. For the pseriod 2015-2019, public health officials from 36 states and the District of Columbia (DC) voluntarily reported 208 outbreaks associated with treated recreational water. Almost all (199; 96%) of the outbreaks were associated with public (nonbackyard) pools, hot tubs, or water playgrounds. These outbreaks resulted in at least 3,646 cases of illness, 286 hospitalizations, and 13 deaths. Among the 155 (75%) outbreaks with a confirmed infectious etiology, 76 (49%) were caused by Cryptosporidium (which causes cryptosporidiosis, a gastrointestinal illness) and 65 (42%) by Legionella (which causes Legionnaires' disease, a severe pneumonia, and Pontiac fever, a milder illness with flu-like symptoms). Cryptosporidium accounted for 2,492 (84%) of 2,953 cases resulting from the 155 outbreaks with a confirmed etiology. All 13 deaths occurred in persons affected by a Legionnaires' disease outbreak. Among the 208 outbreaks, 71 (34%) were associated with a hotel (i.e., hotel, motel, lodge, or inn) or a resort, and 107 (51%) started during June-August. Implementing recommendations in CDC's Model Aquatic Health Code (MAHC) (1) can help prevent outbreaks associated with treated recreational water in public aquatic venues.

The recent increase of reported cyclosporiasis outbreaks associated with fresh produce has highlighted the need for understanding environmental transmission of Cyclospora cayetanensis in agricultural settings and facilities. Conducting such environmental investigations necessitates robust sample collection and analytical methods to detect C. cayetanensis in water samples. This study evaluated three sample collection methods for recovery of C. cayetanensis oocysts from water samples during seeded recovery experiments. Two filtration-based methods, dead-end ultrafiltration (DEUF) and USEPA Method 1623.1, were evaluated for oocyst recovery from irrigation water. A non-filter-based method, continuous flow centrifugation (CFC), was evaluated separately for recovery from creek water and spent produce wash water. Median C. cayetanensis recovery efficiencies were 17% for DEUF and 16–22% for Method 1623.1. The DEUF method proved to be more robust than Method 1623.1, as the recovery efficiencies were less variable and the DEUF ultrafilters were capable of filtering larger volumes of high-turbidity water without clogging. Median C. cayetanensis recovery efficiencies for CFC were 28% for wash water and 63% for creek water, making it a viable option for processing water with high turbidity or organic matter. The data from this study demonstrate the capability of DEUF and CFC as filter-based and non-filter-based options, respectively, for the recovery of C. cayetanensis oocysts from environmental and agricultural waters.

The Centers for Disease Control and Prevention (CDC) will be releasing the 4th edition of the Model Aquatic Health Code (MAHC, www cdc gov/mahc) in the coming months The MAHC represents a collaboration among local, state, and federal public health officials, particularly environmental health practitioners, and representatives of the aquatics sector to optimize prevention of illness and injury associated with public aquatic venues (e g , pools, hot tubs, and water playgrounds) Cyanuric acid (CYA) binds to chlorine to prevent it from being degraded by UV light from the sun Consequently, CYA increases the amount of time it takes for chlorine to inactivate pathogens CYA is sold as a stand-alone product or as chlorinated isocyanurates (chlorine and CYA, commonly known as dichlor or trichlor) In 2015, CMAHC established a CYA ad hoc committee that included representatives from across the CYA industry and researchers but did not include state or local public health officials CMAHC charged the committee to develop guidance on CYA concentrations

Hand drying is the critical, final step of handwashing. A cross-sectional survey of U.S. adults assessed self-reported hand drying practices in public bathrooms and found increased preference for using electric hand dryers, wiping hands on clothing, and shaking hands and decreased preference for using paper towels during the COVID-19 pandemic relative to before. Respondents expressed concerns about contacting SARS-CoV-2 when touching surfaces in public bathrooms which may be influencing self-reported drying method preference.

We report a specific region of Giardia spp. 18S ribosomal RNA (18S rDNA) that serves as an ideal target for quantitative PCR (qPCR) detection and sequencing to identify Giardia species, including the clinically-relevant G. duodenalis, in clinical and environmental samples. The presence of multiple copies of the 18S rDNA gene and variations in the selected 18S genomic region enabled the development of a rapid, sensitive qPCR screening method for the detection of Giardia spp. The analytical sensitivity of the Giardia qPCR assay was determined to be a cyst equivalent of 0.4 G. duodenalis cysts per PCR reaction. Amplicon sequencing of the PCR product confirmed Giardia spp. detection and among the 35 sequences obtained, 31, 3 and 1 isolates were classified as belonging to G. duodenalis, G. microti and G. muris, respectively. The TaqMan assay reported here may be useful for the detection of low levels of Giardia in clinical and environmental samples, and further enables the effective use of direct sequencing of the PCR product for Giardia confirmation and to identify major species of Giardia, including G. duodenalis.

In June 2017, the Pennsylvania Department of Health (PADOH) was notified of multiple norovirus outbreaks associated with 179 ill individuals who attended separate events held at an outdoor venue and campground over a month period. Epidemiologic investigations were unable to identify a single exposure route and therefore unable to determine whether there was a persistent contamination source to target for exposure mitigation. Norovirus was detected in a fresh recreational water designated swimming area and a drinking water well. A hydrogeological site evaluation suggested a nearby septic leach field as a potential contamination source via ground water infiltration. Geological characterization revealed a steep dip of the bedrock beneath the septic leach field toward the well, providing a viral transport pathway in a geologic medium not previously documented as high risk for viral ground water contamination. The human-associated microbial source tracking (MST) genetic marker, HF183, was used as a microbial tracer to demonstrate the hydrogeological connection between the malfunctioning septic system, drinking water well, and recreational water area. Based on environmental investigation findings, venue management and local public health officials implemented a series of outbreak prevention strategies including discontinuing the use of the contaminated well, issuing a permit for a new drinking water well, increasing portable toilet and handwashing station availability, and promoting proper hand hygiene. Despite the outbreaks at the venue and evidence of ground water contamination impacting nearby recreational water and the drinking water well, no new norovirus cases were reported during a large event one week after implementing prevention practices. This investigation highlights a new application for human-associated MST methods to trace hydrological connections between multiple fecal pollutant exposure routes in an outbreak scenario. In turn, pollutant source information can be used to develop effective intervention practices to mitigate exposure and prevent future outbreaks associated with human fecal contaminated waters.

Wastewater surveillance, the measurement of pathogen levels in wastewater, is used to evaluate community-level infection trends, augment traditional surveillance that leverages clinical tests and services (e.g., case reporting), and monitor public health interventions (1). Approximately 40% of persons infected with SARS-CoV-2, the virus that causes COVID-19, shed virus RNA in their stool (2); therefore, community-level trends in SARS-CoV-2 infections, both symptomatic and asymptomatic (2) can be tracked through wastewater testing (3-6). CDC launched the National Wastewater Surveillance System (NWSS) in September 2020 to coordinate wastewater surveillance programs implemented by state, tribal, local, and territorial health departments to support the COVID-19 pandemic response. In the United States, wastewater surveillance was not previously implemented at the national level. As of August 2021, NWSS includes 37 states, four cities, and two territories. This report summarizes NWSS activities and describes innovative applications of wastewater surveillance data by two states, which have included generating alerts to local jurisdictions, allocating mobile testing resources, evaluating irregularities in traditional surveillance, refining health messaging, and forecasting clinical resource needs. NWSS complements traditional surveillance and enables health departments to intervene earlier with focused support in communities experiencing increasing concentrations of SARS-CoV-2 in wastewater. The ability to conduct wastewater surveillance is not affected by access to health care or the clinical testing capacity in the community. Robust, sustainable implementation of wastewater surveillance requires public health capacity for wastewater testing, analysis, and interpretation. Partnerships between wastewater utilities and public health departments are needed to leverage wastewater surveillance data for the COVID-19 response for rapid assessment of emerging threats and preparedness for future pandemics.

The procedure described here provides instructions for detection of Cryptosporidium recovered from large-volume water samples. Water samples are collected by dead-end ultrafiltration in the field and ultrafilters are processed in a laboratory. Microbes recovered from the filters are further concentrated and subjected to Cryptosporidium isolation or nucleic acid extraction methods for the detection of Cryptosporidium oocysts or Cryptosporidium DNA.

Hog production takes place mostly in large concentrated animal feeding operations (CAFOs) where waste is managed by storing in lagoons prior to land application of lagoon liquid. Salmonella, including antibiotic-resistant Salmonella, have been found in the farm environment and lagoons. The objective of this research was to determine whether Salmonella resistant to clinically relevant antibiotics were present in wastewaters and surface waters from hog CAFOs. Samples of hog waste and on farm environmental waters were analysed for Salmonella, which were tested for antimicrobial susceptibility. The highest percentage of resistant isolates were found in raw waste flushed from hog houses and in lagoon wastewater; few resistant isolates were found in on-farm surface water. Resistance to sulphamethoxazole was most common, mostly in waste samples and less commonly in surface water, followed by chloramphenicol and ampicillin. No resistance to cephalosporin or fluoroquinolones was found. Resistance to clinically relevant antibiotics was commonly found in Salmonella from hog waste but was less extensive in farm surface waters. Management of wastes from hog CAFOs should be designed to further reduce the risk of human exposures resulting from environmental contamination with Salmonella. Significance and Impact of the Study This study suggests antibiotic-resistant Salmonella were common in hog wastes and present in environmental waters associated with hog CAFOs. Low levels of antibiotic-resistant Salmonella in on-farm stream waters suggest surface waters could have been contaminated, potentially serving as a mechanism of off-farm transport. Since the study, there have been multiple economic, regulatory and practice changes at the federal, state and industry level. These include regulation of antibiotic use and animal waste treatment, vertical integration in the industry and changes in antibiotic use practice. This study is a useful historical baseline against which current antibiotic resistance trends can be measured.

Washing hands often, especially during times when one is likely to acquire and spread pathogens,* is one important measure to help prevent the spread of SARS-CoV-2, the virus that causes coronavirus disease 2019 (COVID-19), as well as other pathogens spread by respiratory or fecal-oral transmission (1,2). Studies have reported moderate to high levels of self-reported handwashing among adults worldwide during the COVID-19 pandemic (3-5)†; however, little is known about how handwashing behavior among U.S. adults has changed since the start of the pandemic. For this study, survey data from October 2019 (prepandemic) and June 2020 (during pandemic) were compared to assess changes in adults' remembering to wash their hands in six situations.§ Statistically significant increases in reported handwashing were seen in June 2020 compared with October 2019 in four of the six situations; the odds of remembering to wash hands was 2.3 times higher among respondents after coughing, sneezing, or blowing their nose, 2.0 times higher before eating at a restaurant, and 1.7 times higher before eating at home. Men, young adults aged 18-24 years, and non-Hispanic White (White) adults were less likely to remember to wash hands in multiple situations. Strategies to help persons remember to wash their hands frequently and at important times should be identified and implemented, especially among groups reporting low prevalence of remembering to wash their hands.