Occurrence and concentrations of traditional and emerging contaminants in onsite wastewater systems and water supply wells in eastern North Carolina, USA.

Onsite wastewater treatment systems (OWTSs) and private wells are commonly used in Eastern North Carolina, USA. Water from private wells is not required to be tested after the initial startup, and thus persons using these wells may experience negative health outcomes if their water is contaminated with waste-related pollutants including bacteria, nitrate or synthetic chemicals such as hexafluoropropylne oxide dimer acid and its ammonium salt (GenX). Water samples from 18 sites with OWTSs and groundwater wells were collected for nitrate, Escherichia coli (E. coli), total coliform, and GenX concentration analyses. Results showed that none of the 18 water supplies were positive for E. coli, nitrate concentrations were all below the maximum contaminant level of 10 mg L-1, and one well had 1 MPN 100 mL-1 of total coliform. However, GenX was detected in wastewater collected from all 18 septic tanks and 22% of the water supplies tested had concentrations that exceeded the health advisory levels for GenX. Water supplies with low concentrations of traditionally tested for pollutants (nitrate, E. coli) may still pose health risks due to elevated concentrations of emerging contaminants like GenX and thus more comprehensive and routine water testing is suggested for this and similar persistent compounds.

Coastal Tourism and Its Influence on Wastewater Nitrogen Loading: A Barrier Island Case Study.

Package treatment plants (PTPs) are facilities designed to treat onsite wastewater for small communities, commercial, and residential developments. PTPs are being utilized in a growing number of coastal communities. This study estimated the effects of coastal tourism on onsite wastewater nitrogen (N) inputs to a barrier island surficial aquifer (Bogue Banks, NC). The N-removal effectiveness was assessed for seven PTPs that treated wastewater from vacation properties using a range of technologies: extended aeration; sequencing batch reactor; and advanced media filtration. Influent and effluent wastewater samples were collected monthly from Feb. 2014 to Jan. 2015 and analyzed for particulate and dissolved N. Increased summer visitation associated with coastal tourism resulted in an increase in water use, wastewater inputs, and PTP N loading to the surficial aquifer. However, extended aeration systems did not have significantly elevated TN loads during the summer months because their treatment efficiency increased. N inputs associated with coastal tourism made up approximately 51% of the annual wastewater-related N load to the surficial aquifer. Onsite wastewater N-loading to the surficial aquifer (6.7 kg-N/ha/yr) appeared to be the dominant source of N loading on the island. Water quality data indicated that these N inputs have resulted in increased groundwater NO3 concentrations in the surficial aquifer. Overall, wastewater inputs added approximately 4.6 cm of groundwater recharge annually to the island. Coastal tourism can result in measurable increases in wastewater N loading, groundwater nitrogen concentrations, and groundwater recharge.

Phosphate treatment by onsite wastewater systems in nutrient-sensitive watersheds of North Carolina's Piedmont.

The goal of this study was to gain a better understanding of the PO4-P treatment efficiency of onsite wastewater systems (OWS) installed in nutrient-sensitive watersheds of the North Carolina Piedmont. Four OWS including two conventional and two single-pass sand filter (SF) systems were evaluated at sites with clay-rich soils. Piezometers were installed near all of the OWS, and down-gradient from the conventional OWS for groundwater collection and characterization. Septic tanks, groundwater, SF effluent, and surface waters were sampled each season during 2015 (five times) and analyzed for PO4-P and Cl concentrations and for various environmental parameters. The conventional and SF OWS reduced PO4-P concentrations by an average of 99% and 90%, respectively, before discharge to surface waters. Mass-load reductions of PO4-P were also greater for the conventional OWS (mean 95%), relative to SF (83%) systems. The effluents discharged by SF OWS were influencing surface water quality. Additional treatment of the effluent from single-pass SF with reactive media is suggested, along with monitoring of the final effluent for PO4-P concentrations. This research provides important information that is absent from the published literature concerning PO4-P contributions to water resources from OWS in clay soils.

Seat Belt Usage Interventions for Motor Vehicle Crash Prevention on the Pine Ridge Indian Reservation, South Dakota.

Motor vehicle crashes (MVC) are the leading cause of death from severe injuries on the Pine Ridge Indian Reservation (PRIR), averaging 16 MVC deaths per year from 2002 to 2011. The Sacred Cargo Coalition was established in PRIR in 2007 to implement intervention strategies to increase seat belt usage and reduce MVC fatalities, including seat belt law enforcement, creating a traffic court system, and educational campaigns on MVC prevention. The study described in this article examined the effectiveness of the interventions on increasing the seat belt usage rates and reducing MVC deaths. Secondary data were collected from the National Highway Traffic Safety Administration and other federal and local agencies. Seat belt usage rates increased an average of 6.8 percentage points from 2007 (10%) to 2012 (44%). MVC fatalities decreased by 46.7% from the preintervention to the intervention period. Maintenance and improvement of the intervention strategies may be achieved by seeking additional funding and including appropriate engineering activities in PRIR.

Groundwater and stream E. coli concentrations in coastal plain watersheds served by onsite wastewater and a municipal sewer treatment system.

The goal of this study was to determine if onsite wastewater treatment systems (OWS) were influencing groundwater and surface water Escherichia coli concentrations in a coastal plain watershed. Piezometers for groundwater monitoring were installed at four residences served by OWS and five residences served by a municipal wastewater treatment system (MWS). The residences were located in two different, but nearby (<3 km), watersheds. Effluent from the four septic tanks, groundwater from piezometers, and the streams draining the OWS and MWS watersheds were sampled on five dates between September 2011 and May 2012. Groundwater E. coli concentrations and specific conductivity were elevated within the flow path of the OWS and near the stream, relative to other groundwater sampling locations in the two watersheds. Groundwater discharge in the OWS watershed could be a contributor of E. coli to the stream because E. coli concentrations in groundwater at the stream bank and in the stream were similar. Stream E. coli concentrations were higher for the OWS in relation to MWS watersheds on each sampling date. Water quality could be improved by ensuring OWS are installed and operated to maintain adequate separation distances to water resources.

Fate and transport of enteric microbes from septic systems in a coastal watershed.

Onsite wastewater treatment systems (OWTS) are commonly used in coastal areas to treat household wastewater. These systems represent potential sources of fecal pollution of groundwater and nearby surface water. OWTS are expected to reduce microbial concentrations in wastewater; however, system and environmental factors can affect treatment efficiency and impacts on ground and surface water. In the study of OWTS described in this article, the authors sampled septic tanks and groundwater at two households in coastal North Carolina between October 2009 and October 2011. Samples were tested for the fecal indicator microbes E. coli, enterococci, and Clostridium perfringens. Microbial source tracking was also performed in year two. Results showed that enteric microbe concentrations in groundwater significantly decreased with distance from the OWTS. Human markers of fecal contamination were also detected in the OWTS and downgradient groundwater, indicating that OWTS can impact the microbial quality of shallow groundwater.

Nitrogen and carbon dynamics beneath on-site wastewater treatment systems in Pitt County, North Carolina.

On-site wastewater treatment systems (OWS) are a potentially significant non-point source of nutrients to groundwater and surface waters, and are extensively used in coastal North Carolina. The goal of this study was to determine the treatment efficiency of four OWS in reducing total dissolved nitrogen (TDN) and dissolved organic carbon (DOC) concentrations before discharge to groundwater and/or adjacent surface water. Piezometers were installed for groundwater sample collection and nutrient analysis at four separate residences that use OWS. Septic tank effluent, groundwater, and surface water samples (from an adjacent stream) were collected four times during 2012 for TDN and DOC analysis and pH, temperature, electrical conductivity, and dissolved oxygen measurements. Treatment efficiencies from the tank to the groundwater beneath the drainfields ranged from 33 to 95% for TDN and 45 to 82% for DOC, although dilution accounted for most of the concentration reductions. There was a significant positive correlation between nitrate concentration and separation distance from trench bottom to water table and a significant negative correlation between DOC concentration and separation distance. The TDN and DOC transport (>15 m) from two OWS with groundwater saturated drainfield trenches was significant.

Fate and transport of phosphate from an onsite wastewater system in Beaufort County, North Carolina.

The objectives for the study described in this article were to evaluate the fate and transport of onsite wastewater system (OWS)-derived phosphate from a residential system in Beaufort County, North Carolina, and to determine if current OWS setback regulations are sufficient to prevent elevated phosphate discharge to surface waters. Piezometers were installed in nests at different depths adjacent to drain-field trenches and up- and down-gradient of a residential OWS. Groundwater and septic effluent phosphate concentrations, temperature, pH, dissolved oxygen, and electrical conductivity were monitored every two months from February 2011 to October 2011 (five times). The mean groundwater phosphate concentration beneath the OWS (3.05 +/- 0.74 mg/L) was not significantly different than septic effluent (2.97 +/- 0.76 mg/L) and was elevated relative to background groundwater (0.14 +/- 0.12 mg/L). Groundwater phosphate concentrations were inversely related (r2 = .83) to distance from the system. Onsite system setback regulations may have to be increased (>30 m) in some areas to ensure groundwater phosphate concentrations are reduced to background concentrations before discharge to surface waters.

Evaluation of five years of nursing home inspection forms: structural and hygiene-related violation trends.

Health inspections are performed at nursing homes to identify and reduce risk and to help maintain a safe environment for nursing home residents. The study described in this article aimed to identify the most frequent violations, types of violations (hygiene or structural), and repeat violations in nursing home facilities during health inspections; and to determine if the age of the facility influenced inspection scores. Nursing home health inspection forms (N = 131) completed between 2005 and 2011 in Pitt County, North Carolina, were analyzed. Results indicated that 60% of all violations were hygiene-related and could possibly be corrected without significant financial investments by management. Significant correlations occurred between the total number of violations and the facility age (p = .003) and between the number of repeat violations and total violations (p < .001). The average inspection score for nursing homes could be increased by more than three points if sanitation practices were improved.

Wastewater based epidemiology as a surveillance tool during the current COVID-19 pandemic on a college campus (East Carolina University) and its accuracy in predicting SARS-CoV-2 outbreaks in dormitories.

The COVID-19 outbreak led governmental officials to close many businesses and schools, including colleges and universities. Thus, the ability to resume normal campus operation required adoption of safety measures to monitor and respond to COVID-19. The objective of this study was to determine the efficacy of wastewater-based epidemiology as a surveillance method in monitoring COVID-19 on a college campus. The use of wastewater monitoring as part of a surveillance program to control COVID-19 outbreaks at East Carolina University was evaluated. During the Spring and Fall 2021 semesters, wastewater samples (N = 830) were collected every Monday, Wednesday, and Friday from the sewer pipes exiting the dormitories on campus. Samples were analyzed for SARS-CoV-2 and viral quantification was determined using qRT-PCR. During the Spring 2021 semester, there was a significant difference in SARS-CoV-2 virus copies in wastewater when comparing dorms with the highest number student cases of COVID-19 and those with the lowest number of student cases, (p = 0.002). Additionally, during the Fall 2021 semester it was observed that when weekly virus concentrations exceeded 20 copies per ml, there were new confirmed COVID-19 cases 85% of the time during the following week. Increases in wastewater viral concentration spurred COVID-19 swab testing for students residing in dormitories, aiding university officials in effectively applying COVID testing policies. This study showed wastewater-based epidemiology can be a cost-effective surveillance tool to guide other surveilling methods (e.g., contact tracing, nasal/salvia testing, etc.) to identify and isolate afflicted individuals to reduce the spread of pathogens and potential outbreaks within a community.

2009 pandemic influenza A (H1N1): pathology and pathogenesis of 100 fatal cases in the United States.

In the spring of 2009, a novel influenza A (H1N1) virus emerged in North America and spread worldwide to cause the first influenza pandemic since 1968. During the first 4 months, over 500 deaths in the United States had been associated with confirmed 2009 pandemic influenza A (H1N1) [2009 H1N1] virus infection. Pathological evaluation of respiratory specimens from initial influenza-associated deaths suggested marked differences in viral tropism and tissue damage compared with seasonal influenza and prompted further investigation. Available autopsy tissue samples were obtained from 100 US deaths with laboratory-confirmed 2009 H1N1 virus infection. Demographic and clinical data of these case-patients were collected, and the tissues were evaluated by multiple laboratory methods, including histopathological evaluation, special stains, molecular and immunohistochemical assays, viral culture, and electron microscopy. The most prominent histopathological feature observed was diffuse alveolar damage in the lung in all case-patients examined. Alveolar lining cells, including type I and type II pneumocytes, were the primary infected cells. Bacterial co-infections were identified in >25% of the case-patients. Viral pneumonia and immunolocalization of viral antigen in association with diffuse alveolar damage are prominent features of infection with 2009 pandemic influenza A (H1N1) virus. Underlying medical conditions and bacterial co-infections contributed to the fatal outcome of this infection. More studies are needed to understand the multifactorial pathogenesis of this infection.

High-frequency assessment of air and water quality at a concentration animal feeding operation during wastewater application to spray fields.

Air and water quality at a concentrated animal feeding operation (CAFO) in Eastern North Carolina that uses a covered lagoon and anaerobic digester was evaluated for 2 weeks in August 2020. Real-time PM2.5 mass concentrations were determined using a reference ADR-1500 nephelometer and high-frequency measurements of dissolved inorganic nitrogen (DIN) were evaluated using autonomously logging sensors. Air and water quality parameters were assessed before, during and after wastewater from the lagoon was irrigated onto adjacent spray fields. Reference measurements were conducted alongside a HOBO weather station to collect real-time wind speed and direction, temperature, and humidity measurements. PM2.5 concentrations varied between 0 and 159 µg/m3 with an average concentration of 11 µg/m3, below EPA standard for secondary aerosols of 15 µg/m3. Higher PM2.5 concentrations were observed when wind originated from swine barns but not from covered lagoons. Water quality data showed that DIN concentrations downgradient from the CAFO were elevated relative to upstream concentrations. A groundwater seep that drains a spray field contained the highest average DIN concentration (31.0 ± 12.8 mg L-1), which was 25 times greater than upstream DIN concentrations (1.2 ± 0.8 mg L-1). Average DIN concentration at the downstream station was lower than the seep concentration (8.6 ± 16.2 mg L-1), but approximately 8 times greater than upstream. Air quality data show that the lagoon cover was effective at mitigating air quality degradation, whereas DIN concentrations in water were similar to previous studies on CAFOs using open lagoons. In addition, air and water quality parameters were significantly (p < 0.001) higher after irrigation, indicating possible influence due to ammonia and nitrate elevation. Additional research is needed to compare high-frequency data collected from swine CAFOs using capped and uncapped lagoon systems to better understand spatiotemporal air and water quality trends of this practice.

Detection and characterization of group C rotavirus in Buenos Aires, Argentina, 1997-2003.

The role of group C rotaviruses as a cause of diarrhea was examined among children <17 years of age admitted to a Hospital in a suburban area of Buenos Aires, Argentina between 1997 and 2003. A total of 1,579 fecal samples were screened for group A (RVA) and C (RVC) rotaviruses by two in-house ELISA methods at Quilmes University (UNQ-ELISA). Samples positive, doubtful and negative by RVC specific UNQ-ELISA (n = 246) were examined further for RVC by another in-house ELISA (CDC-ELISA), electron microscopy, RT-PCR, nested PCR, and Southern hybridization. Sensitivity, specificity, and predictive values for each test were determined. While the sensitivity was comparable for the nested PCR and CDC-ELISA methods (82.5%), the molecular methods were slightly more specific. Poorly preserved particles were often seen in fecal samples, suggesting that degradation of RNA could be a factor influencing the performance of molecular methods. The incidence of RVC was estimated to be 3% without apparent differences among seasons. RVC infected patients had a significantly (P < 0.001) higher median age (6 years vs. 1 year) than those with RVA infection. Sequence of the RVC VP7 gene from six Argentinean strains and sequences reported previously in different countries showed high nucleotide (94.4-99.9%) sequence identities, indicating a high degree of conservation for human RVC VP7 genes among strains collected on five continents over a period of 17 years. These findings indicate that RVC is a significant cause of diarrhea and it is necessary to develop simple and sensitive serological methods for its detection.

Nurse staffing and patient outcomes: evolution of an international study.

Industry-wide health sector reforms in the United States, Canada, and Europe have provided a unique opportunity to examine the effects of hospital restructuring on inpatient nursing care and patient outcomes across an array of settings. Seven interdisciplinary research teams--1 each in Alberta, British Columbia, England, Germany, Ontario, Scotland, and the United States--have formed an international consortium whose aim is to study the effects of such restructuring. Each site has enrolled large numbers of hospitals and nurses to explicate the role that organization of nursing care, a target of hospital restructuring, plays in differential patient outcomes. The study seeks to understand more fully the influence of both nurse staffing and the nursing practice environment on patient outcomes. Discussion of the theoretical foundation, study design, and process of developing the study instruments and measures illustrates the process to date, as well as the feasibility of and opportunities inherent in such an international endeavour.

Prevalence of group C rotavirus among children in Rhode Island, United States.

BACKGROUND: Group C rotavirus causes sporadic cases and outbreaks of acute diarrhea in humans but its burden as a cause of severe gastroenteritis in children remains unclear. OBJECTIVES: To investigate the epidemiology and burden of group C rotavirus gastroenteritis among children in Rhode Island, United States. STUDY DESIGN: Diarrhea stool specimens from 124 children < or =10 years of age were collected, screened for group C and A rotavirus by EIA specific for each group, and further examined by nested PCR and Southern hybridization using primers and probes specific to the VP7 gene of human group C rotavirus. Group C rotavirus-positive fecal specimens were also examined by EM. RESULTS: Rotavirus was detected in 73 (59.0%) of 124 fecal samples. These included 53 (42.7%) positive for group A, 5 (4.0%) for group C and 15 (12.1%) for both group A and C rotaviruses. Examination of group C-positive samples by EM revealed the presence of largely empty or damaged rotavirus-like particles. CONCLUSION: These findings indicate that group C rotavirus is an important cause or a contributing cause of diarrhea among infants and older children in Rhode Island, United States.

Development of plaque assays for adenoviruses 40 and 41.

Enteric adenoviruses, important agents of infantile gastroenteritis, are difficult to culture with low titers and limited CPE. Consequently, few plaque assays have been reported and none are used routinely by investigators who may need reproducible quantitative assays for these viruses. CPE in A549 cells (an epithelial lung carcinoma cell line) was induced by isolates of human adenovirus (HAdV) serotypes 40 or 41 that were obtained by prior limited passage in primary cynmolgous monkey kidney (pCMK), human embryonic kidney (HEK), and Graham 293 cells. CPE with HAdV 40 (Dugan strain) and HAdV 41 (Tak strain) inoculated in A549 cells was also observed. Monolayers of A549 cells were inoculated with a low multiplicity of infection (MOI) of the archived stock isolates and harvested at days 10-14 with full CPE. Subsequent passages were harvested in as few as 7 days with 100% CPE to prepare virus stocks for plaque assay. Large individual plaques under agarose overlay were picked prior to staining and clonal stocks prepared. Titers of final stock preparations after six to eight passages in A549 cells were in the range of 5 x 10(7)-1 x 10(8)PFU/ml, which provides adequate virus for quantitative recovery studies. The particle to infectivity (P:I) ratios of the early passages of virus stocks were in the range reported previously. The ratio of non-infectious to infectious particles decreased with successive passages of HAdVs 40 and 41 in A549 cells. The specificity of the assay was confirmed by neutralization of plaques with type-specific antisera. Furthermore, sequence analysis of the HAdVs 40 and 41 plaque forming stocks ruled out contamination with any other HAdVs. The plaque assay developed will be useful for evaluation of virus recovery methods from water, food or other environmental matrices, as well as determination of the efficacy of water treatment techniques for inactivation of these viruses.

Descriptive epidemiology of fatal respiratory outbreaks and detection of a human-related metapneumovirus in wild chimpanzees (Pan troglodytes) at Mahale Mountains National Park, Western Tanzania.

Over the past several years, acute and fatal respiratory illnesses have occurred in the habituated group of wild chimpanzees at the Mahale Mountains National Park, Tanzania. Common respiratory viruses, such as measles and influenza, have been considered possible causative agents; however, neither of these viruses had been detected. During the fatal respiratory illnesses in 2003, 2005 and 2006, regular observations on affected individuals were recorded. Cause-specific morbidity rates were 98.3, 52.4 and 33.8%, respectively. Mortality rates were 6.9, 3.2 and 4.6%; all deaths were observed in infants 2 months-2 years 9 months of age. Nine other chimpanzees have not been seen since the 2006 outbreak and are presumed dead; hence, morbidity and mortality rates for 2006 may be as high as 47.7 and 18.5%, respectively. During the 2005 and 2006 outbreaks, 12 fecal samples were collected from affected and nonaffected chimpanzees and analyzed for causative agents. Analysis of fecal samples from 2005 suggests the presence of paramyxovirus, and in 2006 a human-related metapneumovirus was detected and identified in an affected chimpanzee whose infant died during the outbreak. Our findings provide preliminary evidence that the causative agent associated with these illnesses is viral and contagious, possibly of human origin; and that, possibly more than one agent may be circulating in the population. We recommend that baseline health data be acquired and food wadge and fecal samples be obtained and bio-banked as early as possible when attempting to habituate new groups of chimpanzees or other great apes. For already habituated populations, disease prevention strategies, ongoing health monitoring programs and reports of diagnostic findings should be an integral part of managing these populations. In addition, descriptive epidemiology should be a major component of disease outbreak investigations.

A novel coronavirus associated with severe acute respiratory syndrome.

BACKGROUND: A worldwide outbreak of severe acute respiratory syndrome (SARS) has been associated with exposures originating from a single ill health care worker from Guangdong Province, China. We conducted studies to identify the etiologic agent of this outbreak. METHODS: We received clinical specimens from patients in seven countries and tested them, using virus-isolation techniques, electron-microscopical and histologic studies, and molecular and serologic assays, in an attempt to identify a wide range of potential pathogens. RESULTS: None of the previously described respiratory pathogens were consistently identified. However, a novel coronavirus was isolated from patients who met the case definition of SARS. Cytopathological features were noted in Vero E6 cells inoculated with a throat-swab specimen. Electron-microscopical examination revealed ultrastructural features characteristic of coronaviruses. Immunohistochemical and immunofluorescence staining revealed reactivity with group I coronavirus polyclonal antibodies. Consensus coronavirus primers designed to amplify a fragment of the polymerase gene by reverse transcription-polymerase chain reaction (RT-PCR) were used to obtain a sequence that clearly identified the isolate as a unique coronavirus only distantly related to previously sequenced coronaviruses. With specific diagnostic RT-PCR primers we identified several identical nucleotide sequences in 12 patients from several locations, a finding consistent with a point-source outbreak. Indirect fluorescence antibody tests and enzyme-linked immunosorbent assays made with the new isolate have been used to demonstrate a virus-specific serologic response. This virus may never before have circulated in the U.S. population. CONCLUSIONS: A novel coronavirus is associated with this outbreak, and the evidence indicates that this virus has an etiologic role in SARS. Because of the death of Dr. Carlo Urbani, we propose that our first isolate be named the Urbani strain of SARS-associated coronavirus.

A large outbreak of Brainerd diarrhea associated with a restaurant in the Red River Valley, Texas.

BACKGROUND: In June 1996, an outbreak of chronic diarrhea was reported to the Texas Department of Health (Austin). METHODS: We initiated active case finding, performed 2 case-control studies, and conducted an extensive laboratory and environmental investigation. RESULTS: We identified 114 persons with diarrhea that lasted > or = 4 weeks. Symptoms among 102 patients who were studied included urgency (87%), fatigue (86%), fecal incontinence (74%), and weight loss (73%); the median maximum 24-h stool frequency was 15 stools. Diarrhea persisted for > 6 months in 87% and for > 1 year in 70% of patients who were observed. Fifty-one (89%) of 57 ill persons had eaten at a particular restaurant within 4 weeks before onset, compared with 8 (14%) of 59 matched control subjects (matched odds ratio [OR], undefined; 95% confidence interval [CI], 11.2-infinity). At the restaurant, patients were more likely than their unaffected dining companions to have drunk tap water (OR, 2.8; 95% CI, 1.0-9.9) and to have eaten several specific food items, and they were less likely to have drunk iced tea made from boiled water and store-bought ice (OR, 0.3; 95% CI, 0.05-1.0). A multivariable model that included consumption of tap water and salad bar tomatoes best fit the data. The restaurant had multiple sanitary and plumbing deficiencies. Extensive laboratory and environmental testing for bacterial, parasitic, mycotic, and viral agents did not identify an etiologic agent. CONCLUSIONS: The clinical, laboratory, and epidemiologic findings are consistent with those of previous outbreaks of Brainerd diarrhea. To our knowledge, this is the largest reported outbreak of Brainerd diarrhea associated with a restaurant.

Aggregation of Adenovirus 2 in Source Water and Impacts on Disinfection by Chlorine.

It is generally accepted that viral particles in source water are likely to be found as aggregates attached to other particles. For this reason, it is important to investigate the disinfection efficacy of chlorine on aggregated viruses. A method to produce adenovirus particle aggregation was developed for this study. Negative stain electron microscopy was used to measure aggregation before and after addition of virus particles to surface water at different pH and specific conductance levels. The impact of aggregation on the efficacy of chlorine disinfection was also examined. Disinfection experiments with human adenovirus 2 (HAdV2) in source water were conducted using 0.2 mg/L free chlorine at 5 °C. Aggregation of HAdV2 in source water (≥3 aggregated particles) remained higher at higher specific conductance and pH levels. However, aggregation was highly variable, with the percentage of particles present in aggregates ranging from 43 to 71 %. Upon addition into source water, the aggregation percentage dropped dramatically. On average, chlorination CT values (chlorine concentration in mg/L × time in min) for 3-log10 inactivation of aggregated HAdV2 were up to three times higher than those for dispersed HAdV2, indicating that aggregation reduced the disinfection rate. This information can be used by water utilities and regulators to guide decision making regarding disinfection of viruses in water.