Annual Risk Of Infection Research Articles

Cost Analysis and Health Risk Assessment of Wastewater Reuse from Secondary and Tertiary Wastewater Treatment Plants

Irrigation with reclaimed water is a widespread solution to coping with water scarcity, especially in the Middle East and North Africa (MENA) region. This paper presents a systematic evaluation approach of six treatment alternatives proposed for Alexandria WWTP in Egypt as an applied example. This approach evaluates the effluent quality and cubic meter price from the proposed treatment alternatives while managing the health risks associated with reclaimed water irrigation. Rotavirus, Salmonella, Giardia duodenalis, and Ascaris were studied as waterborne pathogens. A quantitative microbial risk assessment model was used for the estimation of annual infection risks. The exposure scenarios include farmers and vegetable consumers. Activated sludge provided the lowest costs; however, it gave the lowest efficiencies and highest health risks. On the other hand, the highest efficiency and lowest health risks were obtained by the membrane bioreactor. The resulting price of a cubic meter of treated wastewater, used in irrigation, ranged from 0.082 to 0.133 USD. Irrigation using tertiary-treated wastewater achieved the target infection risk for unrestricted irrigation without using advanced treatment facilities. The results of this study could give a comprehensive view of reusing wastewater to decision-makers to address both water and food poverty not only in Egypt but also in other countries in MENA with similar economic and agro-ecological conditions.

Decreased annual risk of tuberculosis infection in South Korean healthcare workers using interferon-gamma release assay between 1986 and 2005

BackgroundTuberculosis (TB) has been a major public health problem in South Korea. Although TB notification rate in Korea is gradually decreasing, still highest among the member countries of the Organization for Economic Cooperation and Development. To effectively control TB, understanding the TB epidemiology such as prevalence of latent tuberculosis infection (LTBI) and annual risk of TB infection (ARI) are important. This study aimed to identify the prevalence of LTBI and ARI among South Korean health care workers (HCWs) based on their interferon-gamma release assays (IGRA).MethodsThis was single center, cross-sectional retrospective study in a tertiary hospital in South Korea. We performed IGRA in HCWs between May 2017 and March 2018. We estimated ARI based on IGRA results. Logistic regression model was used to identify factors affecting IGRA positivity.ResultsA total of 3233 HCWs were analyzed. Median age of participants was 38.0 and female was predominant (72.6%). Overall positive rate of IGRA was 24.1% and IGRA positive rates age-group wise were 6.6%, 14.4%, 34.3%, and around 50% in the age groups 20s, 30s, 40s, and 50s and 60s, respectively. The ARIs was 0.26–1.35% between 1986 and 2005; rate of TB infection has gradually decreased in the last two decades. Multivariable analysis indicated that older age, healed TB lesion in x-ray, and male gender were risk factors for IGRA positivity, whereas working in high-risk TB departments was not.ConclusionsResults showed that ARI in South Korean HCWs gradually decreased over two decades, although LTBI remained prevalent. Our results suggest that the LTBI test result of HCWs might be greatly affected by age, rather than occupational exposure, in intermediate TB burden countries. Thus, careful interpretation considering the age structure is required.

Quantitative Microbial Risk Assessment of Antimicrobial Resistant and Susceptible Staphylococcus aureus in Reclaimed Wastewaters.

The annual risks of colonization, skin infection, bloodstream infection (BSI), and disease burden from exposures to antibiotic-resistant and susceptible Staphylococcus aureus (S. aureus) were estimated using quantitative microbial risk assessment (QMRA). We estimated the probability of nasal colonization after immersion in wastewater (WW) or greywater (GW) treated across a range of treatment alternatives and subsequent infection. Horizontal gene transfer was incorporated into the treatment model but had little effect on the predicted risk. The cumulative annual probability of infection (resulting from self-inoculation) was most sensitive to the treatment log10 reduction value (LRV), S. aureus concentration, and the newly calculated morbidity ratios and was below the health benchmark of 10-4 infections per person per year (ppy) given a treatment LRV of roughly 3.0. The predicted annual disability-adjusted life years (DALYs), which were dominated by BSI, were below the health benchmark of 10-6 DALYs ppy for resistant and susceptible S. aureus, given LRVs of 4.5 and 3.5, respectively. Thus, the estimated infection risks and disease burdens resulting from nasal colonization are below the relevant health benchmarks for risk-based, nonpotable, or potable reuse systems but possibly above for immersion in minimally treated GW or WW. Strain-specific data to characterize dose-response and concentration in WW are needed to substantiate the QMRA.

Estimating acceptable exposure time for bioaerosols emission in a wastewater treatment plant by reverse quantitative microbial risk assessment based on various risk benchmarks.

Populations exposed to bioaerosols over time in wastewater treatment plants (WWTPs) will be infected. Then, the reverse quantitative microbial risk assessment (QMRA) provides a quantitative framework for the estimation of acceptable exposure time to protect people from excessive exposure and then manage their health risk. In this study, the acceptable exposure time for staffs and visiting researchers exposed to S. aureus or E. coli bioaerosols emitted from aeration ponds in WWTPs was estimated and analyzed by Monte Carlo simulation-based reverse QMRA (using the 1E-4 pppy suggested by the US EPA or 1E-6 DALYs pppy suggested by the WHO as benchmarks). The 1E-3 and 1E-2 pppy were selected as a series of loose annual infection risk benchmarks to calculate a practical acceptable exposure time. The results showed that for the acceptable exposure time in each specific exposure scenario, the exposure of females was consistently 0.3-0.4 times longer than that of males; the exposure of staffs was 3.6-3.9 times shorter than that of visiting researchers; the exposures of populations in the rotating-disc aeration mode were consistently 6.3-6.6 and 2.8-3.1 times longer than those in the microporous aeration mode for S. aureus and E. coli bioaerosols, respectively. The acceptable exposure time with the use of personal protective equipment (PPE) was 33.4-35.0 times as long as that without PPE. The US EPA benchmark is stricter than the WHO benchmark with regard to the estimation of the acceptable exposure time of S. aureus or E. coli bioaerosols. The 1E-3 pppy is more appropriate and practical than the US EPA benchmark, but the 1E-2 pppy is notably too loose for health risk management. This research can assist managers of WWTPs to formulate a justified exposure time and develop applicable administrative and personal intervention strategies. The results can enrich the knowledge bases of reverse QMRA to elect a series of loose health-based target risk benchmarks for health risk management.

Using QMRA to understand possible exposure risks of SARS-CoV-2 from the water environment.

This study investigated the human risk of infection due to inadvertent ingestion of water during swimming in a river that receives SARS-CoV-2-containing effluent from a wastewater treatment plant (WWTP). A quantitative microbial risk assessment (QMRA) approach was applied for risk estimation using dose-response models (DRM) of different surrogate coronaviruses (SARS-CoV-1, MERS-CoV) and the virus responsible for most infectious respiratory illnesses (i.e., influenza A H5N1) due to the unavailability of DRM for SARS-CoV-2. The ratio of infectious concentration to genomic copies of SARS-CoV-2 is unknown and also unavailable for other coronaviruses. Therefore, literature-based information on enteric viruses was used for formulating the ratio used for QMRA, although it is acknowledged that identifying this information for SARS-CoV-2 is a priority, and in the absence of information specific to SARS-CoV-2, another coronavirus would be a preferable surrogate to the enteric viruses used here. The calculated concentration of ingested SARS-CoV-2 ranged between 4.6 × 10−7 and 80.5 genomic copies/dip (one swim = 32 mL). The risk of infection (> 9 × 10−12 to 5.8 × 10−1) was found to be > 1/10,000 annual risk of infection. Moreover, the study revealed that the risk estimation was largely dependent on the value of the molecular concentration of SARS-CoV-2 (gc/mL). Overall immediate attention is required for obtaining information on the (i) ratio of infectious virus to genomic copies, (ii) DRM for SARS-CoV-2, and (iii) virus reduction rate after treatment in the WWTPs. The QMRA structure used in present findings is helpful in analyzing and prioritizing upcoming health risks due to swimming performed in contaminated rivers during the COVID-19 outbreak.Graphical abstract Supplementary InformationThe online version contains supplementary material available at 10.1007/s11356-021-16188-0.

Exposure parameters and health risk of Cryptosporidium and Giardia in the recreational water activities for urban residents in China.

Knowledge gaps in the exposure parameters for recreational water activities make quantitative risk assessment related to water recreation difficult. Therefore, the annual exposure frequency and single exposure duration for the recreational water activities of residents from ten cities in the North and South of China were investigated. Questionnaire interviews were carried on recreational water activities comprising swimming (SW), boating (BA), playing in interactive fountains (PF), and watching fountains (WF). Quantitative microbial risk assessment for the exposure of urban residents to Cryptosporidium and Giardia was also performed. For the four recreational water activities, the participation rates of urban residents in SW and WF were higher than the others. For SW and BA, the mean annual exposure frequency and single exposure duration for males were significantly higher than those for females. PF and WF showed the opposite. The annual exposure frequency for above 35-year-old residents was higher than that for young residents (18-35 years). However, the single exposure duration for young residents was highest in SW, BA, and PF. The mean annual exposure frequency and single exposure duration for North China residents were higher than those for South China residents in all recreational water activities, except for SW. Overall, the annual exposure frequency and single exposure duration in recreational water activities for all urban residents followed a lognormal distribution. In the four recreational water activities, the total annual infection risk of male exposure to Cryptosporidium was 1.0 × 10-2, with the confidence intervals between 95 and 5% of [4.3 × 10-4, 3.7 × 10-2], whereas that for females was 6.8 × 10-3 and [4.2 × 10-4, 2.4 × 10-2]. Also, the annual infection risk of males to Giardia was 8.8 × 10-3 and [5.1×10-4, 3.2×10-2], and that of females was 5.3 × 10-3 and [4.0 × 10-4, 1.8 × 10-2]. These results demonstrated that SW and PF made the highest contribution to the total annual infection risk. Sensitivity analysis highlighted that the characterization of exposure parameters plays a critical role in health risk assessment, which may provide a scientific basis for recreational water quality standards formulation.

Human Pathogenic Bacteria Detected in Rainwater: Risk Assessment and Correlation to Microbial Source Tracking Markers and Traditional Indicators.

Roof-harvested rainwater (RHRW) was investigated for the presence of the human pathogenic bacteria Mycobacterium tuberculosis (M. tuberculosis), Yersinia spp. and Listeria monocytogenes (L. monocytogenes). While Yersinia spp. were detected in 92% (n = 25) of the RHRW samples, and L. monocytogenes and M. tuberculosis were detected in 100% (n = 25) of the samples, a significantly higher mean concentration (1.4 × 103 cells/100 mL) was recorded for L. monocytogenes over the sampling period. As the identification of appropriate water quality indicators is crucial to ensure access to safe water sources, correlation of the pathogens to traditional indicator organisms [Escherichia coli (E. coli) and Enterococcus spp.] and microbial source tracking (MST) markers (Bacteroides HF183, adenovirus and Lachnospiraceae) was conducted. A significant positive correlation was then recorded for E. coli versus L. monocytogenes (r = 0.6738; p = 0.000), and Enterococcus spp. versus the Bacteroides HF183 marker (r = 0.4071; p = 0.043), while a significant negative correlation was observed for M. tuberculosis versus the Bacteroides HF183 marker (r = −0.4558; p = 0.022). Quantitative microbial risk assessment indicated that the mean annual risk of infection posed by L. monocytogenes in the RHRW samples exceeded the annual infection risk benchmark limit (1 × 10–4 infections per person per year) for intentional drinking (∼10–4). In comparison, the mean annual risk of infection posed by E. coli was exceeded for intentional drinking (∼10–1), accidental consumption (∼10–3) and cleaning of the home (∼10–3). However, while the risk posed by M. tuberculosis for the two relevant exposure scenarios [garden hosing (∼10–5) and washing laundry by hand (∼10–5)] was below the benchmark limit, the risk posed by adenovirus for garden hosing (∼10–3) and washing laundry by hand (∼10–3) exceeded the benchmark limit. Thus, while the correlation analysis confirms that traditional indicators and MST markers should be used in combination to accurately monitor the pathogen-associated risk linked to the utilisation of RHRW, the integration of QMRA offers a more site-specific approach to monitor and estimate the human health risks associated with the use of RHRW.

Human Fecal Pollution Monitoring and Microbial Risk Assessment for Water Reuse Potential in a Coastal Industrial-Residential Mixed-Use Watershed.

Rapid economic development has caused industrial expansion into residential communities, leading to higher fecal pollution loads that could be discharged into aquatic environments. However, little is known regarding the potential microbial impact on human health. This study investigated microbial contamination from coastal industrial–residential community areas in nine sampling sites in waterways during three dry events. A general microbial source tracking (MST) marker, GenBac3, was detected in all samples from all three events, indicating continuing fecal pollution in the area, mostly from human sewage contamination. This was shown by the human-specific genetic marker crAssphage (88.9%) and human polyomavirus (HPyVs; 92.6%) detection. Enteric human adenovirus (HAdV40/41) showed three positive results only from residential sites in the first event. No spatial difference was observed for MST markers and traditional fecal indicators (total coliforms and Escherichia coli) in each event. Still, a significantly lower abundance of GenBac3, HPyVs, and total coliforms in the first sampling event was detected. Spearman’s rho analysis indicated a strong correlation among certain pairs of microbial parameters. Multivariate analysis revealed two clusters of samples separated by land use type (industrial vs. residential). According to factor analysis of mixed data, the land use parameter was more associated with physicochemical parameters (i.e., salinity, conductivity, water temperature, and dissolved oxygen). A Quantitative Microbial Risk Assessment (QMRA) was then conducted to estimate the annual infection risks of HAdV40/41 for non-potable water reuse purposes using predicted concentrations from crAssphage and HPyVs. The highest risks (95th percentiles) were ranked by food crop irrigation, aquaculture, and toilet flushing, at 10–1, 10–2, and 10–3 per person per year (pppy). Required treatment levels to achieve a 10–4 pppy annual infection risk were estimated. QMRA-based water treatment scenarios were suggested, including chlorination for toilet flushing reuse and depth filtration prior to chlorination for aquaculture and food crop irrigation. Microbial monitoring combined with a QMRA could provide better insights into fecal pollution patterns and the associated risks, facilitating effective water quality management and appropriate prior treatments for water reuse.

Microbiological Health Risk Assessment of Water Conservation Strategies: A Case Study in Amsterdam.

The aim of this study was to assess the health risks that may arise from the implementation of greywater reuse and rainwater harvesting for household use, especially for toilet flushing. In addition, the risk of cross connections between these systems and the drinking water system was considered. Quantitative microbial risk assessment (QMRA) is a method that uses mathematical modelling to estimate the risk of infection when exposure to pathogens happens and was used in this study to assess the health risks. The results showed that using rainwater without prior treatment for toilet flushing poses an annual infection risk from L. pneumophila at 0.64 per-person-per-year (pppy) which exceeds the Dutch standard of 10−4 pppy. The use of untreated greywater showed a risk that is below the standard. However, treatment is recommended due to the ability of P. aeruginosa to grow in the reuse system. Moreover, showering and drinking with cross-connected water has a high annual infection risk that exceeds the standard due to contact with Staphylococcus aureus and E. coli O157:H7. Several measures can be implemented to mitigate the risks such as treating the greywater and rainwater with a minimum of 5-log removal, closing the toilet lid while flushing, good design of greywater and rainwater collection systems, and rigorous plumbing installation procedures.

COVID-19 infection risk from exposure to aerosols of wastewater treatment plants

Fecal shedding of SARS-CoV-2 from COVID-19 patients and presence of the viral RNA in wastewater have extensively been reported. Some wastewater treatment plant (WWTP) processes generate aerosols which have the potential to transmit pathogenic microorganisms and present a health risk for exposed individuals. We analyzed the presence of viral RNA of SARS-CoV-2 in raw wastewater and air samples of WWTPs. The risk that may arise from exposure to virus-contaminated aerosols of wastewater was estimated by developing a quantitative microbial risk analysis (QMRA) method. SARS-CoV-2 was detected in 9 of 24 (37.5%) wastewater samples with a concentration about 104 genomic copies L−1. The viral RNA was also detected in 40% (6/15) of air samples. QMRA analysis showed a relatively high risk of SARS-CoV-2 infection for wastewater workers via exposure to the viral aerosols. The estimated annual infection risk ranged from 1.1 × 10−2 to 2.3 × 10−2 per person per year (PPPY) for wastewater workers which was higher than the reference level recommended by WHO (10−3 pppy). However, due to the lack of data on survival of SARS-CoV-2 in wastewater and its fate in aerosolized state, more research is needed to determine the importance of wastewater in transmission of COVID-19.

Quantitative Microbial Risk Assessment of Pediatric Infections Attributable to Ingestion of Fecally Contaminated Domestic Soils in Low-Income Urban Maputo, Mozambique.

Rigorous studies of water, sanitation, and hygiene interventions in low- and middle-income countries (LMICs) suggest that children are exposed to enteric pathogens via multiple interacting pathways, including soil ingestion. In 30 compounds (household clusters) in low-income urban Maputo, Mozambique, we cultured Escherichia coli and quantified gene targets from soils (E. coli: ybbW, Shigella/enteroinvasiveE. coli (EIEC): ipaH, Giardia duodenalis: β-giardin) using droplet digital PCR at three compound locations (latrine entrance, solid waste area, dishwashing area). We found that 88% of samples were positive for culturable E. coli (mean = 3.2 log10 CFUs per gram of dry soil), 100% for molecular E. coli (mean = 5.9 log10 gene copies per gram of dry soil), 44% for ipaH (mean = 2.5 log10), and 41% for β-giardin (mean = 2.1 log10). Performing stochastic quantitative microbial risk assessment using soil ingestion parameters from an LMIC setting for children 12–23 months old, we estimated that the median annual infection risk by G. duodenalis was 7100-fold (71% annual infection risk) and by Shigella/EIEC was 4000-fold (40% annual infection risk) greater than the EPA’s standard for drinking water. Compounds in Maputo, and similar settings, require contact and source control strategies to reduce the ingestion of contaminated soil and achieve acceptable levels of risk.

Sanitation By-Products Used for Lettuce (<i>Lactuca sativa</i> L.) Production: Quantitative Microbial Risk Assessment

Sanitation by-products (i.e. greywater, human urine and toilet compost) reuse for agriculture presents an opportunity to enhance food security while overcoming water scarcity and fertilizers issues in developing countries. However, the risks to health from farmers and consumers’ exposure to pathogenic micro-organisms persistent in sanitation by-products has hindered their popularity in these regions. This study was conducted to apply a quantitative microbial risk assessment to estimate the annual risk probability of Salmonella infection associated with these sanitation by-products reuse for lettuce production and explore options for health risk reduction. Risk was performed a Monte Carlo simulation for farmers and consumers. The exposure routes were contaminated soil ingestion, urine/greywater/compost ingestion and lettuce consumption without washing. Results showed that the annual infection risks of Salmonella through ingestion contaminated soil associated with urine and compost were typical scenario: 9.04 × per-person-per-year (pppy) and 2.97 × pppy, respectively, are higher than the WHO benchmark (≤1.0 × pppy). Conversely, those contaminated from greywater were 6.83 × pppy are meet the WHO benchmark. On the other hand, annual risks through lettuce consumption fertilized with urine (1.20 × pppy) were less than the risks from compost (6.20 × pppy) and greywater (7.76 × pppy). Moreover, the annual risks of infection from greywater ingestion (1.77 × pppy) exhibits a much higher risk than that urine ingestion (6.20 × pppy) approximately two orders of magnitude, and which are higher than the WHO tolerable limit of risk. The risk assessment outcomes of using sanitation by-products to lettuce production should be promoted with proper awareness of the risk by farmers and consumers.

Vibrio cholerae O1 transmission in Bangladesh: insights from a nationally representative serosurvey

SummaryBackgroundPandemic Vibrio cholerae from cholera-endemic countries around the Bay of Bengal regularly seed epidemics globally. Without reducing cholera in these countries, including Bangladesh, global cholera control might never be achieved. Little is known about the geographical distribution and magnitude of V cholerae O1 transmission nationally. We aimed to describe infection risk across Bangladesh, making use of advances in cholera seroepidemiology, therefore overcoming many of the limitations of current clinic-based surveillance.MethodsWe tested serum samples from a nationally representative serosurvey in Bangladesh with eight V cholerae-specific assays. Using these data with a machine-learning model previously validated within a cohort of confirmed cholera cases and their household contacts, we estimated the proportion of the population with evidence of infection by V cholerae O1 in the previous year (annual seroincidence) and used Bayesian geostatistical models to create high-resolution national maps of infection risk.FindingsBetween Oct 16, 2015, and Jan 24, 2016, we obtained and tested serum samples from 2930 participants (707 households) in 70 communities across Bangladesh. We estimated national annual seroincidence of V cholerae O1 infection of 17·3% (95% CI 10·5–24·1). Our high-resolution maps showed large heterogeneity of infection risk, with community-level annual infection risk within the sampled population ranging from 4·3% to 62·9%. Across Bangladesh, we estimated that 28·1 (95% CI 17·1–39·2) million infections occurred in the year before the survey. Despite having an annual seroincidence of V cholerae O1 infection lower than much of Bangladesh, Dhaka (the capital of Bangladesh and largest city in the country) had 2·0 (95% CI 0·6–3·9) million infections during the same year, primarily because of its large population.InterpretationSerosurveillance provides an avenue for identifying areas with high V cholerae O1 transmission and investigating key risk factors for infection across geographical scales. Serosurveillance could serve as an important method for countries to plan and monitor progress towards 2030 cholera elimination goals.FundingThe Bill & Melinda Gates Foundation, National Institutes of Health, and US Centers for Disease Control and Prevention.

Evaluation of recreational risks due to exposure of antibiotic-resistance bacteria from environmental water: A proposed framework

This research provides a framework for the human health risk assessment due to exposure of AR (antibiotic resistance) E. coli from recreational water (swimming activity). Literature-based epidemiological studies were used for f-value formulation (i.e., AR E. coli/total number of E. coli isolates) and the theoretical calculation of AR and non-AR E. coli concentrations. Risk was estimated using calculated values by considering four different dose-response (D-R) scenarios with known characteristics due to current lack of availability of D-R for AR bacteria. f-values ranged between 0.14 and 0.59 and the order of calculated theoretical values of maximum AR E. coli are as follows: ampicillin or amoxicillin (38 CFU/dip) > co-trimoxazole (19 CFU/dip) ~ tetracycline (18 CFU/dip) > ceftriaxone or cefotaxime or ceftazidime (10 CFU/dip) ~ ciprofloxacin or ofloxacin (9 CFU/dip). The risk of infection was considerably high for theoretical calculated concentration values regardless of the chosen D-R model (annual risk of infection (95th percentile) = 1, Spearman's rank correlation coefficient = −0.06 to 0.94), under the conditions studied. Further, AR levels of human gastrointestinal-tract were determined using literature-reported data in stool samples and indicated that the resistance level was very high in healthy human (range: 3.7 × 107–8.4 × 107 CFU/g of wet lumen content). The maximum allowable concentration values for AR E. coli and non-ARB (0.0075 CFU/dip and 2.56 CFU/dip) were found to be smaller than the USEPA recreational water quality guidelines (≤126 CFU/100 mL), which can help the USEPA and other regulatory bodies in revisiting the current guidelines. So based on the noted results, we can conclude that the maintenance of inventory of actual measured concentration of ARB in the recreational water sites is needed to prevent unwanted complication related to the treatment of infectious sustained by resistant microbes.

Health Risks and Potential Sources of Contamination of Groundwater Used by Public Schools in Vhuronga 1, Limpopo Province, South Africa.

Public schools in most rural areas of South Africa depend on untreated groundwater due to unreliable water supply by the municipalities. This has the potential to cause water-related health problems to school children. Temperature, pH, and electrical conductivity (EC) were measured in situ. Chemical (fluoride, chloride, sulphate, phosphate, nitrate, magnesium, calcium, sodium, and potassium) and microbial (Escherichia coliform (E. coli), Salmonella typhimurium, and Shigella flexneri) water quality parameters were analysed in groundwater samples from 10 public schools in Vhuronga 1 to determine suitability for use. Quantitative microbial risk assessment was carried out to determine risks of infection and illness due to consumption of groundwater. Correlation analysis was used to identify potential sources of contamination. All physical and most chemical water quality parameters were within guidelines for domestic water use. A high proportion of schools had high levels of microbial organisms. Risks of infection per day were relatively low for all schools. The annual risks of infection due to E. coli and Shigella flexneri for most schools was high, with maximum values of 89.11 and 83.75%, respectively. Maximum risks of illness per year were 31.19, 30.37, and 29.31% for E. coli, Salmonella typhimurium, and Shigella flexneri, respectively. Correlation analysis indicated potential contamination of groundwater by agricultural activities, domestic waste, and faecal contamination from pit latrines. Preventive and mitigation measures to minimise such risks, including locating boreholes at safe distances from pit latrines, prevention/minimisation of pollution of groundwater from agricultural activities, and point-of-use treatment of groundwater by the schools are therefore essential.

Tuberculosis Infection in Women of Reproductive Age: A Cross-sectional Study at Antenatal Care Clinics in an Ethiopian City.

BackgroundKnowledge on tuberculosis (TB) infection epidemiology in women of reproductive age living in TB-endemic areas is limited. We used a composite definition of TB infection in a cohort of pregnant women recruited in an Ethiopian city as a model for TB exposure patterns, and to identify factors associated with TB infection. MethodsWomen seeking antenatal care at public health facilities underwent structured interviews, physical examination, and QuantiFERON-TB Gold-Plus (QFT) testing. Women with symptoms compatible with TB disease, and all human immunodeficiency virus (HIV)–positive women, were investigated for active TB by sputum bacteriological testing. TB infection (TB+) was defined as either positive QFT (≥ 0.35 IU/mL), self-reported previous active TB, or current active TB. Associations between TB infection and clinical, demographic, and socioeconomic characteristics were tested in multiple logistic regression analysis.ResultsAmong 1834 participants, 679 (37.0%) met criteria for TB+ (80 [4.4%] previous active TB, 5 [0.3%] current active TB, and 594 [32.4%] QFT-positive without previous or current active TB). Age (annual adjusted odds ratio [AOR], 1.069 [95% confidence interval {CI}, 1.045–1.093]) and HIV infection (AOR, 1.43 [95% CI, 1.033–1.988]) were independently associated with TB+. The relationship with increasing age was only observed in HIV-negative women, and translated to an estimated annual risk of TB infection of 2.1% in HIV-negative women.ConclusionsTB infection in women of reproductive age in Ethiopia was independently associated with HIV infection and increasing age, suggesting exposure to contagious TB and continuous acquisition of TB infection in this population.

A risk-based evaluation of onsite, non-potable reuse systems developed in compliance with conventional water quality measures.

Water quality standards (WQSs) based on water quality measures (e.g., fecal indicator bacteria (FIB)) have been used by regulatory agencies to assess onsite, non-potable water reuse systems. A risk-based approach, based on quantitative microbial risk assessment, was developed to define treatment requirements that achieve benchmark levels of risk. This work compared these approaches using the predicted annual infection risks for non-potable reuse systems that comply with WQSs along with the benchmark risk levels achieved by the risk-based systems. The systems include a recirculating synthetic sand filter or an aerobic membrane bioreactor (MBR) combined with disinfection. The greywater MBR system had predicted risks in the range of the selected benchmark levels. However, wastewater reuse with systems that comply with WQSs had uncertain and potentially high predicted risks (i.e., >10-2 infections per person per year) in residential applications, due to exposures to viruses and protozoa. The predicted risks illustrate that WQSs based on FIB treatment performance do not ensure adequate treatment removal of viruses and protozoa. We present risk-based log10 pathogen reduction targets for intermediate-sized non-potable systems, which are 0.5 log10 less than those previously proposed for district-sized systems. Still, pathogen treatment performance data are required to better manage non-potable reuse risk.

High Rates of Recurrent Tuberculosis Disease: A Population-level Cohort Study.

BackgroundRetreatment tuberculosis (TB) disease is common in high-prevalence settings. The risk of repeated episodes of recurrent TB is unknown. We calculated the rate of recurrent TB per subsequent episode by matching individual treatment episodes over a period of 13 years.MethodsAll recorded TB episodes in Cape Town between 2003 and 2016 were matched by probabilistic linkage of personal identifiers. Among individuals with a first episode notified in Cape Town and who completed their prior treatment successfully we estimated the recurrence rate stratified by subsequent episode and HIV status. We adjusted person-time to background mortality by age, sex, and HIV status.ResultsA total of 292 915 TB episodes among 263 848 individuals were included. The rate of recurrent TB was 16.4 per 1000 person-years (95% CI, 16.2–16.6), and increased per subsequent episode (8.4-fold increase, from 14.6 to 122.7 per 1000 from episode 2 to 6, respectively). These increases were similar stratified by HIV status. Rates among HIV positives were higher than among HIV negatives for episodes 2 and 3 (2- and 1.5-fold higher, respectively), and the same thereafter.ConclusionsTB recurrence rates were high and increased per subsequent episode, independent of HIV status. This suggests that HIV infection is insufficient to explain the high burden of recurrence; it is more likely due to a high annual risk of infection combined with an increased risk of infection or progression to disease associated with a previous TB episode. The very high recurrence rates would justify increased TB surveillance of patients with >1 episode.

The annual risk of tuberculosis infection in newly hired researchers and healthcare workers using interferon-gamma release assay in Japan

The tuberculosis (TB) notification rate in Japan is gradually decreasing but has not yet achieved “pre-elimination,” defined by the World Health Organization. To effectively tackle, control, and eliminate TB, estimating and monitoring the annual risk of TB infection (ARI) using tuberculin skin testing (TST) to understand the dynamics of TB epidemiology are significantly important. However, studies estimating ARIs using TST are few considering that Bacillus Calmette-Guérin vaccination coverage is high in Japan. This was a single-center, cross-sectional study conducted between January 2011 and December 2018 in Tokyo area where interferon-gamma release assays (IGRAs) were performed in newly hired researchers of Keio University School of Medicine and healthcare workers of Keio University Hospital to determine TB infection. We estimated the prevalence of TB infection and ARI based on their IGRA results. Among the 3908 subjects, 83 (2.124%) had positive IGRA results. Multiple logistic regression analysis revealed that age was a significant risk factor for positive IGRA result (adjusted odds ratio, 1.046). The ARIs were 0.049%–0.156% between 1986 and 2004, midyears of TB infection, but have not significantly decreased over approximately two decades. To decrease the risk of TB infection, advanced strategies to control and eliminate TB in Tokyo area are significantly required.

Effect of disinfectant residuals on infection risks from Legionella pneumophila released by biofilms grown under simulated premise plumbing conditions

The ubiquitous presence of biofilms in premise plumbing and stagnation, which commonly occurs in premise plumbing, can exacerbate the decay of chlorine residual in drinking water. Using biofilms grown in a simulated premise plumbing setup fed directly with freshly treated water at two full-scale water treatment plants, we previously determined the mass transfer coefficients for chlorine decay in premise plumbing. These coefficients coupled with inactivation kinetics of L. pneumophila released from biofilms reported previously were integrated into a Monte Carlo framework to estimate the infection risk of biofilm-derived L. pneumophila from 1 to 48 h of stagnation. The annual infection risk was significantly higher when water stayed stagnant for up to 48 h in pipes covered internally with biofilms, compared to clean pipes without biofilms. The decay of residual chlorine due to biofilms during 48-hour stagnation led to up to 6 times increase in the annual infection risk compared to the case where biofilms was absent. Global sensitivity analysis revealed that the rate of L. pneumophila detachment from biofilms and the decay of chlorine residual during stagnation are the two most important factors influencing the infection risks. Stagnation caused by water use patterns and water-saving devices in the premise plumbing can lead to increased infection risk by biofilm-derived L. pneumophila. Overall, this study’s findings suggested that biofilms could induce chlorine decay and consequently increase L. pneumophila infection risk. Thus, reducing stagnation, maintaining residual chlorine, and suppressing biofilm growth could contribute to better management of L. pneumophila infection risk.