scholarly journals An Advanced Risk Modeling Method to Estimate Legionellosis Risks Within a Diverse Population

Water ◽  
2019 ◽  
Vol 12 (1) ◽  
pp. 43
Author(s):  
Mark H. Weir ◽  
Alexis L. Mraz ◽  
Jade Mitchell
Keyword(s):  
Legionella Pneumophila ◽  
Accurate Method ◽  
Incidence Rates ◽  
Quantitative Microbial Risk Assessment ◽  
Risk Modeling ◽  
Microbial Risk Assessment ◽  
Homogeneity Assumption ◽  
Life Years ◽  
Significant Difference ◽  
Legionnaires Disease

Quantitative microbial risk assessment (QMRA) is a computational science leveraged to optimize infectious disease controls at both population and individual levels. Often, diverse populations will have different health risks based on a population’s susceptibility or outcome severity due to heterogeneity within the host. Unfortunately, due to a host homogeneity assumption in the microbial dose-response models’ derivation, the current QMRA method of modeling exposure volume heterogeneity is not an accurate method for pathogens such as Legionella pneumophila. Therefore, a new method to model within-group heterogeneity is needed. The method developed in this research uses USA national incidence rates from the Centers for Disease Control and Prevention (CDC) to calculate proxies for the morbidity ratio that are descriptive of the within-group variability. From these proxies, an example QMRA model is developed to demonstrate their use. This method makes the QMRA results more representative of clinical outcomes and increases population-specific precision. Further, the risks estimated demonstrate a significant difference between demographic groups known to have heterogeneous health outcomes after infection. The method both improves fidelity to the real health impacts resulting from L. pneumophila infection and allows for the estimation of severe disability-adjusted life years (DALYs) for Legionnaires’ disease, moderate DALYs for Pontiac fever, and post-acute DALYs for sequela after recovering from Legionnaires’ disease.

scholarly journals Legionella pneumophila as a Health Hazard to Miners: A Pilot Study of Water Quality and QMRA

Water ◽  
2019 ◽  
Vol 11 (8) ◽  
pp. 1528
Author(s):  
Valerie Madera-García ◽  
Alexis L. Mraz ◽  
Nicolás López-Gálvez ◽  
Mark H. Weir ◽  
James Werner ◽  
...  
Keyword(s):  
Legionella Pneumophila ◽  
Health Hazard ◽  
Ventilation System ◽  
Sprinkler System ◽  
Dust Control ◽  
Quantitative Microbial Risk Assessment ◽  
Mining Operations ◽  
Microbial Risk Assessment ◽  
Microbial Risk ◽  
Life Years

Legionella pneumophila (L. pneumophila), the causative agent of legionellosis, is an aquatic bacterium that grows in warm water. Humans are only presented with a health risk when aerosolized water containing L. pneumophila is inhaled. In mining operations, aerosolized water is used as dust control and as part of the drilling operations, a currently ignored exposure route. This study characterized L. pneumophila concentrations in the mine’s non-potable water and the relationship between L. pneumophila and chlorine concentrations. These concentrations informed a quantitative microbial risk assessment (QMRA) model to estimate the infection risk to miners exposed to aerosolized water containing L. pneumophila. Fourteen water samples were collected from seven locations at a mine and analyzed for temperature, pH, chlorine, and L. pneumophila serogroup. Most samples (93%) tested positive for L. pneumophila cells. The faucet from the sprinkler system on the adit level (entrance to the underground mine levels) showed the highest concentration of L. pneumophila (8.35 × 104 MPN/L). Disability adjusted life years (DALYs) were estimated in the QMRA model and showed that the risk for all miners was significantly lower (p < 0.0001) with the ventilation system on than when the system was off. Our study showed that the use of a ventilation system at the adit level of the mine reduced the risk of infection with aerosolized L. pneumophila.

scholarly journals Microbial risk assessment of local handling and use of human faeces

2006 ◽  
Vol 5 (1) ◽  
pp. 117-128 ◽  
Author(s):  
Caroline Schönning ◽  
Therese Westrell ◽  
Thor Axel Stenström ◽  
Karsten Arnbjerg-Nielsen ◽  
Arne Bernt Hasling ◽  
...  
Keyword(s):  
Risk Assessment ◽  
Incidence Rates ◽  
Quantitative Microbial Risk Assessment ◽  
Risk Of Infection ◽  
Accidental Ingestion ◽  
Storage Container ◽  
Microbial Risk Assessment ◽  
Microbial Risk ◽  
Local Use ◽  
Annual Risk

Dry urine-diverting toilets may be used in order to collect excreta for the utilisation of nutrients. A quantitative microbial risk assessment was conducted in order to evaluate the risks of transmission of infectious disease related to the local use of faeces as a fertiliser. The human exposures evaluated included accidental ingestion of small amounts of faeces, or a mixture of faeces and soil, while emptying the storage container and applying the material in the garden, during recreational stays to the garden, and during gardening. A range of pathogens representing various groups of microorganisms was considered. Results showed that 12-months' storage before use was sufficient for the inactivation of most pathogens to acceptable levels. When working or spending time in the garden the annual risk of infection by Ascaris was still slightly above 10-4 in these scenarios, although the incidence rate for Ascaris is very low in the population in question. Measures to further reduce the hygienic risks include longer storage, or treatment, of the faeces. The results can easily be extended to other regions with different incidence rates.

scholarly journals Quantitative Microbial Risk Analysis to evaluate health effects of interventions in the urban water system of Accra, Ghana

2010 ◽  
Vol 8 (3) ◽  
pp. 417-430 ◽  
Author(s):  
Herve Labite ◽  
Isabella Lunani ◽  
Peter van der Steen ◽  
Kala Vairavamoorthy ◽  
Pay Drechsel ◽  
...  
Keyword(s):  
Disease Burden ◽  
Water System ◽  
Reference Value ◽  
Urban Water ◽  
Quantitative Microbial Risk Assessment ◽  
Indicator Organisms ◽  
Microbial Risk Assessment ◽  
Microbial Risk ◽  
Urban Water System ◽  
Life Years

A quantitative microbial risk assessment was applied to evaluate the microbial risks of the Accra Urban Water System (AUWS). The exposure assessment was based on the count of indicator organisms in waste water from open roadside drains and in water and sand samples from the beach. The predicted total disease burden generated in a representative catchment of the AUWS (Odaw Catchment) was 36,329 Disability Adjusted Life Years (DALYs) per year, of which 12 and 88% are caused by, respectively, shortcomings in the water supply system and inappropriate sanitation. The DALYs per person per year were above the WHO reference value. The open roadside drain had the highest contribution to the disease burden. Of four possible interventions evaluated for health risk reduction, the highest efficiency in terms of DALYs averted per euro invested would be achieved by providing covers for the open roadside drains.

Early Radiographic and Tomographic Manifestations of Legionnaires' Disease

2017 ◽  
Vol 68 (3) ◽  
pp. 328-333 ◽  
Author(s):  
Rémi Poirier ◽  
Jean Rodrigue ◽  
Jasmin Villeneuve ◽  
Yves Lacasse
Keyword(s):  
Ct Scan ◽  
Legionella Pneumophila ◽  
Community Acquired Pneumonia ◽  
Chest Ct ◽  
Quebec City ◽  
Bacterial Origin ◽  
Increased Risk ◽  
Significant Difference ◽  
Legionnaires Disease ◽  
Chest Ct Scan

Purpose Legionnaires' disease (LD) may occur sporadically or in the course of outbreaks, where the typical radiological manifestations of the disease may better be delineated. We took advantage of a rare community-based epidemic of LD (181 patients) that occurred in 2012 in Quebec City, Canada, to describe the radiographic features of LD and compare the its tomographic presentation with that of community-acquired pneumonia caused by common bacteria other than Legionella pneumophila. Methods From the 181 individuals affected in the outbreak, we obtained the chest radiographs of 159 individuals (mean 63 ± 15 years of age) for detailed analysis; 33 patients had a computed tomography (CT) scan performed during the course of their illness. In a case-control study, we compared the CT scans of patients with LD with those of patients who had received a diagnosis of community-acquired pneumonia caused by a pathogen other than Legionella and confirmed by chest CT scan. Results Overall, LD most often presented as an airspace consolidation involving 1 of the lower lobes. Pleural effusion and mediastinal adenopathies were apparent only in a minority, whereas no pneumothorax or cavitation was noted. We did not find any significant difference in chest CT scan findings in patients with LD vs those with community-acquired pneumonia from other bacterial origin. No radiological finding was clearly associated with an increased risk of intensive care unit admission or mortality. Conclusions The early radiographic and tomographic manifestations of LD are nonspecific and similar to those found in community-acquired pneumonia from other bacterial origin.

scholarly journals Flushing of stagnant premise water systems after the COVID-19 shutdown can reduce infection risk by Legionella and Mycobacterium spp.

2020 ◽  
Author(s):  
Raymond M Hozalski ◽  
Timothy M LaPara ◽  
Xiaotian Zhao ◽  
Taegyu Kim ◽  
Michael B Waak ◽  
...  
Keyword(s):  
Legionella Pneumophila ◽  
Water Levels ◽  
Hot Water ◽  
Quantitative Microbial Risk Assessment ◽  
Opportunistic Pathogens ◽  
Bacterial Gene ◽  
Microbial Risk Assessment ◽  
Microbial Risk ◽  
Commercial Cultivation ◽  
Premise Plumbing

The unprecedented widespread closing of buildings due to the COVID-19 pandemic has allowed water to stagnate in premise plumbing systems, creating conditions that may facilitate the growth of opportunistic pathogens. In this study, we flushed and collected samples from showers in buildings that had been unoccupied for approximately two months and quantified Legionella pneumophila using a commercial cultivation-based assay. In addition, all bacteria, Legionella spp., L. pneumophila, L. pneumophila serogroup 1, non-tuberculous mycobacteria (NTM), and Mycobacterium avium complex (MAC) were analyzed using quantitative PCR (qPCR). Despite low or negligible total chlorine in the stagnant pre-flush water samples, L. pneumophila were not detected by either method; Legionella spp., NTM, and MAC, however, were widespread. Using quantitative microbial risk assessment (QMRA), estimated risks of clinical illness from exposure to legionella and MAC via showering were generally low, but the risk of subclinical infection via Legionella spp. could exceed a 10-7 daily risk threshold if just a small fraction (≥0.1 %) of those legionellae detected by qPCR are highly infectious. Flushing cold and hot water lines rapidly restored a total chlorine (as chloramine) residual and decreased all bacterial gene targets to building inlet water levels within 30 min. Following flushing, the chlorine residual rapidly dissipated and bacterial gene targets rebounded, approaching pre-flush concentrations after 6 to 7 days of stagnation. These results suggest that stagnant water in premise plumbing may contain elevated levels of opportunistic pathogens; flushing, however, can rapidly improve water quality and reduce the health risk but the improvement will be short-lived if building disuse persists.

scholarly journals Legionnaires' disease: evaluation of a quantitative microbial risk assessment model

2008 ◽  
Vol 6 (2) ◽  
pp. 149-166 ◽  
Author(s):  
Thomas W. Armstrong ◽  
Charles N. Haas
Keyword(s):  
Risk Assessment ◽  
Natural Waters ◽  
Hot Water ◽  
Assessment Model ◽  
Clinical Severity ◽  
Cooling Towers ◽  
Quantitative Microbial Risk Assessment ◽  
Microbial Risk Assessment ◽  
Microbial Risk ◽  
Legionnaires Disease

Background: The quantities of Legionella vary considerably from natural waters to water in contaminated domestic hot water supplies, whirlpool spas and cooling towers, with the risk for LD rising as the Legionella counts grow. We currently report the results from our Quantitative Microbial Risk Assessment (QMRA) model evaluation. We developed the LD QMRA model to better understand Legionella exposure risks. Methods: Using an animal data derived model for LD, we calculated risks from estimated exposures for a whirlpool spa outbreak, two hot spring spa outbreaks and compared the results to the reported LD risks. Results: The QMRA model shows agreement (generally less than an order of magnitude discrepancy) with the reported Legionnaires' disease sub-clinical severity infection, clinical severity infection, and mortality risks. Conclusions: The LD QMRA model may lead to risk based limits to supplement the current guidance on Legionella control in cooling towers, whirlpool spas and other potential exposure sources. The verification of QMRA for LD also suggests the techniques, given suitable animal model data, may be useful in quantifying human response to other airborne pathogens.

scholarly journals Association of Calcium Supplementation During Pregnancy with the Birth Weight of Single-Born Neonates in Rural Northwest China

2020 ◽  
Vol 4 (Supplement_2) ◽  
pp. 1106-1106
Author(s):  
Gao Xiangyu ◽  
Mi Baibing ◽  
Dang Shaonong ◽  
Yan Hong
Keyword(s):  
Birth Weight ◽  
Gestational Age ◽  
Regression Models ◽  
Calcium Supplementation ◽  
Northwest China ◽  
Incidence Rates ◽  
Shaanxi Province ◽  
Significant Difference ◽  
Birth Weight Percentile ◽  
Weight Percentile

Abstract Objectives To investigate the association of calcium supplementation during the pregnancy with the birth weight of single-born neonates. Methods The survey employed a multistage, stratified and random sampling to investigate 15–49 aged pregnant women in 2010 to 2013 in Shaanxi province. A self - designed questionnaire was utilized. Birth weight between the 10(th) and 90(th) percentile was classified as appropriate for gestational age(AGA) infants. Chi-square test and logistic regression models were conducted to evaluate the association of calcium supplementation with single-born neonatal birth weight. Results A total of 28,490 women was enrolled in this study, 17 349 (60.9%) of participants had calcium supplementation during pregnancy. The incidence rates of small and large gestational age infants were 13.5% and 8.3%, respectively. The study conducted that calcium supplementation had a statistically significant difference in SGA (birth weight percentile &lt;10) (P &lt; 0.01). After adjusting the regression models by confounding factors, we found that calcium supplementation was still protective towards SGA birth, the difference was statistically significant (OR = 0.89, 95% CI: 0.82–0.96, P &lt; 0.05), but there was no significant difference in the birth to LGA (birth weight percentile &lt;10). Conclusions Calcium supplementation during pregnancy reduced the risk of SGA, but was not associated with the birth of LGA. Funding Sources

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