Estimating the burden of illness caused by domestic waterborne Legionnaires' disease in Canada: 2015-2019.

Legionellosis is a disease caused by the bacterium Legionella that most commonly presents as Legionnaires' disease (LD), a severe form of pneumonia. From 2015 to 2019, an average of 438 LD cases per year were reported in Canada. However, it is believed that the actual number of cases is much higher, since LD may be underdiagnosed and underreported. The purpose of this study was to develop an estimate of the true incidence of illnesses, hospitalizations, and deaths associated with LD in Canada. Values were derived using a stochastic model, based on Canadian surveillance data from 2015 to 2019, which were scaled up to account for underdiagnosis and underreporting. Overall, there were an estimated 1,113 (90% CrI: 737-1,730) illnesses, 1,008 (90% CrI: 271-2,244) hospitalizations, and 34 (90% CrI: 4-86) deaths due to domestically acquired waterborne LD annually in Canada from 2015 to 2019. It was further estimated that only 36% of illnesses and 39% of hospitalizations and deaths were captured in surveillance, and that 22% of illnesses were caused by Legionella serogroups and species other than Legionella pneumophila serogroup 1 (non-Lp1). This study highlights the true burden and areas for improvement in Canada's surveillance and detection of LD.

An application for relating Legionella shower water monitoring results to estimated health outcomes.

Exposure models are useful tools for relating environmental monitoring data to expected health outcomes. The objective of this study was to (1) compare two Legionella shower exposure models, and (2) develop a risk calculator tool for relating environmental monitoring data to estimated Legionella infection risks and Legionnaires' Disease (LD) illness risks. Legionella infection risks for a single shower event were compared using two shower Legionella exposure models. These models varied in their description of partitioning of Legionella in aerosols and aerosol deposition in the lung, where Model 1 had larger and fewer aerosol ranges than Model 2. Model 2 described conventional vs. water efficient showers separately, while Model 1 described exposure for an unspecified shower type (did not describe it as conventional or water efficient). A Monte Carlo approach was used to account for variability and uncertainty in these aerosolization and deposition parameters, Legionella concentrations, and the dose-response parameter. Methods for relating infection risks to illness risks accounting for demographic differences were used to inform the risk calculator web application ("app"). Model 2 consistently estimated higher infection risks than Model 1 for the same Legionella concentration in water and estimated deposited doses with less variability. For a 7.8-min shower with a Legionella concentration of 0.1 CFU/mL, the average infection risks estimated using Model 2 were 4.8 × 10-6 (SD=3.0 × 10-6) (conventional shower) and 2.3 × 10-6 (SD=1.7 × 10-6) (water efficient). Average infection risk estimated by Model 1 was 1.1 × 10-6 (SD=9.7 × 10-7). Model 2 was used for app development due to more conservative risk estimates and less variability in estimated dose. While multiple Legionella shower models are available for quantitative microbial risk assessments (QMRAs), they may yield notably different infection risks for the same environmental microbial concentration. Model comparisons will inform decisions regarding their integration with risk assessment tools. The development of risk calculator tools for relating environmental microbiology data to infection risks will increase the impact of exposure models for informing water treatment decisions and achieving risk targets.

Economic Burden of Legionnaires' Disease, United States, 2014.

Through the use of published estimates of medical costs and new calculations of productivity losses, we estimate the lifetime economic burden of 2014 Legionnaires' disease cases in the United States at ≈$835 million. This total includes $21 million in productivity losses caused by absenteeism and $412 million in productivity losses caused by premature deaths.

Population-Based Assessment of Clinical Risk Factors for Legionnaires' Disease.

We used US population-based surveillance data to characterize clinical risk factors for Legionnaires' disease (LD). The LD incidence increased by age and the risk was elevated for 12 clinical conditions, when compared to healthy adults. This information can be used to guide testing, treatment, and public health prevention efforts.

Multiple Sources of the Outbreak of Legionnaires' Disease in Genesee County, Michigan, in 2014 and 2015.

BACKGROUND: A community-wide outbreak of Legionnaires' disease (LD) occurred in Genesee County, Michigan, in 2014 and 2015. Previous reports about the outbreak are conflicting and have associated the outbreak with a change of water source in the city of Flint and, alternatively, to a Flint hospital. OBJECTIVE: The objective of this investigation was to independently identify relevant sources of Legionella pneumophila that likely resulted in the outbreak. METHODS: An independent, retrospective investigation of the outbreak was conducted, making use of public health, health care, and environmental data and whole-genome multilocus sequence typing (wgMLST) of clinical and environmental isolates. RESULTS: Strong evidence was found for a hospital-associated outbreak in both 2014 and 2015: a) 49% of cases had prior exposure to Flint hospital A, significantly higher than expected from Medicare admissions; b) hospital plumbing contained high levels of L. pneumophila; c) Legionella control measures in hospital plumbing aligned with subsidence of hospital A-associated cases; and d) wgMLST showed Legionella isolates from cases exposed to hospital A and from hospital plumbing to be highly similar. Multivariate analysis showed an increased risk of LD in 2014 for people residing in a home that received Flint water or was located in proximity to several Flint cooling towers. DISCUSSION: This is the first LD outbreak in the United States with evidence for three sources (in 2014): a) exposure to hospital A, b) receiving Flint water at home, and c) residential proximity to cooling towers; however, for 2015, evidence points to hospital A only. Each source could be associated with only a proportion of cases. A focus on a single source may have delayed recognition and remediation of other significant sources of L. pneumophila. https://doi.org/10.1289/EHP5663.

Legionella spp. Risk Assessment in Recreational and Garden Areas of Hotels.

Several Travel-associated Legionnaires' disease (TALD) cases occur annually in Europe. Except from the most obvious sites (cooling towers and hot water systems), infections can also be associated with recreational, water feature, and garden areas of hotels. This argument is of great interest to better comprehend the colonization and to calculate the risk to human health of these sites. From July 2000-November 2017, the public health authorities of the Island of Crete (Greece) inspected 119 hotels associated with TALD, as reported through the European Legionnaires' Disease Surveillance Network. Five hundred and eighteen samples were collected from decorative fountain ponds, showers near pools and spas, swimming pools, spa pools, garden sprinklers, drip irrigation systems (reclaimed water) and soil. Of those, 67 (12.93%), originating from 43 (35.83%) hotels, tested positive for Legionella (Legionella pneumophila serogroups 1, 2, 3, 6, 7, 8, 13, 14, 15 and non-pneumophila species (L. anisa, L. erythra, L. taurinensis, L. birminghamensis, L. rubrilucens). A Relative Risk (R.R.) > 1 (p < 0.0001) was calculated for chlorine concentrations of less than 0.2 mg/L (R.R.: 54.78), star classification (<4) (R.R.: 4.75) and absence of Water Safety Plan implementation (R.R.: 3.96). High risk (≥104 CFU/L) was estimated for pool showers (16.42%), garden sprinklers (7.46%) and pool water (5.97%).

Assessment of the Legionnaires' disease outbreak in Flint, Michigan.

The 2014-2015 Legionnaires' disease (LD) outbreak in Genesee County, MI, and the outbreak resolution in 2016 coincided with changes in the source of drinking water to Flint's municipal water system. Following the switch in water supply from Detroit to Flint River water, the odds of a Flint resident presenting with LD increased 6.3-fold (95% CI: 2.5, 14.0). This risk subsided following boil water advisories, likely due to residents avoiding water, and returned to historically normal levels with the switch back in water supply. During the crisis, as the concentration of free chlorine in water delivered to Flint residents decreased, their risk of acquiring LD increased. When the average weekly chlorine level in a census tract was <0.5 mg/L or <0.2 mg/L, the odds of an LD case presenting from a Flint neighborhood increased by a factor of 2.9 (95% CI: 1.4, 6.3) or 3.9 (95% CI: 1.8, 8.7), respectively. During the switch, the risk of a Flint neighborhood having a case of LD increased by 80% per 1 mg/L decrease in free chlorine, as calculated from the extensive variation in chlorine observed. In communities adjacent to Flint, the probability of LD occurring increased with the flow of commuters into Flint. Together, the results support the hypothesis that a system-wide proliferation of legionellae was responsible for the LD outbreak in Genesee County, MI.

Legionnaires Disease Surveillance in US Department of Veterans Affairs Medical Facilities and Assessment of Health Care Facility Association.

Importance: Legionnaires disease (LD) incidence is increasing in the United States. Health care facilities are a high-risk setting for transmission of Legionella bacteria from building water systems to occupants. However, the contribution of LD in health care facilities to national LD rates is not well characterized. Objectives: To determine the burden of LD in US Department of Veterans Affairs (VA) patients and to assess the amount of LD with VA exposure. Design, Setting, and Participants: Retrospective cohort study of reported LD data in VA medical facilities in a national VA LD surveillance system from January 1, 2014, to December 31, 2016. The study population included total veteran enrollees and enrollees who used the VA health care system. Main Outcomes and Measures: The primary outcome was assessment of annual LD rates, categorized by VA and non-VA exposure. Legionnaires disease rates for cases with VA exposure were determined on both population and exposure potential levels. Rates by VA exposure potential were calculated using inpatient bed days of care, long-term care resident days, or outpatient encounters. In addition, types and amounts of LD diagnostic testing were calculated. Case and testing data were analyzed nationally and regionally. Results: There were 491 LD cases in the case report surveillance system from January 1, 2014, to December 31, 2016. Most cases (447 [91%]) had no VA exposure or only outpatient VA exposure. The remaining 44 cases had VA exposure from overnight stays. Total LD rates from January 1, 2014, to December 31, 2016, increased for all VA enrollees (from 1.5 to 2.0 per 100 000 enrollees; P = .04) and for users of VA health care (2.3 to 3.0 per 100 000 enrollees; P = .04). The LD rate for the subset who had no VA exposure also increased (0.90 to 1.47 per 100 000 enrollees; P < .001). In contrast, the LD rate for patients with VA overnight stay decreased on a population level (5.0 to 2.3 per 100 000 enrollees; P < .001) and an exposure level (0.31 to 0.15 per 100 000 enrollees; P < .001). Regionally, the eastern United States had the highest LD rates. The urine antigen test was the most used LD diagnostic method; 49 805 tests were performed in 2015-2016 with 335 positive results (0.67%). Conclusions and Relevance: Data in the VA LD databases showed an increase in overall LD rates over the 3 years, driven by increases in rates of non-VA LD. Inpatient VA-associated LD rates decreased, suggesting that the VA's LD prevention efforts have contributed to improved patient safety.

Clinical Utility of Testing for Legionella Pneumonia in Central Texas.

RATIONALE: Legionella pneumophila is an uncommon cause of community-acquired pneumonia in the south central region of the United States, and regular testing may not be cost effective in areas of low incidence. OBJECTIVES: To evaluate the incidence of Legionella in central Texas and to determine the cost effectiveness of Legionella urinary antigen testing. METHODS: We performed a single-center retrospective cohort study of patients admitted with pneumonia between January 2001 and December 2013. Patients were identified by Binax Legionella urinary antigen and International Classification of Disease, Ninth Revision codes. Demographic characteristics and clinical history of the confirmed Legionella pneumonia cases were obtained by chart review. Descriptive statistics were used to describe patient characteristics. MEASUREMENTS AND MAIN RESULTS: Over 12 years, 5,807 patients with 11,377 admissions for pneumonia were tested for Legionella urinary antigen. A positive Legionella urinary antigen was found in 17 patients. Cumulative incidence during the study period was 0.23%. Among the Legionella-positive patients, intensive care unit admission and median length of stay were 58.8% and 8.5 days, respectively. Most patients (64.7%) met American Thoracic Society criteria for severe pneumonia. All patients empirically received either a macrolide or fluoroquinolone covering Legionella. There were two in-hospital and three total 90-day deaths in those with a positive urinary antigen. The estimated cost of screening this population with Legionella urinary antigen was $214,438 over 13 years. CONCLUSIONS: This study reveals the low incidence of Legionella pneumonia in central Texas. Use of guideline-concordant antibiotic treatment provides coverage for Legionella. We speculate that testing in a low-prevalence area would not influence outcomes or be cost effective.

Epidemiology and clinical management of Legionnaires' disease.

Legionnaires' disease is an important cause of community-acquired and hospital-acquired pneumonia. Although uncommon, Legionnaires' disease continues to cause disease outbreaks of public health significance. The disease is caused by any species of the Gram-negative aerobic bacteria belonging to the genus Legionella; Legionella pneumophila serogroup 1 is the causative agent of most cases in Europe. In this Review we outline the global epidemiology of Legionnaires' disease, summarise its diagnosis and management, and identify research gaps and priorities. Early clinical diagnosis and prompt initiation of appropriate antibiotics for Legionella spp in all patients with community-acquired or hospital-acquired pneumonias is a crucial measure for management of the disease. Progress in typing and sequencing technologies might additionally contribute to understanding the distribution and natural history of Legionnaires' disease, and inform outbreak investigations. Control of Legionnaires' disease outbreaks relies on rapid ascertainment of descriptive epidemiological data, combined with microbiological information to identify the source and implement control measures. Further research is required to define the actual burden of disease, factors that influence susceptibility, key sources of infection, and differences in virulence between strains of Legionella species. Other requirements are improved, specific, sensitive, and rapid diagnostic tests to accurately inform management of Legionnaires' disease, and controlled clinical trials to ascertain the optimum antibiotics for treatment.

Sequence-based typing of Legionella pneumophila strains isolated from hospital water distribution systems as a complementary element of risk assessment of legionellosis in Poland.

Many factors affect the risk of Legionella infection, such as the design, construction and maintenance of water distribution systems, the presence of individuals who may be exposed and their vulnerability to infection, and the degree of water system colonization and properties of Legionella strains. For epidemiological investigations, two properties of the Legionella strains are usually determined: serotyping and genotyping (sequence-based typing, SBT). In Poland, data regarding legionellosis are fragmentary, despite the fact that this has been a notifiable disease since 2002. The number of reported cases is very low; moreover, the main method of diagnosis is serological examination (delayed diagnosis and cheaper methods), and only single cases of LD were confirmed by culture of bacteria. Therefore, after 10 years of mandatory reporting of the Legionella spp. infection in Poland, the real epidemiological situation is still unknown; however, risk assessment should be carried out, especially in hospitals. In the presented study, comparison of the sequence types of 111 isolated L. pneumophila strains (from hospital water systems) with those present in the EWGLI SBT data was undertaken for complex risk analysis as a complementary element. In total, strains of L. pneumophila belonging to 12 out of 19 STs determined in the presented study were previously reported to the EWGLI SBT database (ST1, ST42, ST59, ST81, ST87, ST114, ST152, ST191, ST371, ST421, ST461, ST520). Among these strains, only 7 STs were previously reported in the amount of ≥10 (mainly ST1, ST42, ST81). Analysis of EWGLI data were carried out and, proportionally, the highest percentage of hospital-acquired strains (clinical and environmental) was found for ST 81, ST421 and ST152, but the largest number was for ST1. Based on the EWGLI data and the presented results, it was found that persistent colonization of HWS of 3 hospitals by strains belonging to ST42, ST1, ST87 indicated an increased risk of legionellosis, especially ST42.

Quantitative risk estimation for a Legionella pneumophila infection due to whirlpool use.

Quantitative microbiological risk assessment was used to quantify the risk associated with the exposure to Legionella pneumophila in a whirlpool. Conceptually, air bubbles ascend to the surface, intercepting Legionella from the traversed water. At the surface the bubble bursts into dominantly noninhalable jet drops and inhalable film drops. Assuming that film drops carry half of the intercepted Legionella, a total of four (95% interval: 1-9) and 4.5×10(4) (4.4×10(4) - 4.7×10(4) ) cfu/min were estimated to be aerosolized for concentrations of 1 and 1,000 legionellas per liter, respectively. Using a dose-response model for guinea pigs to represent humans, infection risks for active whirlpool use with 100 cfu/L water for 15 minutes were 0.29 (∼0.11-0.48) for susceptible males and 0.22 (∼0.06-0.42) for susceptible females. A L. pneumophila concentration of ≥1,000 cfu/L water was estimated to nearly always cause an infection (mean: 0.95; 95% interval: 0.9-∼1). Estimated infection risks were time-dependent, ranging from 0.02 (0-0.11) for 1-minute exposures to 0.93 (0.86-0.97) for 2-hour exposures when the L. pneumophila concentration was 100 cfu/L water. Pool water in Dutch bathing establishments should contain <100 cfu Legionella/L water. This study suggests that stricter provisions might be required to assure adequate public health protection.

Epidemiological investigation of a Legionnaires' disease outbreak in Christchurch, New Zealand: the value of spatial methods for practical public health.

Between April and August 2005 Christchurch, New Zealand experienced an outbreak of Legionnaires' disease. There were 19 laboratory-confirmed case including three deaths. Legionella pneumophila serogroup 1 (Lpsg1) was identified as the causative agent for all cases. A case-control study indicated a geographical association between the cases but no specific common exposures. Rapid spatial epidemiological investigation confirmed the association and identified seven spatially significant case clusters. The clusters were all sourced in the same area and exhibited a clear anisotropic process (noticeable direction) revealing a plume effect consistent with aerosol dispersion from a prevailing southwesterly wind. Four out of five cases tested had indistinguishable allele profiles that also matched environmental isolates from a water cooling tower within the centre of the clusters. This tower was considered the most probable source for these clusters. The conclusion would suggest a maximum dispersal distance in this outbreak of 11·6 km. This work illustrated the value of geostatistical techniques for infectious disease epidemiology and for providing timely information during outbreak investigations.

Legionnaires' disease--risk management.

Steve Mount, an independent Legionella management consultant and trainer with over 25 years' previous experience in microbiology and UKAS-accredited Legionella analysis, underlines the rising number of nosocomial cases of Legionnaires' disease in recent years, and explains the key risk assessment, management, and monitoring steps that must be taken by those responsible for hospital water systems to comply with legislation governing the 'control and management' of Legionella risk.

Assessing risk of health care-acquired Legionnaires' disease from environmental sampling: the limits of using a strict percent positivity approach.

BACKGROUND: Elevated percent positivity (≥30%) of Legionella in hospital domestic water systems has been suggested as a metric for assessing the risk of health care-acquired Legionnaires' disease (LD). METHODS: We examined the validity of this metric by analyzing data from peer-reviewed studies containing reports of Legionella prevalence in hospital water (ie, percent positivity) and temporally matched reports of patients with health care-acquired LD. RESULTS: Our literature review identified 31 peer-reviewed publications reporting matched data. We abstracted a total of 206 data points, representing 119 hospitals, from these articles. We determined that the proposed 30% positivity metric has 59% sensitivity and 74% specificity (ie, a 41% false-negative rate and a 26% false-positive rate). These notable error rates could have significant implications, given that we identified 16 peer-reviewed articles and 6 government guidance documents that referenced the 30% positivity metric as a risk assessment tool. CONCLUSIONS: Environmental sampling of hospital water distribution systems for Legionella can be an important component of risk management for LD. However, the possible consequence of using a percent positivity metric with low sensitivity and specificity is that many hospitals might fail to mitigate when a true risk is present, or might unnecessarily allocate limited resources to deal with a negligible risk.

Clinical features and the role of atypical pathogens in nursing and healthcare-associated pneumonia (NHCAP): differences between a teaching university hospital and a community hospital.

OBJECTIVE: The Japan Respiratory Society documented a new category of guidelines for nursing and healthcare-associated pneumonia (NHCAP), which is distinct from community acquired pneumonia (CAP). The objective of this study was to determine the epidemiological differences between NHCAP patients in a teaching university hospital and a community hospital. In addition, to clarify the strategy for treatment of NHCAP, we investigated the role of atypical pathogens. METHODS: We analyzed 250 NHCAP and 421 CAP cases in a university hospital and 349 NHCAP and 374 CAP cases in a community hospital. RESULTS: Patient age and the incidences of poor general condition were significantly higher in the community hospital compared with those in the university hospital. The distribution and frequency of pathogens, especially multidrug-resistant (MDR) pathogens, were significantly different between the two hospitals. Central nervous system disorders, dementia and poor performance status, which was possibility related to aspiration pneumonia, were significantly more frequent in patients with NHCAP compared with those with CAP in both hospitals. Atypical pathogens were detected in a few cases in patients with NHCAP. CONCLUSION: There were many differences in the clinical characteristics between NHCAP patients in a university hospital and a community hospital even for hospitals located in the same area. Aspiration pneumonia was thought to be the main characteristic of NHCAP in both hospitals. Thus, all NHCAP patients did not need the same empiric therapy with a multidrug regimen directed against MDR pathogens. In addition, physicians rarely need to consider atypical pathogens in NHCAP treatment.