Seasonal variation of Legionnaires' disease in Scotland

B, Raj; Fallon, R. J.

doi:10.1016/0163-4453(91)91569-j

Cited by 22 publications

(13 citation statements)

References 12 publications

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“…This rapid proliferation of L. pneumophila, in less than 3 weeks, may correspond to an increase in the "background" concentration of L. pneumophila in the environment during the summer, leading to the contamination of the system through water or air. A summer and autumn peak in incidence has been described as a characteristic epidemiological feature of Legionnaires' disease in Europe (11). Furthermore, a seasonal pattern of infection has been reported by Fliermans et al (18), who injected guinea pigs with sample water collected monthly from a thermally altered lake, the highest frequency of infection by L. pneumophila occurring during the summer months.…”

Section: Discussionmentioning

confidence: 87%

“…Such a seasonal variation may well be due to the facts that Legionella spp. multiply faster in the warmer waters of summer and that the greater use of cooling towers in summer provides opportunities for dissemination (11). During the investigation of Legionella colonization in 31 cooling towers in South Australia, it was found that between 60 and 75% of the cooling towers studied were colonized by Legionella during the summer months but only 20 to 30% were colonized during the winter (8).…”

Section: Discussionmentioning

confidence: 99%

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Dynamics of Legionella spp. and Bacterial Populations during the Proliferation of L. pneumophila in a Cooling Tower Facility

Wéry

Bru-Adan

Minervini

et al. 2008

Appl Environ Microbiol

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The dynamics of Legionella spp. and of dominant bacteria were investigated in water from a cooling tower plant over a 9-month period which included several weeks when Legionella pneumophila proliferated. The structural diversity of both the bacteria and the Legionella spp. was monitored by a fingerprint technique, single-strand conformation polymorphism, and Legionella spp. and L. pneumophila were quantified by real-time quantitative PCR. The structure of the bacterial community did not change over time, but it was perturbed periodically by chemical treatment or biofilm detachment. In contrast, the structure of the Legionella sp. population changed in different periods, its dynamics at times showing stability but also a rapid major shift during the proliferation of L. pneumophila in July. The dynamics of the Legionella spp. and of dominant bacteria were not correlated. In particular, no change in the bacterial community structure was observed during the proliferation of L. pneumophila. Legionella spp. present in the cooling tower system were identified by cloning and sequencing of 16S rRNA genes. A high diversity of Legionella spp. was observed before proliferation, including L. lytica, L. fallonii, and other Legionella-like amoebal pathogen types, along with as-yet-undescribed species. During the proliferation of L. pneumophila, Legionella sp. diversity decreased significantly, L. fallonii and L. pneumophila being the main species recovered.

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Section: Discussionmentioning

confidence: 87%

Section: Discussionmentioning

confidence: 99%

Dynamics of Legionella spp. and Bacterial Populations during the Proliferation of L. pneumophila in a Cooling Tower Facility

Wéry

Bru-Adan

Minervini

et al. 2008

Appl Environ Microbiol

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“…The Greater Toronto Area (GTA) in Canada has experienced a gradual increase in legionellosis incidence during the past two decades, although this may be attributable in part to improved recognition and diagnosis of disease (Benin et al, 2002;Joseph, 2004). However, it also is possible that the changing patterns of disease reflect changes in local environmental conditions (Fisman et al, 2005;Straus et al, 1996;Bhopal and Fallon, 1991b;Hicks et al, 2007). Improved understanding of environmental factors associated with legionellosis would aid formulation of prevention strategies and could enhance recognition of cases by clinicians.…”

Section: Introductionmentioning

confidence: 97%

Going with the Flow: Legionellosis Risk in Toronto, Canada Is Strongly Associated with Local Watershed Hydrology

Tang²,

Jamieson³

et al. 2008

EcoHealth

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Legionella species are increasingly recognized as a cause of both healthcare- and community-acquired pneumonia (so-called "Legionnaire's disease"). These pathogens are ubiquitous in the environment, but environmental factors in the occurrence of sporadic legionellosis remain poorly understood. We analyzed all legionellosis cases identified in the Greater Toronto Area of Ontario from 1978 to 2006, and evaluated seasonal and environmental patterns in legionellosis case occurrence by using both negative binomial models and case-crossover analysis. A total of 837 cases were reported during the study period. After adjusting for seasonal effects, changes in the local watershed, rather than weather, were the strongest contributors to legionellosis risk. A 3.6-fold increase (95% confidence interval (CI), 2.4-5.3) in odds of disease was identified with decreasing watershed levels approximately 4 weeks before case-occurrence. We also found a 33% increase (95% CI, 8-64%) in odds of disease with decreasing lake temperature during the same period and a 34% increase (95% CI, 14-57%) with increasing humidity 5 weeks before case-occurrence. We conclude that local watershed ecology influences the risk of legionellosis, notwithstanding the availability of advanced water treatment capacity in Toronto. Enhancement of risk might occur through direct contamination of water sources or via introduction of micronutrients or commensal organisms into residential and hospital water supplies. These observations suggest testable hypotheses for future empiric studies.

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“…Two outbreaks in Australia [1,2] occurred in late April (mid-autumn). Bhopal and Fallon [3] have reported an autumn peak in incidence of cooling tower-associated outbreaks in Scotland. Reasons for this peak are unclear, and they speculated cleaning of towers or higher legionella concentrations at the end of summer might be contributing factors.…”

Section: Introductionmentioning

confidence: 99%

A model for autumn outbreaks of Legionnaires' disease associated with cooling towers, linked to system operation and size

Bentham

Broadbent

1993

Epidemiol. Infect.

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SUMMARYCooling towers have been demonstrated to be amplifiers and disseminators of legionella, the causative organism of Legionnaires' disease. Community outbreaks associated with cooling towers have been reported with several common factors. Small towers (< 300 kW) have predominantly been implicated in outbreaks. Cooling tower-associated outbreaks are most frequent in autumn, and frequently implicated systems have been operated after a period of shutdown.This paper reports field study data relating system operation to legionella colonization of systems. Operating systems have been shown to be more frequently colonized by legionella than shutdown systems. In some cases operation of systems after periods of shutdown raised legionella concentrations from below detection limits to between 50 and 950 c.f.u./ml within 10 min.These data and previously reported data relating to biofilm and sediment colonization of the systems, and community outbreaks of Legionnaires' disease, have been used to develop a model explaining the seasonal nature of outbreaks associated with irregularly operated, small cooling tower systems.

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Seasonal variation of Legionnaires' disease in Scotland

Cited by 22 publications

References 12 publications

Dynamics of Legionella spp. and Bacterial Populations during the Proliferation of L. pneumophila in a Cooling Tower Facility

Dynamics of Legionella spp. and Bacterial Populations during the Proliferation of L. pneumophila in a Cooling Tower Facility

Going with the Flow: Legionellosis Risk in Toronto, Canada Is Strongly Associated with Local Watershed Hydrology

A model for autumn outbreaks of Legionnaires' disease associated with cooling towers, linked to system operation and size

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