Dispersion of Legionella bacteria in atmosphere: A practical source location estimation method

Abstract

Legionnaires’ disease, a form of pneumonia which can be fatal, is transmitted via the inhalation of water droplets containing Legionella bacteria. These droplets can be dispersed in the atmosphere several kilometers from their source. The most common such sources are contaminated water within cooling towers and other air-conditioning systems but other sources such as ornamental fountains and spa pools have also caused outbreaks of the disease in the past. There is an obvious need to locate and eliminate any such sources as quickly as possible. Here a maximum likelihood model estimating the source of an outbreak from case location data has been developed and implemented. Unlike previous models, the average dose exposure sub-model is formulated using a atmospheric dispersion model. How the uncertainty in inferred parameters can be estimated is discussed. The model is applied to the 2012 Edinburgh Legionnaires’ disease outbreak.

A community outbreak of Legionnaires’ disease caused by outdoor hot tubs for private use in a hotel

“…It is unlikely that these last six cases would have approached the Hotel A, that was on the outskirts of town and away from the beach. In this sense, the pattern of distribution of cases of this outbreak is very reminiscent of patterns seen in outbreaks caused by cooling towers where bioaerosols can travel hundreds of meters from the source (Sabria et al, 2006;Ferré et al, 2009;Weiss et al, 2017;Dyke et al, 2019) rather than outbreaks caused by hot tubs where typically only users or people staying in their vicinity are affected (Benkel et al, 2000;Götz et al, 2001;Den Boer et al, 2002;Coetzee et al, 2012). This could be due to several reasons.…”

Cooling Towers Influence on an Urban Environment: A Predictive Model to Control and Prevent Legionella Risk and Legionellosis Events

“…A very useful approach recently emerged during worldwide LD outbreak investigations, is the set-up of an aerosol dispersion model capable of identifying potential sources of contamination. As shown for some epidemiological events in Italy [37][38][39][40][41], this approach allows, starting from the spatial distribution of LD cases and meteorological data of the days before the onset of disease symptoms, to spatially locate risk areas, in relation to the transport and dispersion of aerosol during the infection period [23,26,[50][51][52][53].…”