Keywords
disease reservoirs
infectious disease transmission
risk factors
How to Cite
Abstract
Objective: To summarize the major findings obtained in different studies focusing on the origin of sporadic legionellosis.
Methods: A literature search was conducted in national and international journals (1990-June 2012), and those articles that fell within the scope of the study were selected. The articles have been classified into three groups: (i) studies designed to identify environmental risk factors, (ii) studies based on the transmission hypothesis from specific sources, and (iii) studies based on the spatial-temporal pattern of legionellosis.
Results: Of the 27 articles selected, half (13) were conducted in the UK or the USA and 2 in Spain. Having a travel history during the incubation period and being a professional driver were the two most frequently identified environmental risk factors. Sources of infection historically related with outbreaks, such as cooling towers and drinking water systems, have also been associated with sporadic cases. The influence of meteorological factors on incidence of the disease has been indicated in a consistent way by various authors, while studies based on spatial analysis methods are gaining in importance.
Conclusions: Despite the different hypotheses proposed about the origin of sporadic legionellosis, there is no clear epidemiological evidence regarding the sources of infection. This calls into question if the current monitoring and surveillance measures are sufficiently effective to prevent the occurrence of sporadic cases, and also highlights the need for further research.
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