Background.

Legionella species have their natural habitat or primary reservoir in the fresh surface waters of lakes, rivers, ponds and hot springs, from where they colonize drinking water through supply systems. The present study aims to investigate the prevalence of Legionella in drinking water facilities in Spain.

Methods.

A systematic review was performed by searching in electronic databases of scientific information for observational studies on contamination of drinking water by Legionella, with results of analysis of water samples obtained between January 2001 and April 2021. Meta-analysis was carried out using the MetaXL© software in the Microsoft Excel spreadsheet.

Results.

A total of 21 studies were selected. The prevalence of Legionella in Spain was 21.8 % (95 % CI: 15.0-29.6). The most commonly isolated species were L. pneumophila serogroups 2-15 (44.4 %, 95 % CI: 29.5-59.8). The highest values were found at terminal points of the sanitary hot water networks (31.7 %, 95 % CI: 21.6-42.9), and in the autonomous regions of Aragon (24.7 %, 95 % CI: 8.8-44.9) and Catalonia (21.3 %, 95 % CI: 4.4-44.8).

Conclusions.

The overall prevalence of Legionella obtained can be compared to studies performed by other authors, being in general terms close to that obtained worldwide, with variations in relation to other countries. The facilities with the highest prevalence have turned out to be those with the highest risk of proliferation and dispersal of the bacteria according to current regulations, and those located in the eastern half of Spain.