Determination of Legionella spp. prevalence in Spanish hotels in five years. Are tourists really at risk?

Legionella spp. is the etiological agent of the serious respiratory pneumonia known as Legionnaires' disease. This respiratory illness is frequently associated with travel and tourist resorts. Spain is an important tourist destination, and one of the top European countries concerning Legionnaires' disease cases, both community and travel associated. Still, the colonization of Legionella in our hotels remains scarce. Here, we surveyed 204 hotels in the Canary Islands, Spain, for five years (2015-2019), to determine the Legionella prevalence. Samples were obtained and analysed following national and international guidelines. We detected the pathogen in 140 of 2,318 samples (6.0%). The water distribution systems (WDS) were more colonized (7.4%) than the whirlpools (4.7%). Contamination levels were minimal (<3 log CFU L-1 ) in most of the cases, and only 3.6% of samples were highly contaminated minimal (>4 log CFU L-1 ). We isolated Legionella in 4.3% and 8.5% of cold and hot water distribution systems, respectively. The Legionella prevalence in cold water systems samples was higher when free chlorine levels were below 0.2 mg L-1 , whereas in the hot water systems samples, the prevalence was higher at <50 °C. Legionella pneumophila was the most frequently isolated species, being the members of the serogroups 2-14 the most prevalent. The annual distribution showed a colonization pick in June, followed by the winter months. Regarding the geographical distribution, the presence of Legionella was more prevalent in the western islands. Our study concludes that Legionella contamination rates in samples from facilities of the Canary Islands is lower than most of the observed in other European studies. However, corrective measures are still needed to improve Legionella control.