Environmental surveillance of Legionella in tourist facilities of the Balearic Islands, Spain, 2006 to 2010 and 2015 to 2018

BACKGROUND: Legionnaires’ disease is a respiratory illness often associated with hotels and travel. Spain is a major tourist destination and one of the European countries with most cases of Legionnaires’ disease , both community- and travel-associated. However, the prevalence of Legionella in tourist facilities is unknown. AIM: The present investigation aimed to survey the tourist facilities in the Balearic Islands, Spain, for Legionella prevalence. METHODS: We visited tourist facilities in the Balearic Islands in two different periods (2006–2010 and 2015–2018) and took water samples following national and international guidelines. Legionella was investigated by culture methods following international standards (ISO 11731:1998). RESULTS: We evaluated 13,472 samples from 465 facilities. Bacteria of the Legionella genus were detected in 65.4% of the surveyed facilities. Contamination of the facilities was significantly higher during the second decade (54.5 vs 78.6%). The most frequent colonisers were L. pneumophila serogroup 2–14. We detected the pathogen in 15.9% and 6.9% of hot and cold water distribution systems samples, respectively. The Legionella contamination rate in cold water systems samples was higher when free chlorine levels were < 0.2 mg/L and at > 25 °C temperatures, while in the hot water systems samples, the contamination rate was higher at < 50 °C. Of the samples from hot tubs, 10.9% were contaminated. CONCLUSION: Legionella prevalence in hotels in the Balearic Islands was high but the contamination rates depended on the installations. Corrective measures are still needed to improve Legionella control.