Foresight 2035: a perspective on the next decade of research on the management of Legionella spp. in engineered aquatic environments

Abstract

The disease burden from Legionella spp. infections has been increasing in many industrialized countries and, despite decades of scientific advances, ranks amongst the highest for waterborne diseases. We review here several key research areas from a multidisciplinary perspective and list critical research needs to address some of the challenges of Legionella spp. management in engineered environments. These include: (i) a consideration of Legionella species diversity and cooccurrence, beyond Legionella pneumophila only; (ii) an assessment of their environmental prevalence and clinical relevance, and how that may affect legislation, management, and intervention prioritization; (iii) a consideration of Legionella spp. sources, their definition and prioritization; (iv) the factors affecting Legionnaires' disease seasonality, how they link to sources, Legionella spp. proliferation and ecology, and how these may be affected by climate change; (v) the challenge of saving energy in buildings while controlling Legionella spp. with high water temperatures and chemical disinfection; and (vi) the ecological interactions of Legionella spp. with other microbes, and their potential as a biological control strategy. Ultimately, we call for increased interdisciplinary collaboration between multiple research domains, as well as transdisciplinary engagement and collaboration across government, industry, and science as the way toward controlling and reducing Legionella-derived infections.

Keywords: Legionella; Legionnaires’ disease; building plumbing; legionellosis; opportunistic pathogens; waterborne disease.

Figure 1.

Reported Legionnaires’ disease cases during the last two decades in Switzerland, the Netherlands, the USA, and Canada. Data obtained from www.bag.admin.ch, www.ecdc.europa.eu/en, www.cdc.gov, www.diseases.canada.ca.

Figure 2.

Examples of common sources of Legionella spp. in natural and engineered environments. Image: Rafael Pla Delgado.

Figure 3.

Example of seasonality in Legionnaires’ disease cases in New York State (2019–2023), with often 3–5 times more cases in summer than in winter. Data: New York State Department of Health. Month 1–12 is January–December, with 6–9 depicting the Northern Hemisphere summer months.

Figure 4.

Temperature fluctuations in the potable water supply of a building and the impacts thereof on Legionella spp. growth, survival, and death. The temperature responses of Legionella spp. are generalized; species-specific differences can occur. Image: Rafael Pla Delgado.

Figure 5.

Possible interactions between Legionella spp. and other prokaryotic and eukaryotic members of the microbial communities in the polymicrobial biofilms of natural and engineered aquatic environments.