Legionella is a genus of bacteria that includes over 60 different species, with Legionella pneumophila being the most well-known and significant for human health. This bacterium is naturally found in aquatic ecosystems, including surface and groundwater, as well as in moist soil. In these natural environments, Legionella is present in small quantities and typically does not pose a threat. However, problems arise when these bacteria proliferate in human-made water systems, such as air conditioning systems and plumbing networks, where they find ideal conditions for growth and spread. In addition to Legionella pneumophila, there is also Legionella longbeachae, which is rarer but can also cause Legionnaires' disease. This species is associated with contaminated soil and compost. Infection is transmitted through inhalation of soil-contaminated particles and is particularly hazardous for individuals involved in gardening or other activities that involve contact with materials that may harbor the bacteria.To protect public health, it is important to understand the biology of Legionella bacteria, including their virulence factors and modes of transmission. Preventive measures include regular maintenance and servicing of water systems, including cleaning and disinfection, as well as maintaining water temperatures to prevent bacterial proliferation. Additionally, awareness of risks associated with contaminated soil and taking appropriate protective measures is crucial. A combination of scientific knowledge, technical expertise, and careful oversight can significantly reduce the risk of Legionnaires' disease outbreaks and improve safety in water systems and the environment.