Legionellosis is a term used to describe infections caused by Legionella bacteria, particularly Legionella pneumophila. This bacterium is commonly found in fresh water sources such as rivers and lakes, but can also be present in man-made water systems like cooling towers, hot tubs, and plumbing systems. Legionellosis primarily includes two forms of infection: Legionnaires' disease, which is a severe form of pneumonia, and Pontiac fever, which is a milder, flu-like illness. Legionnaires' disease is characterized by symptoms such as high fever, chills, cough, and shortness of breath, and can be life-threatening, especially in individuals with weakened immune systems or underlying health conditions. Pontiac fever, on the other hand, is a self-limiting illness that typically resolves on its own without treatment. Research in the field of legionellosis focuses on understanding the epidemiology, pathogenesis, diagnosis, treatment, and prevention of infections caused by Legionella bacteria. This includes studying the various risk factors associated with Legionella exposure, developing effective diagnostic tests, exploring new treatment options, and implementing strategies to control the spread of the bacteria in water systems. By advancing our knowledge of legionellosis, researchers aim to improve the management and prevention of these potentially serious infections.