The study is designed to identify legionellosis, an infection caused by the pathogen Legionella pneumophila. Legionellosis (legionnaires' disease) is an infectious disease caused by legionella, special bacteria that actively multiply in air conditioning systems, inhalers, humidifiers, wherever there is a closed freshwater circulation system. Legionellosis varies in severity from a mild febrile illness to a serious and sometimes fatal form of pneumonia. Diagnosis of legionellosis consists in studying the clinical and anamnestic data, the epidemiological situation, and the results of the patient's examination. The signs of legionellosis are wheezing and bilateral crepitation. However, since such symptoms are non-specific, instrumental and laboratory diagnostics should be performed. Due to the similarity of symptoms, legionellosis is easily confused with pneumonia, Ku fever, acute respiratory viral infections and ornithosis, therefore, diagnosis should be carried out under the supervision of an infectious disease specialist. The study has a high specificity (98%) and sensitivity (95%) and makes it possible to quickly and accurately diagnose the infection.