Legionella belongs to Gram-negative bacilli, and more than 30 kinds of Legionella have been found, among which Legionella pneumophila is the most pathogenic. Human infection with Legionella can cause two types, one is mainly fever, symptoms similar to the flu, such as nasal congestion, runny nose and mild cough, with a certain self-limiting, so it is also called Pontiac fever. The other type causes Legionella pneumonia, which can cause severe symptoms such as general malaise, muscle pain, dry cough and fever, and will gradually worsen as the disease progresses, with symptoms such as chills, high fever, chest pain and relatively slow pulse. Wet rales can be heard on auscultation of the lungs, and solid lung shadows can be seen on chest films and CT of the lungs. If the treatment is not timely, it can cause gastrointestinal abnormalities, such as nausea, vomiting, abdominal pain and diarrhea, cause abnormal liver function, and in serious cases, shock, respiratory distress and even coma can occur, with a high mortality rate. Therefore, Legionella infection should be treated promptly, and erythromycin treatment is generally preferred and can be cured in about three weeks.