Legionella pneumonia is an inflammation of the lungs due to Legionella infection. The manifestations of CT mainly include lamellar alveolar infiltrates at typical lesions, which gradually turn into infiltrates of the lung parenchyma and become substantial pneumonia. Most are located in the lower lobes of the lung, occur bilaterally or unilaterally, develop rapidly, and may often be accompanied by pleural effusion. If the effusion is excessive, it may compress the lung tissue and cause compensatory emphysema or pulmonary atelectasis. In patients with poor resistance, there may also be cavities of different sizes and numbers in the lung, with abscess formation inside the cavity. In cases where the patient is treated with medication, such as erythromycin, the effusion and exudate will slowly decrease until it disappears.