An outbreak of Legionnaires' disease associated with a circulating bathwater system at a public bathhouse. II: radiological findings of pneumonia.

In July 2002, one of the largest outbreaks of Legionnaires' disease associated with a public bathhouse in Japan occurred in Miyazaki. The local government and the University of Miyazaki performed a retrospective investigation of those persons who were considered to have been exposed to Legionella. This investigation provided a unique opportunity to analyze the clinical presentation of patients with outbreak-associated Legionnaires' disease. The purpose of the present study was to analyze high-resolution computerized tomography (HRCT) scans for the characteristic findings of Legionnaires' disease and to evaluate the correlation between the radiological severity on the initial chest X-ray and the outcome of the patients. Radiological findings of HRCT were analyzed in 35 patients. The radiological severity on chest X-ray was evaluated in 69 patients, utilizing the pneumonia scoring system proposed by the Research Committee on Legionnaires' Disease of the Ministry of Health, Labour and Welfare of the Japanese Government. Air-space consolidation, ground-glass opacity, and pleural effusion were common features on HRCT in patients with Legionnaires' disease. Typical HRCT findings showed bilateral multilobar infiltrates in the subpleural areas without centrilobular opacities. Multivariate logistic regression analysis identified male sex, short incubation period, high serum C-reactive protein, high serum alanine aminotransferase, hyponatremia, and positive Legionella urinary antigen test results as independent risk factors for high pneumonia scores. Patients with high pneumonia scores required significantly longer hospitalization and showed poor prognoses.