Legionella pneumophila infection in the Taiwan area

The aim of this study was to explore the epidemiological distribution of legionellosis among pneumonia patients in Taiwan. From January 2001 to December 2003, specimens (i.e., sputum, urine, and serum) from a total of 5097 patients with pneumonia or pneumonia-like disease registered at hospitals in the Taiwan area were analyzed for possible Legionella infection. Following the guideline issued by the Centers for Disease Control and Prevention (CDC) in the United States, a total of 237 pneumonia patients were diagnosed with legionellosis, with an incidence rate among pneumonia patients in this area of 4.7% (237/5097). The paired-serum antibody test was found to be the most effective detection method, followed by urine-antigen detection and the sputum culture method. Analysis of distribution showed that: (1) male and female occurrence rates were 70.9% (168/237) and 29.1% (69/237), respectively; (2) occurrence rates in different age groups, i.e., those aged between 61 and 80 years, those aged between 41 and 60, and those aged between 21 and 40 were 50.2% (119/237), 26.2% (62/237), and 12.2% (29/237), respectively; (3) autumn was the peak season for infection, followed by winter, summer, and spring, sequentially. This is the first study in Taiwan to have followed the three-method guideline issued by the CDC and it is the second report in Taiwan involving the investigation of a large series of pneumonia patients for legionellosis detection.