Review Article
Koichi Nishimura
Abstract
According to the definition in the Air and Water borne Diseases journal home page, waterborne diseases are infectious in nature that spread primarily through contaminated water. I have been a chest physician in the Department of Respiratory Medicine for the past three decades in Japan. While we often see patients with airborne diseases in clinical practice, it is rare to examine subjects with symptoms suggesting waterborne disease. Since the first recorded outbreak of Legionella pneumophila pneumonia in Philadelphia in 1976, many outbreaks have been reported. Geographic differences in the epidemiology of Legionella infection underscore the importance of knowing local patterns. In Western countries, outbreaks often are traced to cooling towers, air-conditioners, humidifiers and respiratory-therapy equipment. Legionella pneumonia can be acquired by inhalation of aerosols containing Legionella species or by micro aspiration of water contaminated with Legionella species. Most Japanese enjoy this traditional style of communal bathing, especially at one of the many rustic hot-springs bathing (“onsen”). Until recently, clinicians never expected to see patients with Legionella pneumonia transmitted in an onsen. In this brief review; I intend to introduce the relationship between Legionella pneumonia and onsen in Japan.