Major outbreaks of Legionnaires’ disease have occurred since 1999, 31 years after the first
recorded major outbreak in 1976, in Philadelphia, PA. This has occurred, in spite of the
accumulation of a large body of knowledge about Legionella, and a plethora of government
regulations and guidelines designed to reduce transmission of the disease. The paper will
examine the causes of, and responses to, some of the major outbreaks of the last seven
years. Lessons learned from this study could prove helpful in minimizing the number and
severity of future outbreaks.