A wake up call for continued vigilance

In the past 25 years an extensive knowledge base has been established about legionnaires' disease, and the measures needed for control and prevention from environmental sources of infection arenow legally enforced in most industrialised countries.1 Yet in spite of these advances in public health knowledge and practice, four major community outbreaks around the world have occurred in the past three years, the most recent in England.2 This outbreak and those in the Netherlands 3 and Australia4 are the largest ever in their countries, and the one in Spain last year ranks as the world's largest.5 These four outbreaks alone account for almost 1000 cases of pneumonia and around 40 deaths. They are an uncomfortable but timely reminder of how breakdowns in control or maintenance procedures can have catastrophic consequences for many people. They also raise interesting questions—namely, why were they so large in comparison with other outbreaks, why did fewer deaths occur, and …