OUT OF THE SHADOWS
Legionella Pneumophila (Legionnaire's Disease)
Legionella arrived on the public scene with a dramatic appearance in a Philadelphia hotel the summer of 1976. The hotel was hosting the American Legion Convention, a veteran's organization that boasted more than 4,000 attendees at its gathering. More than 200 of the elderly attendees at the convention began coming down with mild coughs and low fevers.
Soon after the convention, many of the afflicted developed a rapidly progressive pneumonia, muscle aches, and an incredibly high fever spiking up to 105 degrees. Thirty-four of the attendees passed into a coma and died because of exposure to Legionella. The public's fears about the unknown, deadly pathogen weren't answered until the following year. In 1977, the bacterium Legionella pneumophila was identified by the Centers for Disease Control and Prevention (CDC) and named after the first unfortunate victims.
Legionella pneumophila turned out to be one species in the large family of Legionella bacteria (see Figure 6-1). While, to date, all major outbreaks of Legionnaire's disease were determined as being caused by L. pneumophila, sporadic cases have been caused by the other subspecies. It was determined that although exposure to Legionella was unlikely to result in infection, the mortality rate is startlingly high. As many as one out of eight people