Is Legionellosis on the Rise?

Legionellosis, the oldest of the “new and emerging” infections of the past few decades, has been a clinical presence for more than 30 years. Diagnosis — initially tricky because the organism is hard to grow in culture — became easier in the 1990s with the advent of accurate urinary antigen testing.

The incidence of legionellosis (calculated from voluntary nationwide reporting to the CDC) remained steady at about 1250 cases annually for 1990–2002, then, suddenly soared to more than 2000 cases annually for 2003–2005. The surge reflected higher incidences in the Northeast and South and a disproportionate increase among middle-aged people (age range, 45–64). Rates in men exceeded those in women in all age groups both before and after this surge,…