Why is Legionnaires' on the Rise in the US?

Laura Cooley, MD, MPH, medical epidemiologist, Respiratory Diseases Branch, Division of Bacterial Disease, National Center for Immunization and Respiratory Disease, Centers for Disease Control and Prevention, explains the current Legionella situation.

Interview Transcript (slightly modified for readability)

“[So far], 2016 [has been] a big year for Legionella and Legionnaires’ disease. It was 40 years ago that the first outbreak was investigated, and in the intervening years tremendous amount of progress has been made, particularly [with] understanding risk factors for legionnaires disease and the relationship of Legionella with the environment and building water-systems. But even with all this progress, the reported number of cases continues to rise; and, in fact, in 2014, there was a 286% increase when compared with the year 2000 as far as [the] reported cases of Legionnaires’ disease. There’s a lot of work yet to be done.

In 2014 there were about 5000 cases reported. We think that this is probably an underestimate. The reason for this increase for reported cases is not exactly clear, [it’s] probably multi-factorial. Some of it could have to do with better surveillance, better awareness of testing, [or] better testing mechanisms. But there is reason to believe that there is also an increase in [the] disease itself, [which] that could be due to a number of factors as well, [such as] an increase in the number of people at risk for Legionnaires’ disease, so an aging US population; more people on immunocompromising medications; also it could have to do with aging infrastructure in the United States, so older plumbing systems; and then the climate could be playing a role with warmer temperatures.”