Epidemiology and Infection

Respiratory infections

Eight years of Legionnaires' disease transmission in travellers to a condominium complex in Las Vegas, Nevada

B. J. SILKa1a2 c1, M. R. MOOREa1, M. BERGTHOLDTa3, R. J. GORWITZa1a2, N. A. KOZAKa1, M. M. THAa3, E. W. BROWNa1, J. L. WINCHESTERa3, B. J. LABUSa3, P. ROWLEYa3, J. P. MIDDAUGHa3, B. S. FIELDSa1 and L. A. HICKSa1

a1 Respiratory Diseases Branch, Division of Bacterial Diseases, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, GA, USA

a2 Epidemic Intelligence Service, Office of Workforce and Career Development, Centers for Disease Control and Prevention, Atlanta, GA, USA

a3 Southern Nevada Health District, Las Vegas, NV, USA


Travel is a risk factor for Legionnaires' disease. In 2008, two cases were reported in condominium guests where we investigated a 2001 outbreak. We reinvestigated to identify additional cases and determine whether ongoing transmission resulted from persistent colonization of potable water. Exposures were assessed by matched case-control analyses (2001) and case-series interviews (2008). We sampled potable water and other water sources. Isolates were compared using sequence-based typing. From 2001 to 2008, 35 cases were identified. Confirmed cases reported after the cluster in 2001–2002 were initially considered sporadic, but retrospective case-finding identified five additional cases. Cases were more likely than controls to stay in tower 2 of the condominium [matched odds ratio (mOR) 6·1, 95% confidence interval (CI) 1·6–22·9]; transmission was associated with showering duration (mOR 23·0, 95% CI 1·4–384). We characterized a clinical isolate as sequence type 35 (ST35) and detected ST35 in samples of tower 2's potable water in 2001, 2002, and 2008. This prolonged outbreak illustrates the importance of striving for permanent Legionella eradication from potable water.

(Accepted November 30 2011)

(Online publication January 04 2012)


c1 Author for correspondence: B. J. Silk, PhD, MPH, Centers for Disease Control and Prevention, 1600 Clifton Road NE, MS C-09, Atlanta, GA 30333, USA. (Email: bsilk@cdc.gov)


Select findings from this report were presented at the Interscience Conference on Antimicrobial Agents and Chemotherapy in 2002 (San Diego, CA), the Epidemic Intelligence Service Annual Conferences in 2002 and 2010 (Atlanta, GA), and the American Public Health Association Annual Meeting in 2009 (Philadelphia, PA).