Legionnaires' Disease at a Dutch Flower Show: Prognostic Factors and Impact of Therapy

Kamilla D. Lettinga, Annelies Verbon, Gerrit-Jan Weverling, Joop F.P. Schellekens, Jeroen W. Den Boer, Ed P.F. Yzerman, Jacobus Prins, Wim G. Boersma, Ruud J. van Ketel, Jan M. Prins, Peter Speelman


Emerging Infectious Diseases. 2002;8(12) 

In This Article

Abstract and Introduction

After a large outbreak of Legionnaires' disease in the Netherlands, we determined risk factors for intensive care unit (ICU) admission and death and the impact of adequate therapy on ICU-free survival among 141 hospitalized patients. Overall mortality rate was 13%, and ICU mortality rate was 36%. Smoking, temperature >38.5°C, and bilateral infiltrates shown on chest x-ray were independent risk factors for ICU admission or death (all p<0.05). Starting adequate therapy within 24 hours after admission resulted in a higher ICU-free survival rate compared to therapy initiation after 24 hours: 78% versus 54%, respectively (p=0.005). However, delay in providing therapy to patients with urinary antigen tests with negative results did not influence outcome. These data suggest that by using the urinary antigen test on admission a more tailored approach to patients with community-acquired pneumonia may be applied.

Severe Legionnaires' disease has an overall mortality rate of 10% to 30%,[1,2,3] and 30% to 50% of patients require admission to an intensive care unit (ICU).[1,4] One of the most important determinants of outcome is the early initiation of adequate therapy after admission.[1,5] Administering appropriate antibiotics for Legionella pneumophila during the empiric treatment of patients with community acquired pneumonia has been advocated.[6] Given the low frequency of Legionnaires' disease, this strategy is costly and leads to overconsumption of antibiotics. Therefore, many physicians have not adopted these guidelines in daily practice. Identifying those patients with community-acquired pneumonia caused by L. pneumophila is difficult.

In March 1999 one of the largest outbreaks of Legionnaires' disease since the first described outbreak in Philadelphia[7] occurred in the Netherlands. The outbreak originated at the Westfriesian Flora, an annual flower show combined with a consumer products exhibition, held February 19-February 28, 1999. The flower show was visited by 77,061 persons, and Legionnaires' disease developed in at least 188.[8] The size of the outbreak provided a unique opportunity to determine which clinical factors on hospital admission predict ICU admission or death (ICU/death). We also evaluated whether the rapid urinary antigen test can help identify those patients with Legionnaires' disease for whom adequate therapy cannot be delayed.