A cluster of Legionnaires' disease in Belgium linked to a cooling tower, August-September 2016: practical approach and challenges.

N Hammami,T Moens,V Laisnez,D Uvijn,L Van Zandweghe,W Bultynck,E Robesyn,I Wybo,L Van De Ginste,C Broucke,A Van Damme,W Temmerman

doi:10.1017/s0950268819001821

Abstract

A cluster of Legionnaires' disease (LD) with 10 confirmed, three probable and four possible cases occurred in August and September 2016 in Dendermonde, Belgium. The incidence in the district was 7 cases/100 000 population, exceeding the maximum annual incidence in the previous 5 years of 1.5/100 000. Epidemiological, environmental and geographical investigations identified a cooling tower (CT) as the most likely source. The case risk around the tower decreased with increasing distance and was highest within 5 km. Legionella pneumophila serogroup 1, ST48, was identified in a human respiratory sample but could not be matched with the environmental results. Public health authorities imposed measures to control the contamination of the CT and organised follow-up sampling. We identified obstacles encountered during the cluster investigation and formulated recommendations for improved LD cluster management, including faster coordination of teams through the outbreak control team, improved communication about clinical and environmental sample analysis, more detailed documentation of potential exposures obtained through the case questionnaire and earlier use of a geographical information tool to compare potential sources and for hypothesis generation.

Highlights

Legionnaires’ disease (LD) is pneumonia caused by Legionella spp. and is often severe [1]
We describe a cluster of LD in Dendermonde, a district in Belgium, with a population of 198 494 [11]
Clinicians in one hospital mentioned an increase in admissions for pneumonia since 25th August. They identified – mostly retrospectively – 23 suspect patients admitted in two hospitals, with date of onset between 20th August and 12th September

Summary

Introduction

Legionnaires’ disease (LD) is pneumonia caused by Legionella spp. and is often severe [1]. Diagnosis and appropriate treatment are important to improve the clinical outcome. Infection occurs by inhalation of aerosolised contaminated water particles. Aerosol-generating devices such as cooling towers (CTs), spa-pools, showers and fountains can infect people indoor or outdoor, and can cause outbreaks [2,3,4,5,6,7]. LD is a notifiable infection in Belgium to allow for source identification and adequate control measures to prevent new infections [1, 8, 9]. In 2015, Belgium reported 165 cases of LD to the European Centre of Disease Prevention and Control (ECDC) [10], a national notification rate of 1.47/100 000

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