An outbreak of Legionnaires' disease linked to a municipal and industrial wastewater treatment plant, The Netherlands, September-October 2022.

Wastewater treatment plants (WWTPs) are increasingly identified as Legionnaires' disease (LD) sources. An outbreak investigation was initiated following five LD cases reported in September 2022 in Houten, the Netherlands. Case identification was based on the European LD case definition, with symptom onset from 1 September 2022, residence in or within 5 km of Houten, or visit to Houten within the incubation period, without other likely sources. We sampled potential sources and genotyped environmental and clinical isolates. We identified 15 LD cases with onset between 13 September and 23 October 2022. A spatial source identification and wind direction model suggested an industrial (iWWTP) and a municipal WWTP (mWWTP) as potential sources, with the first discharging water into the latter. Both tested positive for Legionella pneumophila serogroups 1 and 6 with multiple sequence types (ST). We detected L. pneumophila sg1 ST42 in the mWWTP, matching with one of three available clinical isolates. Following control measures at the WWTPs, no further cases were observed. This outbreak underlines that municipal and industrial WWTPs can play an important role in community LD cases and outbreaks, especially those with favourable conditions for Legionella growth and dissemination, or even non-favourable conditions for growth but with the influx of contaminated water.

Legionella detection in wastewater treatment plants with increased risk for Legionella growth and emission.

Legionnaires' disease (LD) is a severe pneumonia mainly caused by the bacterium Legionella pneumophila. Although many environmental sources of LD have been described, the sources of the majority of non-outbreak LD cases have not been identified. In several outbreaks in the Netherlands, wastewater treatment plants (WWTPs) were identified as the most likely source of infection. In this study, four criteria for Legionella growth and emission to air and surface waters were selected based on the literature and a risk matrix was drafted. An inventory was made of all WWTPs and their characteristics in the Netherlands. The risk matrix was applied to identify WWTPs at risk for Legionella growth and emission. Wastewater was collected at WWTPs with moderate to high risk for Legionella growth and emission. In 18% of the sampled WWTPs, Legionella spp. was detected using culture methods. The presented risk matrix can be used to assess the risks of Legionella growth and emission for WWTPs and support surveillance by prioritizing WWTPs. When Legionella is detected in the wastewater, it is recommended to take action to prevent emission to air or discharge on surface waters and, if possible, reduce the Legionella concentration.

Two Community Clusters of Legionnaires' Disease Directly Linked to a Biologic Wastewater Treatment Plant, the Netherlands.

A biologic wastewater treatment plant was identified as a common source for 2 consecutive Legionnaires' disease clusters in the Netherlands in 2016 and 2017. Sequence typing and transmission modeling indicated direct and long-distance transmission of Legionella, indicating this source type should also be investigated in sporadic Legionnaires' disease cases.

Increase in Legionnaires' disease cases associated with travel to Dubai among travellers from the United Kingdom, Sweden and the Netherlands, October 2016 to end August 2017.

Between 1 October 2016 and 31 August 2017, 51 Legionnaires' disease (LD) cases from the United Kingdom, Sweden and the Netherlands were identified with associated travel to Dubai. Cases did not all stay in the same accommodation, indicating that no single accommodation could be the source for all these infections. While local investigations continue into other potential sources, clinicians should remain alert to the possibility of LD among travellers returning from Dubai with respiratory illness.

[Prevention of Legionella pneumonia in the Netherlands: results from the Legionella Source Identification Unit, 2002-2012]. / Preventie van Legionella-pneumonie in Nederland: resultaten van de Bronopsporings Eenheid Legionella-pneumonie in 2002-2012.

OBJECTIVE: To study the effectiveness of a Legionella pneumonia (LP) prevention programme. DESIGN: Observational study. METHOD: We evaluated the effectiveness of the current LP prevention programme using two outcome measures, genotype match and cluster, for the period 2002-2012. If patients were associated with a source of infection via a matching or as part of a cluster it could be assumed that prevention of LP was achieved by implementing control measures for this source. By comparing genotypes we were given an indirect impression of the validity of the sampling process. RESULTS: Legionella pneumophila serogroup 1 was detected in 97 (7%) of the 1484 sampled sources. A likely source of infection was identified for 41 (2%) of the 1991 LP patients, and confirmed by matching. In more than half of these patients, the source was either a residential house or a hospital. Of the 1991 LP patients, 266 (13%) were part of a cluster. Two L. pneumophila serogroup 1 genotypes, ST47 and ST62, were present in 48% of the LP patients, but these genotypes were seldom detected in source sampling (0.9%). CONCLUSION: The current method of source detection does not adequately contribute to the prevention of LP, because the presence of L. pneumophila serogroup 1 is not often detected in the source. Other sources than those currently known are probably involved in the transmission of these bacteria. Serial infection via a common source is a substantial cause of LP, which emphasises the importance of cluster registration. It is important to identify as yet unknown alternative infection sources.

Legionnaires' disease after a campervan holiday: a case report.

This case report describes a case of Legionnaires' disease for whom the source of infection was the campervan in which the patient had travelled for 3 months. This case shows that Legionnaires' disease can be acquired by exposure to a relatively new (not previously reported) source that is commonly used as (holiday)transportation vehicle.

Results from the National Legionella Outbreak Detection Program, the Netherlands, 2002-2012.

In 2002, the National Legionella Outbreak Detection Program was implemented in the Netherlands to detect and eliminate potential sources of organisms that cause Legionnaires' disease (LD). During 2002-2012, a total of 1,991 patients with LD were reported, and 1,484 source investigations were performed. Of those sources investigated, 24.7% were positive for Legionella spp. For 266 patients with LD, 105 cluster locations were identified. A genotype match was made between a strain detected in 41 patients and a strain from a source location. Despite the systematic approach used by the program, most sources of LD infections during 2002-2012 remained undiscovered. Explorative studies are needed to identify yet undiscovered reservoirs and transmission routes for Legionella bacteria, and improved laboratory techniques are needed to detect Legionella spp. in clinical samples with a high background of microbial flora (such as soil).

Confirmed and Potential Sources of Legionella Reviewed.

Legionella bacteria are ubiquitous in natural matrices and man-made systems. However, it is not always clear if these reservoirs can act as source of infection resulting in cases of Legionnaires' disease. This review provides an overview of reservoirs of Legionella reported in the literature, other than drinking water distribution systems. Levels of evidence were developed to discriminate between potential and confirmed sources of Legionella. A total of 17 systems and matrices could be classified as confirmed sources of Legionella. Many other man-made systems or natural matrices were not classified as a confirmed source, since either no patients were linked to these reservoirs or the supporting evidence was weak. However, these systems or matrices could play an important role in the transmission of infectious Legionella bacteria; they might not yet be considered in source investigations, resulting in an underestimation of their importance. To optimize source investigations it is important to have knowledge about all the (potential) sources of Legionella. Further research is needed to unravel what the contribution is of each confirmed source, and possibly also potential sources, to the LD disease burden.

Legionnaires' disease after using an industrial pressure test pump: a case report.

INTRODUCTION: Legionnaires' disease is an acute pneumonia caused by inhalation or aspiration of aerosols contaminated with Legionella bacteria. The majority (>90%) of Legionnaires' disease cases are caused by the species Legionella pneumophila, and about 85% more specifically by L. pneumophila serogroup 1 that can be detected by a fast and easy to perform urinary antigen test. Previously reported sources of infection include cooling towers, plumbing systems of hospitals, and whirlpool spas, but for the majority of cases of Legionnaires' disease the source of infection remains unknown. CASE PRESENTATION: A 52-year-old Caucasian man was admitted to a Dutch hospital with pneumonia, where a culture of the available bronchial lavage was found positive for L. pneumophila serogroup 3, confirming the diagnosis of Legionnaires' disease. An environmental investigation identified a manually operated pressure test pump at the metal processing company where he worked as the source of infection: the water sample from the pump contained 9·8×103 colony forming units/L L. pneumophila, and sequence-based typing showed the same sequence type (ST93) for both the clinical and environmental strains. CONCLUSION: This case shows that Legionnaires' disease can be acquired by exposure to relatively rare sources that are not considered in regular control and prevention measures.