Update 2 November 2026: Fogging atmospheric fireplaces

A cluster of four patients with legionella pneumonia (pneumonia caused by the legionella bacterium) has been identified in the Netherlands. The patients have all recovered. These four patients all stayed within the same hotel, but not during the same time.

During research, a misting atmospheric fireplace (damphaard) emerged as a source in a hotel. This is a device that mimics the effect of a fireplace with atomized water and light. High concentrations of legionella bacteria have been detected in the water tank of this fireplace. Nebulizing atmospheric fireplaces can mist water at a temperature in which legionella can grow well. They occur in public spaces and in people's homes. This source of legionellosis has so far been little described.

What can you do?

For all devices that mist water (such as misting atmospheric fireplaces and humidifiers) it is important to always:

• read the manufacturer's instructions for use
• follow the instructions for use and cleaning

Update 28 July 2026

More cases of legionellosis reported in the Netherlands in 2025
 

In 2025, National Institute for Public Health and the Environment, RIVM, received more reports of legionellosis than in 2024. However, the number of reports was lower than in 2023. In that year, the number of reports was exceptionally high. Legionellosis is an infection that is caused by the Legionella bacterium. When this bacterium leads to pneumonia, it is also called ‘Legionnaires' disease’. In its recently published review of 2025, RIVM sets out the main findings.

Key results:

• In 2025, 739 cases of legionellosis were reported in the Netherlands. Legionnaires’ disease was diagnosed in 729 people.
  The disease was most common among people over the age of 50 and almost three-quarters of the patients were male.
• Almost all patients had one or more risk factors, such as advanced age, smoking or another medical condition.
  97% of patients were admitted to hospital; more than 1 in 4 needed to be admitted to an intensive care unit. 30 patients died.
• Most infections (over 70%) were contracted in the Netherlands. A smaller proportion of patients (almost 30%) probably fell ill whilst abroad.
• The number of infections contracted in the Netherlands was similar to the years 2021 and 2022. The total number of infections in 2021 and 2022 was lower than in 2025 because fewer infections were contracted abroad due to the COVID-19 pandemic.
• In 2025, several patient groups (clusters) were studied as well. No common sources were found in these clusters. However, in 2025, sources were identified for 2 patients through a genotypic match: a sauna and a hot tub.

Read the 2025 retrospective (Dutch only): Terugblik surveillance legionellose in Nederland in 2025 | RIVM.