Prevention, monitoring favored decrease of legionellosis cases: French agency

Cases of Legionnaires’ disease reported to the French health agency Santé Publique France decreased in 2020, confirming a downward trend evident over previous years.

According to figures provided by the French public body, the number of legionellosis cases was lower than 2017, and 2019 but slightly higher than in 2016.

Legionnaires’ disease occurs by inhaling aerosols carrying Legionella bacteria which develops primarily in warm, stagnant water. The subsequent infection can then lead to a deadly form of pneumonia.

Legionella bacteria spread through vapour which can commonly come from air-conditioning units of large buildings. Adults over the age of 50 and people with weak immune systems, chronic lung disease, or heavy tobacco users are those most at risk.

The results of environmental and microbiological epidemiological investigations carried out by the agency show that water from sanitary networks remains the primary source of contamination for cases of legionellosis.

For the agency, this highlights the importance of preventative measures, monitoring, and controlling the risk of Legionella in water networks.

However, some. water networks are not subject to Legionella monitoring as it is currently compulsory only for hotels and public offices.

The current situation should be improved by implementing the recently revised EU Drinking Water Directive (DWD), which extended the monitoring of the Legionella bacteria to every potable water system in the EU as part of the new risk assessment analysis.

Despite the positive downward trend in cases, legionella remains a matter of public concern in France.

In August, a spa near the city of Meaux was closed by the local health agency after an outbreak of Legionella that led to the hospitalisation of some clients.

A deadly case of Legionnaire’s disease also occurred in the northern district of Marseille at the end of July. In June, Legionella was detected in a thermal bath in Saujon, New Aquitaine, forcing the closure of the establishment for the whole summer season.

In the same region, a high school in Jonzac was closed as Legionella bacteria colonised the showers. The 130 resident pupils were sent home until the problem was solved.

Commenting on the case on FranceInfo radio, New Aquitaine’s deputy director-general for education, Philippe Mittet said that Legionella is “a classic, well-known event which affects two or three high schools out of the 295 public high schools in New Aquitaine each year.”

All cases occured in summer when the rise in temperature makes water systems, and cooling towers warmer, creating an ideal environment for spreading bacterial cultures of Legionella, especially Legionella Pneumophila, which causes a deadly form of pneumonia.

The vast majority of detected cases – 1248 out of 1328, 94% of the total – were due to the species Legionella Pneumphila serogroup 1.

Likewise, almost all of the strains isolated were from Legionella Pneumophila – 293 from serogroup 1 and 20 from other serogroups. Four strains belonged to the species Legionella longbeachae, which grows into the soil and is not relevant for water.

Whether to assess all Legionella species or just the specific type which causes a deadly form of pneumonia, the so-called Legionella pneumophila, was a bone of contention during the negotiations on overhauling the EU’s Drinking Water Directive (DWD).

The European Commission initially proposed the inclusion of testing for both Legionella species (L.spp) and Legionella pneumophila in the DWD.

In the final compromise reached by EU lawmakers, member states were left free to determine their approach to testing. They can choose the most appropriate methods for the purposes they specify in national guidelines.

Mandatory testing in France has required the detection of Legionella pneumophila since 2001 after a major outbreak in the Georges-Pompidou hospital in Paris in 2000.

Previously, another epidemic cluster was detected in Paris in 1998, as four British citizens, supporters of the Scottish football team in the football World Cup hosted by France, developed symptoms of Legionnaires’ disease.

Since that shift toward mandatory testing given priority to Legionella pneumophila, reported outbreaks in France decreased compared to other  European countries between 2013 and 2017.

The French health agency also observed seven Legionella and SARS-CoV-2 co-infection cases among 65 patients of legionellosis reported in March 2020.

The co-infected cases were older – more often men – and presented more comorbidities with a higher case fatality.

Raised SARS-CoV-2 co-infection risk suggests other pathogens should not be overlooked

The increasing number of immunocompromised people exposed to COVID-disease combined with the raised risk of co-infections of the SARS-CoV-2 virus and respiratory pathogens creates a double whammy that cannot be overlooked.

[Edited by Alice Taylor]

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