Expert: Portugal’s new anti-Legionella regime fits with EU tap water rules

A cooling water system in hospital. Cultures of Legionella bacteria can proliferate in warmer parts of water systems and cooling towers and then spread through the mist emitted by air-conditioning units in large buildings. [SHUTTERSTOCK]

The new Portuguese framework for the prevention and control of Legionnaires’ diseases is compatible with the flexibility allowed under the European Union’s overhauled tap water rules, a Portuguese health expert has told

Ricardo Santos, head of the water microbiology laboratory at Lisbon University’s Instituto Superior Técnico praised the EU’s revision of the Drinking Water Directive (DWD) that updates parameters of water quality set more than 20 years ago.

“It is important that the new directive starts to take into account other pathogenic organisms as, up to now, the only microbial indicator in tap water is for E. coli,” he said.

Among the updated parameters, European lawmakers decided to extend Legionella bacteria monitoring to every potable water system in the EU as part of a new risk assessment analysis.

In August, the Portuguese parliament passed a law dealing specifically with the prevention and control of the notorious bacterium.

According to Santos, this new regime of Portugal’s is quite flexible, allowing different methods and considering different layers of risk, as it puts a bigger emphasis on Legionella pneumophila, which can cause a deadly form of pneumonia.

While the new national framework on Legionnaires’ diseases falls within the competence of the health ministry, the implementation of the DWD in the Portuguese legislation will be the responsibility of different governmental agencies linked to the environmental ministry.

However, the health expert does not see room for overlapping. “I think there are good interactions between different agencies and the DWD will be aligned with the new decree,” he said.

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High-risk setting

One of the main features of the new Portuguese framework is the introduction of two different risk levels, which was considered unique by the national health department.

“Until now, there was no specific guidance on Legionella testing in different buildings like it happens for air quality,” he said.

Cultures of Legionella bacteria can proliferate in warmer parts of water systems and cooling towers and then spread through the mist emitted by air-conditioning units in large buildings.

The Portuguese legislation introduces a reinforced level of risk for cooling towers serving building with a high-risk population, like hospitals and nursing homes.

“If the sample comes from a hospital, the risk degree to take action is lower than if it comes from other buildings,” Santos said.

According to Santos, it’s a good improvement that the risk analysis operation takes into account the population served by the water system, as the risk is higher when the population is already vulnerable.

Adults over the age of 50 and people with weak immune systems, chronic lung disease or heavy tobacco users are the ones most at risk of contracting the deadly form of Legionnaires’ disease.

A Legionella ‘onion’

The new Portuguese framework also addressed the issue of detecting bacterial cultures of Legionella, which was one of the main bone of contention during negotiations at the EU level.

There are more than 60 known Legionella species; however, according to leading health bodies roughly 96% of Legionnaires’ disease is caused by just one specific species, Legionella pneumophila, which is also responsible for the deadly form of pneumonia.

According to the scientific world, the inclusion of testing for all Legionella species in the DWD might lead to a large amount of work, time, and financial expense for many end-users, and delay test results with immediate consequences for public health.

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

Likewise, in the new Portuguese system, any method to detect Legionella is allowed, as long as it is credited by the Portuguese accreditation agency. But Santos says the new framework puts a bigger emphasis on the more dangerous Legionella pneumophila.

“If we find Legionella pneumophila, the risk is always considered to be high. And you need to act accordingly,” Santos said, adding that there is no need to test for other species after that.

The solution found by the Portuguese looks like an onion, explained the health expert, as it has a first layer for Legionella pneumophila to address health problems for risk analysis and a second layer to test on species with the culture method.

“For me, it makes sense to do high-frequency testing for Legionella pneumophila and then for other species with a lower frequency, because the pneumophila is the organism that causes the huge majority of cases of the disease,” he said.

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[Edited by Josie Le Blond]


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