Legionella is increasing: the silent threat in our water

In recent years we have seen a worrying trend in the Netherlands: the number of patients who become seriously ill due to Legionella is increasing rapidly. Last year, more than nine hundred people were admitted to hospital with serious pneumonia, probably with dozens of fatal consequences.

Over the past decade, the number of people hospitalized due to Legionella bacteria has more than tripled. The exact cause of this increase remains a mystery to the RIVM, because it is often a challenge to determine the source of the contamination.

We know that in the past several people have been infected through wastewater treatment plants, hot tubs or wet cooling towers. “We have indications that the majority of people become ill because the Legionella bacteria are present in the environment,” says Alvin Bartels, infection prevention policy advisor at RIVM.

Interestingly, we see a spike in cases after a prolonged warm spell followed by rainfall. Last year, many patients with serious pneumonia were also admitted to hospitals, especially during the summer months. It is estimated that about 5 to 10 percent of hospitalized patients eventually succumb to the infection, meaning that dozens of people died from Legionella in 2023 alone.

However, the real danger lies not only in the acute phase of the disease; Patients may suffer from long-lasting symptoms after infection. That is why the Legionnaires' Disease Foundation warns about the dangers of polluted water. “Water can indeed make you very ill,” says vice-chairman Diana Snijder. This patient organization is observing individuals who develop similar long-term symptoms as post-COVID. "These people experience persistent fatigue and concentration problems. I know people who have not fully recovered even after five years."

Yet even the reported cases likely represent only the tip of the iceberg. “These are only the patients who have been admitted to hospitals and tested. But many people may not even know that they have a Legionella infection,” Snijder explains. This is partly because not everyone becomes seriously ill and an infection can also cause mild symptoms.

To better monitor the bacteria, Legionnaires' Disease advocates more testing by general practitioners. “During the COVID-19 pandemic, we were all encouraged to get tested. This disease resembles COVID-19, but almost no one is tested,” says Snijder. The RIVM confirms that people aged 40 and over are increasingly at risk of serious illness as a result of Legionella.

Although preventing Legionella infection is challenging, some precautions can be taken. “Avoid misting and do not leave bags of garden soil in the sun,” Snijder advises. Bartels adds: “If you have a hot tub in your garden, it is wise to clean it regularly. You cannot prevent it completely, but fortunately the chance of you becoming ill is still relatively small.”

It has been 25 years since a major outbreak occurred in Bovenkarspel, in which 32 people died from Legionella in a short time. This reminder underlines the urgency of understanding and addressing this potentially deadly bacterium.

Legionella poses a serious threat to public health and it is critical to raise awareness and take action to mitigate and reduce this threat. Water is essential for life, but in some cases it can have a devastating effect on our health.