What is legionella and what damage can it cause?

With legionella bacteria having been discovered in the water supply on the Bibby Stockholm barge just days after asylum seekers were moved onboard, we take a look at the health hazard.

What is legionella?

As Britain’s Health and Safety Executive notes, legionella bacteria occur in rivers and ponds, but only tend to cause problems in water systems where the temperature is right for them to proliferate. Such settings can include hot tubs, showers and air conditioners.

While this can occur in home settings, experts say it is more common in large buildings, for example hotels, cruise ships or hospitals.

What can it do?

If people inhale small droplets of water containing the bacteria, they can contract legionnaires’ disease, a type of severe pneumonia. While this can be treated with antibiotics, it can lead to lung failure and even death.

“Most people who get sick need care in a hospital but make a full recovery,” the US Centers for Disease Control and Prevention (CDC) states. “However, about one out of 10 people who get legionnaires’ disease will die from the infection.”

What are the symptoms of legionnaires’ disease?

According to the NHS, symptoms include a cough, shortness of breath, a high temperature, flu-like symptoms and chest pain or discomfort. People with such symptoms are advised to contact a medical professional, and tell them if they have been staying in a setting such as a hotel, spa or hospital in the past 10 days.

Legionella bacteria can also cause Pontiac fever, a mild flu-like illness. Experts say it is not clear why some people get this less severe illness while others get legionnaires’ disease when exposed to the same bacteria.

Who is most at risk?

According to the CDC, most healthy people do not get legionnaires’ disease after being exposed to legionella. But, the public health agency said: “Being 50 years or older or having certain risk factors can increase your chances of getting sick.”

Among the risk factors, are having chronic lung disease, being a smoker – or having smoked in the past – and having a weakened immune system.

What has happened to the asylum seekers on the Bibby Stockholm?

They are all being removed from the barge, although the Guardian understands no one has been identified as having contracted legionnaires’ disease.

A Dorset council spokesperson said: “No individuals have presented symptoms of legionnaires’ disease and there is no health risk to the wider community of Portland.”