The UK Health Security Agency (UKHSA) has shared its latest update on Legionnaires' disease. In a new message, the government agency emphasised that the lung infection is 'uncommon' but can be 'serious', particularly for some groups of people.

In the UKHSA's latest update, it said the infection can be particularly serious for older adults, smokers, or people with underlying health conditions. The post, shared on X, said: "Legionnaires' disease is a serious type of pneumonia caused by the bacterium Legionella pneumophila. People contract the disease by breathing in fine water droplets containing Legionella."

The post also shared awareness of how people contract Legionnaires' disease. UKHSA explained: "This bacteria thrives in warm, stagnant water such as hot tubs, plumbing systems, and large air-conditioning units."

The warning comes after UKHSA said it had recorded a rise in cases of Legionnaires' disease in parts of north-west and south-west London. An investigation is underway, reports the Mirror.

Dr Janice Lo, consultant in health protection for London at the UKHSA, said: "At this stage, a common source has not yet been confirmed, but we are undertaking further investigations, with partners, that will provide us with more information.

"Legionella bacteria is widely distributed in the environment and can multiply in large water systems within buildings. It is important that water systems are properly maintained with regular testing and treatment to ensure that bacteria do not multiply and cause a risk to health."

According to the NHS, people get Legionnaires' disease by breathing in water droplets containing Legionella bacteria. The health service adds that Legionnaires' disease is usually caught in places like offices, hospitals, or hotels when bacteria get into the water supply. You can get Legionnaires' disease from air conditioning systems, spa pools and hot tubs, taps or showers that are not used often, and humidifiers.

You usually cannot get Legionnaires' disease from drinking water, other people with the infection, or places like rivers and ponds. As per the health service, symptoms of Legionnaires' disease include:

• a cough
• shortness of breath
• chest pain or discomfort, particularly when breathing or coughing
• a high temperature
• flu-like symptoms

Legionnaires' disease is usually treated in hospitals, and most people make a full recovery. You should ask for an urgent GP appointment or contact NHS 111 if you experience symptoms of Legionnaires' disease, such as:

• a cough that's lasted three weeks or more
• coughing up blood
• chest pain that comes and goes, or happens when breathing or coughing
• feeling short of breath

Tell your doctor where you have spent the last ten days, for instance, if you stayed in a hospital, spa or hotel. As per the NHS, treatment may include antibiotics given directly into a vein, oxygen through a face mask or tubes in your nose, and a machine to help you breathe.

Antibiotic treatment usually lasts between one and three weeks. The UKHSA's primary responsibility is to protect the public's health in England.