Sydney CBD Legionnaires’ Disease Outbreak

A Sudden Health Crisis in the Heart of Sydney

In April 2025, Sydney’s busy Central Business District (CBD) became the centre of a serious public health investigation. Twelve people contracted Legionnaires’ disease after spending time in the city between March 13 and April 5. Tragically, one man in his 50s passed away, while several others were hospitalised with severe pneumonia-like symptoms.

Notably, the cases were unconnected-the individuals did not know each other-which suggested a shared environmental source rather than person-to-person spread. That’s a hallmark feature of this disease, and one that makes swift public health action absolutely crucial.

What Is Legionnaires’ Disease?

An Airborne Threat from Water Systems

Legionnaires’ disease is a serious lung infection caused by inhaling microscopic droplets of water contaminated with Legionella bacteria. These bacteria multiply in warm, stagnant water and can be dispersed into the air through systems like cooling towers, large air conditioning units, spa pools, and plumbing systems.

It cannot be spread from person to person, but once airborne, the contaminated mist can be inhaled unknowingly by anyone nearby — often in places like hotels, office buildings, shopping centres, or gyms.

Symptoms and Diagnosis

The disease typically develops within 2 to 10 days after exposure. Early symptoms resemble flu or pneumonia and may include:

• High fever and chills

• Cough and shortness of breath

• Muscle aches

• Headache

• Diarrhoea and vomiting

• Fatigue and confusion

In vulnerable individuals, complications can escalate rapidly, sometimes resulting in respiratory failure or septic shock if left untreated.

Identifying the Source of the Legionnaires Disease Outbreak in Sydney

In response to the Sydney Legionnaires Disease outbreak, NSW Health launched a full-scale investigation. Environmental health officers tested over 165 cooling towers in the CBD. Legionella bacteria were confirmed in at least one of them, which was promptly decontaminated. However, further testing was required to confirm a definitive link between the bacteria found and the patients infected.

Dr. Vicky Shepheard of the South Eastern Sydney Local Health District urged anyone who had been in the area during the affected period and was feeling unwell to seek medical care quickly. This proactive public messaging played a vital role in identifying more cases and containing the risk.

Public Health Response and Lessons

An Immediate, Coordinated Effort

Health authorities acted quickly. Cooling towers were tested, maintenance logs reviewed, and building owners were reminded of their legal responsibilities under the NSW Public Health Regulation 2022. Most owners cooperated fully, with systems disinfected where required and follow-up inspections carried out.

This outbreak was a powerful reminder that proper maintenance of water systems isn’t just a legal box to tick — it’s a public safety priority.

Could It Happen Here in the UK?

Although this particular incident happened in Australia, similar risks exist in the UK. Legionella bacteria don’t respect borders. In fact, commercial buildings across the UK - especially those with complex water systems like hospitals, care homes, schools, and office blocks - face comparable challenges.

Proper water hygiene protocols, routine maintenance, and thorough risk assessments are essential to keeping people safe and preventing outbreaks like this from happening here.

Who’s Most at Risk?

While anyone can be affected, the risk is significantly higher for:

• Adults over 50

• Smokers

• People with chronic lung conditions

• Those with weakened immune systems

Even healthy individuals can become seriously ill, particularly if the exposure dose is high or if diagnosis is delayed.

Preventing Future Outbreaks

Prevention hinges on good design, regular maintenance, and compliance with health guidance. For building managers, that means ensuring:

• Cooling towers and evaporative condensers are kept clean and tested regularly

• Water temperatures are controlled to prevent bacterial growth

• Stagnant water is eliminated from pipework

• Maintenance records are up to date and readily available

It’s not just about meeting regulations — it’s about keeping people safe.

Stay Informed, Stay Vigilant

Legionnaires’ disease is rare, but when outbreaks occur, they can be sudden and serious. The situation in Sydney is a sharp reminder that risks may be hidden in plain sight — in cooling towers above our heads or plumbing systems behind the walls.

For those responsible for maintaining commercial or public buildings, regular checks and water hygiene reviews are key. And for the public, being aware of symptoms and acting quickly can save lives.

If you’re interested in learning more about Legionella risks in the UK — including regulations, common causes, and how they’re managed — visit our Learning Centre.