A second person has died from an outbreak of legionnaires’ disease in Sydney’s CBD – with three other victims admitted to hospital.

NSW Health said a dozen people who had been in and around the CBD in March and April had contracted the illness.

Legionnaires’ disease is a severe form of pneumonia caused by Legionella bacteria,

and widespread outbreaks have often been traced to the presence of that bacteria in air conditioning cooling towers.

‘Sadly, one of the people who contracted the disease passed away in hospital last week,’ a spokesperson said.

Three residents from Potts Point, aged between their 40s and 70s, not known to each other were admitted to hospital after becoming unwell.

More than 165 cooling towers across Sydney have been inspected as part of the investigation into the source of the outbreak.

NSW Health found legionella bacteria in one of the towers which is being cleaned, with more testing required to determine if it was the source of the spread.

Local businesses have been asked to disinfect their water cooling systems to kill any bacteria in cooling towers, spas, hot water tanks, and air conditioning units.

Director of the Public Health Unit at South Eastern Sydney Local Health District Dr Vicky Sheppeard said the virus could not be spread between people.

‘Outbreaks sometimes occur when bacteria from environmental sources such as cooling towers atop large buildings become contaminated,’ she said.

Symptoms include fever, cough, shortness of breath, and muscle aches, often appearing two to 10 days after exposure.

While serious, the disease is treatable with antibiotics, but can be fatal if people don’t seek medical help.

Legionnaires’ disease is more dangerous for people with compromised immune systems or underlying health conditions.

Those most at risk include people over the age of 50, people with chronic lung conditions, smokers, individuals on immunosuppressive medications and cancer and diabetes sufferers.

NSW Health said anyone who was in the Sydney CBD during March and April

and is experiencing symptoms should seek immediate medical attention.

One patient was simply driving through Circular Quay when they were infected.

The disease is normally contracted by inhaling contaminated water droplets or aerosolized water.

In August an outbreak in Melbourne, traced to a cooling tower, led to more than 100 cases and the deaths of two people.

Daily Mail Australia has contacted NSW Health for comment.