Following recent diagnosis of several cases of Legionnaires' disease in South Eastern and South Western Sydney Local Health Districts, NSW Health is reminding building owners and occupiers to ensure air-conditioning cooling towers are properly maintained.

Dr Adi Vyas, Acting Director, Environmental Health, Health Protection NSW, said while local councils were on the frontline of compliance, the onus was on businesses to remain vigilant.

"We do not want to see an increase in Legionnaires' disease notifications following the restarting or intermittent use of cooling towers as people return to their workplaces," Dr Vyas said.

"Businesses reopening office space should ensure their cooling tower servicing regimen is up to date and disinfection procedures are operating correctly.

"Where there is any possibility that a system is not operating correctly, it should be cleaned and an online disinfection procedure undertaken as soon as possible."

Legionnaires' disease is a severe and sometimes life-threatening form of pneumonia caused by Legionella bacteria.

NSW Health has produced extensive guidance on managing risk factors associated with the seasonal operation of cooling water systems and managing shut down periods, available at Guidelines on Legionella control.

For further information please contact your local Public Health Unit on 1300 066 055.