A patient at Brisbane's Mater Hospital has tested positive for legionella after undergoing three medical tests, the second case in the city this month.

A patient at Brisbane's Mater Private Hospital has tested positive for the legionella bacterial infection, the second case of the deadly disease in the city's hospitals this month.

The patient returned a positive result from one of three medical tests, the hospital confirmed on Monday.

"Mater has advised Queensland Health of these preliminary findings and has commenced precautionary measures to conduct additional water tests, and has commenced disinfection," a statement said.

It is unknown whether the patient contracted the infection at the hospital.

It comes three weeks after a palliative patient at Wesley Hospital tested positive for legionella pneumophila.

Bacteria that cause the disease were found in an ice machine.

Since an outbreak in 2013 at Wesley Hospital where a patient died, Queensland hospitals and nursing homes have been required by law to conduct regular water tests for the bacteria.

Legionella pneumophila thrive in warm water and in man-made environments including pipes and plumbing.