A 49-year-old woman was diagnosed with legionnaire's disease yesterday in what appears to be a fourth case arising from contaminated air conditioning systems near the Moonee Ponds shopping strip. Victoria's Chief Health Officer, Dr Graham Rouch, said the woman was admitted to the Royal Melbourne Hospital with the disease. Two cooling towers in the Moonee Ponds shopping precinct were identified as containing legionella bacteria and disinfected a fortnight ago.