Reservoirs of the tissue-necrotising infection that causes Buruli ulcer may have spread to metropolitan Melbourne, with three cases diagnosed in the city’s northwest, health authorities warn.

Victoria’s chief health officer Professor Brett Sutton flagged on Tuesday that three cases of Myocbacterium ulcerans infection had been notified from Essendon, Moonee Ponds and Brunswick West.

The patients had all travelled through areas where the bacteria were endemic, such as the Mornington and Bellarine Peninsulas.

But health authorities said genetic analysis suggested the cases were linked by a single, unknown source in Melbourne.