Listeria is a commonly found bacteria and for most people who consume foods that contain it does not cause illness.
But for elderly people, pregnant women or those with serious conditions like diabetes or cancer, it poses a serious threat.
At least 15 cases of listeriosis have been reported since authorities were first alerted to the outbreak last month.
"All 15 cases are elderly people, and most of them have significant underlying health conditions," director of communicable diseases at New South Wales Health doctor Vicky Sheppeard said in a statement Friday.
"People vulnerable to listeriosis should discard any rock melon purchased before 1 March."
The source has been linked to a farm in New South Wales state, with authorities investigating the supply chain after issuing a warning on February 23.
Listeriosis begins with flu-like symptoms including chills, fever and muscle aches. It can take up to six weeks after consuming contaminated foods for the symptoms to occur.
(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)
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