A third person has died in the national listeria outbreak linked to rockmelon grows.

There are now 15 reported cases and authorities have issued a warning to people most vulnerable to listeria infection including elderly, pregnant or immune compromised to avoid eating rockmelon and to discard the fruit if they have it at home.

Four of the additional cases are from Victoria and one is from Tasmania. The onset of their illness occurred the week after the initial 10 cases.

“All 15 cases are elderly people, and most of them have significant underlying health conditions,” Director Communicable Diseases NSW Health, Doctor Vicky Sheppeard said.

“Six of these cases, including two of the people who died, are from NSW.

“We can confirm that 13 of the 15 cases consumed rockmelon before the onset of their illness. People vulnerable to listeriosis should discard any rockmelon purchased before 1 March.”

A third person has died at least 15 people have fallen ill as a national listeria outbreak linked to rockmelon grows.

Listeria can be extremely serious and even life-threatening for vulnerable people.

The outbreak has been linked to a grower in Nericon in the Riverina region of New South Wales.

The company promptly ceased production last week after being notified of a potential link to illness and is working with the authority to investigate how the cantaloupes were contaminated.

Listeriosis starts with flu-like symptoms such as fever, chills, muscle aches, nausea, and sometimes diarrhoea. The symptoms can take a few days or even up to six weeks to appear after eating contaminated produce.