Consumers have been warned that a listeria outbreak could happen again, with pregnant women and the elderly warned to avoid rockmelon altogether in their summer fruit salads.

A major listeria outbreak between January and April this year led to the death of seven people and a miscarriage.

The Food Authority NSW’s investigation into the outbreak, released on Friday, revealed that heavy rainfall in December followed by dust storms “significantly increased” the amount of listeria on fruit.

The report stated that the farm linked to the listeria outbreak, Rombola Family Farms, has now made “extensive modifications to equipment and the packing line itself, and changes to cleaning procedures and documentation”.

But it noted that its hygiene practices were “on par with or better” than most other farms in Australia.

This has led some to question whether Australia is at risk of a listeria outbreak occurring again in the future.

Australia could again face a listeria outbreak

Professor Martyn Kirk, an expert in the spread of diseases by contaminated foods, said the report did not pinpoint how the listeria got there in the first place.

Consumers are advised to clean the skin of the rockmelon and wash the knife after slicing. Photo: Getty

“It could happen again,” he said.

“But hopefully it won’t, the industry is taking food hygiene very seriously after the outbreak this year.”

Listeria is a type of bacteria found in soil, animal manure and water.

Rockmelon is not the only food susceptible to containing listeria, although the rough nature of its skin means dirt is more easily trapped even after cleaning processes.

Other foods at higher risk of being contaminated with listeria include processed meats, smoked salmon, chilled seafood, soft cheeses, sashimi and soft serve ice cream, according to Food Standards Australia.

Professor Kirk said there are about 150 foodborne disease outbreaks every year (such as salmonella) of which one to five are due to listeria.

There are 70 to 80 people who get listeria infections every year such as blood poising or meningitis.

“The proportion of people who die from Listeria infections is around 20 per cent.

“The main reason that there are a high proportion of people dying is that they are often older, and usually are sick with other illnesses such as cancer.”

Gastroenterologist Dr Vincent Ho agreed that while changes have been introduced to reduce the chance of an outbreak happening again, it “cannot completely eliminate the risk”.

Public health expert Dr Katherine Todd said listeria is impossible to identify by looking at or smelling the food.

“Consumers should rub the skin of rockmelon clean to get rid of any residual dirt,” she said.

“It’s also important to clean the knife you use to cut rockmelon, before slicing other fruits for a fruit salad, or you could transfer listeria to other foods.

“The elderly, pregnant women and anyone with a suppressed immune system such as someone with a chronic illness should not eat rockmelon.”

Rockmelon industry responds to investigation

Australian Melon Association’s Dianne Fullelove said it is important for consumers to keep in mind that there is a risk of any food carrying a foodborne disease.

“For most people, rockmelon is perfectly safe, as is camembert cheese,” she said.

“The melon industry has been working very hard over the last eight months to ensure that nothing like this incident occurs again.

“The industry has introduced a new grower-funded project that provides individual guidance on food safety for rockmelon growers.

“We have sent microbiologists to every packing shed and they are taking swab tests as an extra safety measure.”