Avoiding food contamination

A recent spike in listeriosis cases in Australia, with four deaths, has caused alarm amongst families.

The NSW Food Authority has advised people who are most vulnerable to listeria infection to avoid eating rockmelon. A consignment of the fruit was identified as the source of the spate of illnesses after all 10 cases of listeriosis reported so far had consumed rockmelon prior to their illnesses. It is thought that listeria bacteria contaminating the rough surface of the rockmelon persisted after washing and were introduced into the fruit when cut. 

The grower voluntarily stopped supplying fruit after being notified of a potential link to illness, and any affected product has been removed from the supply chain, so consumers can be assured rockmelons currently available on shelves are not associated with this outbreak.

Listeria bacteria are gut organisms, commonly found in the soil, and sometimes water. They can contaminate some raw foods, but rarely cause serious illness in the general population. But for vulnerable people, such as the elderly, pregnant women, newborns, and those with diabetes, cancer or suppressed immune systems, listeria infections can be serious and even life-threatening.

Listeriosis usually starts with flu-like symptoms such as fever, chills, muscle aches, nausea, and sometimes diarrhoea. Symptoms emerge within a few days or even up to six weeks from eating contaminated produce.

Serious infections may cause septicaemia (blood poisoning) and meningitis (inflammation of the brain). Infection during pregnancy can lead to miscarriage, stillbirth and infection of the newborn.

Listeria bacteria are widespread and commonly carried by both domestic and wild animals. Raw meat, unpasteurised milk, raw fruit and vegetables can be contaminated with the bacteria, as can pre-prepared salads, unwashed raw vegetables, paté, cold diced chicken and pre-cut fruit and fruit salad.

To prevent listeriosis:

  • avoid high-risk foods if you are vulnerable
  • thoroughly cook raw food from animal sources, such as beef, lamb, pork, or poultry
  • wash raw vegetables and fruit thoroughly before eating
  • keep raw meat (and juices) separate from vegetables, cooked foods, and ready-to-eat foods
  • use separate cutting boards for raw meat and cooked foods and salads
  • wash your hands before and after preparing food
  • wash knives and cutting boards after handling uncooked foods
  • wash your hands after handling animals
  • store perishable foods in a cold refrigerator and wash and eat them as soon as possible.

7 March 2018
Prof David Isaacs, Infectious Diseases Consultant at The Children’s Hospital at Westmead