NSW Health responds to all outbreaks in accordance with the standard process and procedures as outlined in the NSW Infectious Control Guidelines that have been in place for more than 15 years. When a food borne outbreak affects more than one state or territory, the Australian guidelines for multi-jurisdictional outbreak investigations are also followed.

NSW Health takes outbreaks very seriously, and immediately investigates to identify likely sources and put in place alerts to protect public health.

In this specific case, NSW Health issued a preliminary warning about listeriosis on Friday, 23 February, including advice that vulnerable people avoid risky foods including rockmelon.

As soon as the investigation indicated rockmelon from the Griffith area was the likely source, the NSW Food Authority issued a warning on Wednesday, 28 February.

Whenever listeriosis is diagnosed in a patient, it must be reported to NSW Health, and the patient or carer is interviewed to establish the food that has been consumed up to the last 70 days from onset of the infection.

The identification of a source involves interviews with multiple patients, specialist laboratory testing of patient samples, traceback of the source of food eaten and special testing of suspected foods.

Trained epidemiologists then thoroughly investigate all patients, arrange specialist testing, and work with the NSW Food Authority to find potential links between cases.

NSW Health expresses its sympathy to those affected by the outbreak, but reassures the community that all appropriate process and procedures were followed.