Health Advisory on Australia's Rock Melons Listeria Outbreak

On 2 March 2018, Australia reported that rock melons implicated in an ongoing outbreak of Listeria monocytogenes infections in Australia had been exported to Singapore. Imported from a New South Wales grower, the fruits were sold in Sheng Siong supermarket outlets and wet markets between Feb 12 to March 2. The Agri-Food & Veterinary Authority (AVA) has worked with importers to remove the remaining unsold rock melons. There has been no further import of rock melons from the affected grower since, and import has been suspended.  To ensure food safety, AVA has also taken samples of locally sold rock melons for food safety tests, including testing for listeria. The results are pending.


Listeria is a type of bacteria which causes Listeriosis (listeria infection). The bacteria is found widely in the environment in soil, water, effluents and the faeces of humans and animals. Food items, which could be contaminated by the bacteria include raw or ready-to-eat foods, such as raw (unpasteurised) milk or raw meat and their products, seafood, and fresh produce including fruits and vegetables. Unlike many other germs, listeria can grow in the cold temperature of the refrigerator. Listeria is killed by cooking and pasteurization.

Symptoms of Listeriosis

The symptoms of listeriosis include fever, muscle aches, stiff neck, and sometimes nausea or diarrhea. The incubation period of Listeria ranges from 3 to 70 days (typically 1 – 4 weeks). Pregnant women, new born babies, adults above the age of 65 and people with compromised immune system are more prone to this infection which may lead to death. For pregnant women, listeriosis can cause complications in the fetus or newborn.

Diagnosis, Treatment, and Prevention

Listeriosis is diagnosed by laboratory testing of blood, cerebrospinal fluid, or stool samples. If diagnosed early, listeriosis is treatable with antibiotics. There is no vaccine for listeriosis. However, listeriosis can be prevented by proper food handling practices.

Protect yourself from listeriosis by following these food safety tips:

  • Thoroughly wash raw vegetables, fruits, and raw food from animal sources before consumption.
  • Keep uncooked meats separate from vegetables, fruits, cooked and ready-to-eat food.
  • Avoid eating unpasteurized dairy products.
  • Wash hands and kitchen utensils such as knives and cutting boards especially before and after handling raw food.
  • Clean your fridge regularly.