Food poisoning – common but potentially deadly

Sushi can be one carrier for the food-borne illness Listeria.


Three days of agony were the price Jessie Owens paid for not listening to her gut instinct.

The Murdoch University psychology student suffered diarrhoea and cramps after eating some salmon she bought at the market. She said she suspected something was wrong with it, but she ignored the warning bells in her head.

“I thought it was just my fear of making raw dishes at home getting better of me,” she said. “I have a weak stomach and after eating that, I had terrible cramps and diarrhoea for three days straight,” Ms Owens said.

Food poisoning is a painful but common illness that affects millions of Australians every year, caused by eating food infected with a bacteria or virus such as salmonella or norovirus. 

One of the most  dangerous is Listeria, a bacteria that affects unpasteurised dairy, raw fish such as sushi, and processed meat products. While it is usually not life-threatening, for some like the young and the elderly, or pregnant women, it can be fatal. 

A report by the US Department of Agriculture (USDA) listed Listeriosis as one of the deadliest food-borne diseases and the third most expensive, costing US$2.8 billion (AUD $3.05 billion) a year. It is a relatively rare bacterial infection, affecting about 20 Victorians each year, according to the Department of Health and Human Services. 

Listeria cane be highly dangerous for people with weak immune systems.


The Department of Health and Human Services recommends consuming high-risk food immediately after thoroughly cooking it.

Listeriosis is an illness usually caused by eating food contaminated by the bacterium Listeria monocytogenes, the bacteria are widely distributed in the environment and can grow in food at refrigeration temperatures,” a spokesperson for the DHHS said. 

Curtin University Associate Professor in Health Sciences Gary Dykes said the disease should not be treated lightly as it could potentially be deadly for people at risk.

“The bacteria generally enters the human body through ingestion with food and then can invade host cells and move throughout the body causing a range of diseases,” A/Prof Dykes said.

“Symptoms can include short term flu-like symptoms in healthy people, in at-risk individuals … symptoms could include septicaemia, meningitis and abortions. A high proportion of infected at risk individuals die from the disease.

“It very commonly occurs in the environment and is not dependent of humans for survival. This means that an agricultural food product may be easily contaminated and the bacteria can easily end up where food is prepared, including people’s homes.

“Many bacteria, including Listeria, can take many weeks to incubate in the body before disease symptoms are apparent.”

Pregnant women need to be particularly careful with Listeria.

A/Prof Dykes said prevention was the best remedy, especially for people with weaker immune systems, because treatment for at-risk individuals is a challenge. Dr Dykes also emphasized the importance of food handling – either eating out or cooking at home.

“Almost everybody would have been exposed at some time in their life. At risk groups are already vulnerable and have a lower immune system and this allows the organism to enter and move through their bodies causing the range of diseases,” Dr Dykes said.

“Treatment may entail the use of antibiotics but, because the bacteria is inside cells and patients may already be frail, treatments are often ineffective. This also add to the increased mortality.

“Prevention of contamination … needs to occur at all levels of production and preparation. This includes proper cooking, if appropriate for the food, strict hygiene and careful monitoring of production facilities.

“People often think they can tell the safety of food by looking at it but this is not the case and it may be contaminated with pathogens even if it looks fresh and healthy. A number of cases of food-borne diseases occur from a lack of hygiene at home as well.”

In Victoria this year, there have been 12 reported cases of Listeria, a slight decrease from 16 cases by this time last year. The figures were highest in 2016, with 25 cases in total, compared to the past few years, with 22 cases in 2015 and 21 cases in 2014.