Understanding Food-Borne Pathogens

The most common food-borne pathogens in Australia are bacteria, viruses and parasites.
October 15, 2019

Food contaminated by harmful microorganisms can make people very sick. By law, food businesses and workers share the responsibility to protect their customers from food-borne illness (‘food poisoning’) and other health risks.

Unfortunately, four million cases of food-borne illness occur in Australia every year, many of which are caused by unsafe food handling practices that allow dangerous bacteria, viruses and parasites to contaminate food. 

What is bacteria?

Bacteria are common causes of food-borne illness. Under the right conditions, bacteria can multiply rapidly, doubling in number roughly every 20 minutes.

The most common disease-causing bacteria in Australia are Campylobacter, Salmonella, Listeria and E. coli. The foods that most commonly harbour these dangerous bacteria include meat, poultry, eggs, unpasteurised milk and cheese, shellfish and leafy green vegetables.

Most people who become infected with pathogenic bacteria will experience mild symptoms of gastroenteritis, such as diarrhoea, abdominal pain, fever, nausea and vomiting. However, some people will experience more severe symptoms, which could result in hospitalisation or death.

While rare, food-borne bacterial infections can cause serious complications or long-term health consequences. E. coli, for example, is commonly found in ground beef, unpasteurised dairy products and fresh produce. Among other life-threatening complications, E. coli infection can cause hemorrhagic diarrhoea, Hemolytic Uremic Syndrome (kidney failure) and Thrombotic thrombocytopenic purpura (blood disorder).

Most bacteria in food can be killed by cooking food to the required temperature; however, some bacteria can develop a shell that can protect them from extreme heat or cold (called ‘spore-forming bacteria’), and some produce toxins that aren’t destroyed by the cooking process. Staphylococcus aureus, Bacillus cereus and Clostridium perfringens are examples of common toxin-producing bacteria in Australia.

When food spends too much time in the Temperature Danger Zone (5°C – 60°C), it can become contaminated with high levels of toxins, which remain in the food even after the bacteria have been destroyed. Freezing food stops bacteria from reproducing, but it does not kill bacteria.

What is a virus?

Viruses are another common cause of food poisoning in Australia. Norovirus, for example, is highly contagious and a leading cause of gastroenteritis in Australia (and around the world). Hepatitis A, a virus that affects the liver, has caused a number of food-borne illness outbreaks in Australia in recent years.

Typical symptoms of viral infections include diarrhoea, vomiting, nausea, stomach cramps, fever, chills, headache and muscle aches. Most people will recover from a viral infection within a few days, but vulnerable groups — including young children, the elderly, pregnant women and people with impaired or weakened immune systems — are at greater risk of developing serious or fatal complications.

Viruses need a living host to survive and reproduce, but they can travel on any type of food, including traditionally low-risk foods like baked goods and dehydrated, preserved and processed foods (e.g. biscuits, crackers, sweets).

Viruses can survive on virtually any surface and are extremely resistant to hot and cold temperatures, which means they aren’t destroyed or rendered inactive by cooking, refrigerating or freezing.

Viruses are most often passed to customers from infected Food Handlers who don’t practise good hygiene — such as frequent and thorough hand washing — or who do not follow safe food handling procedures to prevent food contamination.

What are parasites?

Parasites, such as tapeworms and roundworms, are organisms that live on or inside humans or animals. They are excreted in faeces and can contaminate meat during slaughter and fruit and vegetables grown in soil fertilised with manure.

People get parasites by consuming contaminated food or water, though transmission is rare because the majority of farm animals are treated to prevent parasitic infections. However, parasites such as anisakiasis — caused by eating parasite-contaminated seafood — and Cyclospora, a non-native parasite linked to some imported foods, have caused a number of illnesses and outbreaks in Australia.

Food-borne parasites are difficult to get rid of; symptoms may including abdominal pain and bloating, nausea, vomiting, fatigue and dizziness. Rarely, they can cause more serious complications like digestive bleeding, bowel obstruction and perforation.

Most parasites can be killed by thoroughly cooking food (75°C or above is recommended) or by freezing. Fish intended to be used as sushi or sashimi should always be bought frozen from a reputable supplier.

How to prevent food-borne illness

Most cases of food poisoning are caused by poor hygiene, ineffective cleaning and sanitising or inadequate time and temperature control.

Under federal law, Food Handlers in any establishment or industry that serves food to the public must be trained to handle food safely. This includes fundamental food safety concepts and best practices, such as:

  • safe food preparation
  • safe food storage
  • preventing cross-contamination
  • cleaning and sanitising
  • good personal hygiene

In most states and territories in Australia, food businesses are also legally required to employ a Food Safety Supervisor to take control of food safety in the business. Food Safety Supervisors must complete a nationally recognised Food Safety Supervisor course, such as the online course offered by the Australian Institute of Food Safety (AIFS).

These laws are in place to protect the public from food-borne illness, but they also protect food businesses and organisations from the serious legal and financial consequences of causing food-borne illness or a food-borne illness outbreak.

Contact AIFS to learn more about food safety.