What is Listeriosis?
Listeriosis is a serious bacterial infection caused by Listeria monocytogenes. It’s a type of foodborne illness, meaning it’s typically contracted by consuming contaminated food. While listeriosis is less common than other foodborne illnesses such as salmonella or E. coli infections, it poses a higher risk of severe illness — especially among vulnerable populations.
In Australia, listeriosis is a notifiable disease, meaning confirmed cases must be reported to health authorities. Although outbreaks are relatively rare, they can have serious public health consequences, particularly in hospitals, aged care facilities, and food production environments.
Understanding Listeria monocytogenes
Listeria monocytogenes is a hardy bacterium found in soil, water, decaying vegetation, and animal faeces. It can contaminate a wide range of food products — particularly those that are ready-to-eat or refrigerated, such as deli meats, soft cheeses, and pre-packaged salads. Listeria can grow even at fridge temperatures, which makes it especially challenging to control.
How Listeriosis Develops in the Body
Once ingested, Listeria monocytogenes can survive stomach acid and enter the bloodstream. From there, it can spread to the brain (causing meningitis) or cross the placenta in pregnant women, risking miscarriage, stillbirth, or neonatal infection. In healthy individuals, the infection may pass unnoticed or cause only mild illness, but in high-risk groups, it can lead to life-threatening complications.
Who is at Risk of Listeriosis?
While anyone can contract listeriosis, certain groups are more likely to experience severe illness.
Pregnant Women and Listeriosis Risks
Pregnancy weakens the immune system, making it easier for Listeria to bypass normal defences. Although pregnant women may only experience mild flu-like symptoms, the infection can cross the placenta, potentially leading to miscarriage, premature birth, or stillbirth.
People with Weakened Immune Systems
Individuals undergoing chemotherapy, organ transplant recipients, and people with conditions such as diabetes or HIV/AIDS are at greater risk of invasive listeriosis. The infection can spread rapidly in these individuals, often requiring hospitalisation.
Older Adults and Vulnerable Workers
People over 65 are at higher risk due to a natural decline in immune function. Those working in aged care, healthcare, or food service — particularly first-time workers unfamiliar with food safety protocols — should be especially vigilant.
Symptoms of Listeriosis
Early Symptoms
Initial symptoms usually appear within a few days to a few weeks after exposure and include:
- Fever
- Chills
- Muscle aches
- Nausea
- Diarrhoea
Anyone in a high-risk group who experiences these symptoms — especially after eating high-risk foods — should seek medical attention promptly.
Advanced Symptoms and Complications
If the infection spreads beyond the digestive system, it can lead to:
- Headache
- Stiff neck
- Confusion
- Loss of balance
- Seizures
- Meningitis or septicaemia
These severe outcomes require immediate hospital treatment.
How is Listeriosis Diagnosed and Treated?
Medical Diagnosis
Doctors diagnose listeriosis using blood or cerebrospinal fluid (spinal tap) tests to detect the bacteria. A thorough patient history — including recent dietary habits — helps narrow down the cause.
Treatment Options
Listeriosis is typically treated with antibiotics, such as ampicillin or gentamicin. Hospitalisation is often necessary, especially for high-risk patients. Pregnant women are also given antibiotics to reduce the risk of passing the infection to the baby.
Recovery may take weeks, depending on the severity and individual health status.
How to Prevent Listeriosis in Everyday Life
Food Safety Tips at Home and Work
To reduce your risk:
- Wash fresh produce thoroughly
- Avoid unpasteurised milk and dairy products
- Cook food to safe internal temperatures
- Reheat leftovers until steaming hot
- Clean kitchen surfaces and utensils properly
- Store perishable foods below 5°C
Foods to Avoid if You’re in a High-Risk Group
High-risk individuals should avoid:
- Deli meats and pâté unless reheated to steaming hot
- Soft cheeses (e.g. brie, camembert) unless made from pasteurised milk
- Pre-packaged salads and cold seafood
- Raw sprouts
Safe Food Storage and Handling
Good practices include:
- Checking use-by dates
- Keeping fridge temperatures at or below 5°C
- Storing raw and cooked food separately
- Using clean containers for leftovers
Listeriosis and Food Recalls in Australia
How Food Recalls Work in Australia
Food recalls are managed by Food Standards Australia New Zealand (FSANZ) and state authorities such as NSW Health. When contamination is detected, FSANZ issues a public notice, and affected products are removed from shelves.
What to Do if a Food Recall Affects You
If you’ve purchased a recalled product:
- Do not consume it
- Follow instructions for return or disposal
- Watch for symptoms for at least 70 days after exposure
- Contact your GP if symptoms appear
When to See a Doctor and What to Expect
Seek immediate medical attention if you:
- Are in a high-risk group and experience flu-like symptoms
- Have eaten a recalled product and feel unwell
- Show neurological signs such as confusion or stiff neck
Your doctor may recommend diagnostic tests and initiate antibiotic treatment based on the findings.
Listeriosis in the Workplace
Food Industry Roles
Employees handling food — such as kitchen staff, caterers, and food packers — must follow strict hygiene protocols:
- Regular handwashing
- Wearing gloves and PPE when required
- Preventing cross-contamination
- Monitoring fridge temperatures
Supporting Colleagues at Risk
Encourage workplace awareness through:
- Training sessions on food safety
- Clear reporting procedures for symptoms or illness
- Support for employees recovering from infection, including time off and gradual return-to-work plans
FAQs
What causes listeriosis?
Listeriosis is caused by the bacterium Listeria monocytogenes, usually found in contaminated food.
How do you get listeria infection?
By eating food contaminated with Listeria, especially ready-to-eat products stored in the fridge.
What are the first signs of listeriosis?
Fever, chills, muscle aches, nausea, and diarrhoea.
How serious is listeria infection?
It can be mild in healthy people, but life-threatening for pregnant women, older adults, and immunocompromised individuals.
Who is most vulnerable to listeriosis?
Pregnant women, people over 65, and those with weakened immune systems.
Can listeriosis be cured?
Yes, with early diagnosis and antibiotic treatment.
How long does listeria stay in your body?
Symptoms may appear up to 70 days after exposure. In severe cases, recovery may take weeks.
What foods are linked to listeriosis outbreaks?
Deli meats, soft cheeses, cold seafood, pre-packaged salads, and unpasteurised dairy products.
Is listeriosis contagious between people?
No, it is not spread from person to person.
How do I avoid listeriosis at work or when eating out?
Avoid high-risk foods, ensure food is cooked or reheated properly, and follow workplace hygiene practices.
Key Points
- Listeriosis is caused by Listeria monocytogenes and spreads via contaminated food.
- It can be severe in high-risk groups, including pregnant women and older adults.
- Symptoms range from mild flu-like illness to serious complications like meningitis.
- Diagnosis is via lab tests; treatment includes antibiotics and hospital care.
- Prevention is possible with proper food storage, hygiene, and workplace awareness.
- Food recalls play a vital role in protecting the public.
