Health authorities have launched a national investigation after nine cases of listeria were reported across Queensland, New South Wales, and Victoria.
Eating food contaminated with listeria monocytogenes bacteria can result in listeriosis, an illness that is particularly dangerous for pregnant, elderly, or immunocompromised people.
Although most healthy people will not become ill after ingesting the commonplace bacteria, listeriosis can be extremely serious or even life-threatening for vulnerable people.
An outbreak at a Queensland Hospital has been confirmed on Saturday, sparking fears hospitals across the state could have been exposed to contaminated food.
Mater Hospital Brisbane spokesperson confirmed “a small number of cases” have been identified at health facilities in South East Queensland.
“Affected patients have been treated in accordance with best practice,” they said.
The spokesperson said the federal government’s OzFoodNet has co-ordinated a national investigation into the outbreak following cases in NSW and Victoria.
The network monitors and responds to foodborne diseases across the country to protect Australians from food poisoning.
Queensland chief health officer, Dr John Gerrard, said authorities are investigating “several potential food sources”.
“At this stage, there is no evidence that the infection was acquired from food consumed in a hospital,” he said.
There are currently nine cases of listeria being investigated, five of which were diagnosed in Queensland.
“Queensland Health is currently the lead agency in one of three multijurisdictional foodborne disease outbreak investigations across the country due to listeria,” Dr Gerrard said.
“The source of infection is currently unknown as no single common food was able to be linked to all cases.”
He noted all four Queensland residents affected by the outbreak were over 40 years old and had underlying health issues.
Symptoms of listeriosis can take up to two months to manifest after exposure to listeria.
Dr Gerrard stressed the number of listeria cases reported in Queensland were “not above average”.
“Although listeria is uncommon, we do see a small number of cases every year,” he said.
“While we will endeavour to identify the source of every infection, it is not uncommon for this to prove unsuccessful.”
NSW issued an urgent warning earlier this month following the detection of “several confirmed cases of listeria infection”.
The Victorian Department of Health acknowledged there are currently “a number of clusters” of listeria in the country but refused to comment on the number of cases within its borders.
“Victoria is liaising with the Commonwealth and other States and Territories to investigate and manage these clusters,” the spokesperson said in a statement.
The outbreaks come after NSW Health expressed concern about an alarming increase in the number of listeriosis cases detected in the community over the past year.
“Already in 2023, we’ve recorded 25 cases of listeriosis among NSW residents, which is more than we usually expect to see in a whole year,” NSW Health branch director Kiera Glasgow said.
Listeriosis infection usually starts with fever and muscle aches.
In high risk people, it can quickly spread to the blood or central nervous system, causing sudden onset of fever, intense headaches, stiff neck, confusion or delirium, convulsions, loss of balance or coma.
People who are susceptible to infection are urged to avoid food such as ready-to-eat processed meats, soft cheeses, pre-prepared salads, raw vegetables, pate, and shellfish.