CONSUMERS are being warned to check their fridges and discard suspect soft cheeses as casualties mount in Australia's biggest ever listeriosis outbreak, the precise cause of which remains a mystery.
In NSW, a further three cases of the bacterial illness have been identified, bringing the national total to 21. A 34-year-old woman in NSW has miscarried and two men - an 84-year-old Victorian, and a 44-year-old Tasmanian - have died. Each of the new cases have been in people aged over 65, and one of them is in a serious condition.
The Victorian Department of Health has identified a ''definitive'' link between the outbreak and batches of brie, camembert, blue and other soft cheeses manufactured by the Jindi Cheese company at its Jindivick factory in Victoria, the state's acting chief health officer, Dr Michael Ackland said.
''Of course it is very bad news'' said Jindi Cheese's head cheesemaker and CEO Franck Beaurain. But he referred to the Department of Health's media statement that ''it is not possible to absolutely rule in or out a link for these deaths to Jindi''.
The illness is caused by the widespread pathogen Listeria monocytogenes which can affect a range of food products, notably soft cheeses, pre-prepared salads, unwashed raw vegetables, paté´, cold diced chicken and pre-cut fruit.
Pregnant women, older people and those whose immune systems are compromised are particularly susceptible.
The Jindi company has issued a ''precautionary'' and ''voluntary'' recall of all cheeses it made before January 7. This takes in more than 100 products sold under several brand names including Jindi, Wattle Valley, Coles Finest and Harris Farm with use-by dates ranging from February 17 to April 4 and distributed throughout Australia and internationally.
Mr Beaurain said there had been no change to the company's manufacturing procedures but that Jindi had increased its safety testing ''just to be sure the cheeses on the market are completely safe''.
The recall was made ''only because of the Department of Health's instructions … I follow the Department of Health instructions since January 16 and will continue to do so,'' Mr Beaurain said.
Dr Ackland said Victorian Health Department officials after visiting the factory on January 16 were ''satisfied that appropriate food processing, hygiene and monitoring practices were being followed for the manufacture of products from January 7''.
But what went wrong in the factory before January 7 remains a mystery.
A Victorian Department of Health spokesman said ''despite the best practices, these things can happen''.
''Normally cheese doesn't make people sick,'' said Dr Kari Gobius, leader of food safety at the CSIRO. ''We have to presume something went wrong, even if what went wrong can't be immediately identified''.
He said possibilities included a strain of the bacteria resistant to the usual safety protocols, a deteriorated batch of disinfectant used to clean equipment, or a change to normal refrigeration processes.
The listeria germ is unusual because it continues to thrive even at fridge temperatures. It can cause blood poisoning and meningitis.
Further cases of illness are possible because the bacteria has a 70-day incubation period.
There are typically 20 to 30 cases of listeriosis reported in NSW each year but most are isolated and outbreaks are unusual. Early symptoms include fever, headache, tiredness, aches and pains, but the illness is readily treatable with antibiotics if identified early.