Nanna's frozen berries, along with others, linked to a plant in China and associated with a hepatitis A outbreak were recalled at the weekend.

Here's what we know:

What brands are included in the consumer recall?

The brands affected are all 1 kg packs of Nanna's brand Frozen Mixed Berries and all 300g and 500g packs of Creative Gourmet Mixed Berries, sold nationally in Coles, Woolworths and IGA supermarkets and independent stores.

Victorian Chief Health Officer Dr Rosemary Lester said four berries are in the products - strawberries, raspberries, blackberries and blueberries.

Where were they made?

All the berries were packed in China and the strawberries, raspberries and blackberries were grown in China, the blueberries were from Chile. The mixed berries were distributed in Australia by Patties, based in Bairnsdale.

What should I do with my packet of berries?

Patties, which owns the Nanna's brand, asks that consumers return the berries to the point of purchase for a full refund, rather than throwing them away.

"The only common link between the cases is consumption of this product – there is no overseas travel or common restaurant exposure.

How does hepatitis A get on food?

There are two ways it could get on food, one is soil but the other is through poor hygiene. Dr Said Ajlouni, senior lecturer in food science at the University of Melbourne, says berries do not come into contact with the ground when growing so it is an unlikely source, but dirty water in cleaning the berries could be a factor. Dr Ajlouni, however, says investigators should look to human hygiene and health as the most likely source of the contamination. The contamination may have occurred at the washing (dirty water), harvesting or processing, packaging and transportation phases, he says.

What do we know about Hepatitis A?

Dr Lester says the hepatitis A virus infection is uncommon, and normally associated with travel to countries affected by endemic hepatitis A.

Dr Ajlouni says to see hepatitis A, scientists need a microscope and a dye.

It can live on food but needs an animal or human to multiply and grow, he says. A person can spread hepatitis A when they fail to thoroughly wash their hands after going to the toilet or handling soil. Once the virus is on the body it can be transferred through contact with food, sneezing or coughing. 

It can take one to seven weeks for symptoms to show, depending on a person's immunity. Symptoms of the disease include abdominal pain, headaches, chills, fever, vomiting and yellow pallor and eyes. Thorough hand washing eliminates the virus from hands.

At least three Victorians and two NSW residents have been diagnosed with the disease after eating frozen berries.

How does it survive the deep freeze?

Viruses lie dormant under freezing conditions, Dr Ajlouni says. While he strongly recommends consumers avoid eating the frozen berries uncooked, he says it is possible to kill the virus if the berries are cooked to 90 degrees or hotter. 

Were the Nanna's berries tested before they were consumed?

The Department of Agriculture tests foods in line with the standard set by Food Standards Australia New Zealand but FSANZ does not require virus testing on imported berries. The department says state health authorities are responsible for managing post-border safety incidents.

A Patties spokesman says Patties conducts its own tests regularly and tests beyond the FSANZ standards, but could not say exactly how widely it tests. It says it is looking at the production process from the plant in China associated with the virus.

"Sampling of the product will be undertaken to identify the virus, but it is difficult to find hepatitis A virus even in a contaminated batch," Dr Lester says.

Do we grow our own berries?

Yes, Australia grows berries and they are available June to April.

Fairfax Media has calls into various sources to find out just how many berries are imported from overseas and the countries of origin.

How can I tell my product is made in Australia?

Choice, the Greens, the Victorian Farmers Federation and AusVeg, which represents Australian vegetable and potato growers, say you cannot really tell based on labelling laws what is really Australian made.

A federal Standing Committee on Agriculture and Industry's recommended changes to labelling in October last year. Last week federal Greens MP Christine Milne reintroduced a bill calling for mandatory "country of origin" labelling .

The label should have the gold kangaroo in the green triangle logo to signify it is a "product of Australia" or grown in Australia, however, how much of a product is from Australia is a bit unknown.

Consumer group Choice says the Coles website describes Creative Gourmet Mixed Berries as "Packed in Australia using imported fruit", but says that statement is "meaningless".

Choice said its survey found only 12 per cent of those polled understood what "made in Australia" means.  Choice calls for "Australian produce" or "product of Australia" labelling to mean a "significant portion" of the ingredients and virtually all processing is from the country claimed. It also says "manufactured in Australia" or packaged in Australia should relate "solely to manufacturing". It called for any change to labelling laws to be tested for simplicity with consumers.

The Victorian Farmers Federation believed it should be 75 per cent Australian-grown or made to make the claim.

VFF president Peter Tuohey says if a product is more than 30 per cent cheaper than every other "Australian" product on the shelf then there is a good chance it is mostly imported. 

Who can export frozen berries to Australia?

Frozen berries can come from any country as long as they adhere to the import guidelines, the federal Department of Agriculture says. Guidelines include that the skins and seeds are in tact and the produce is free of risky quarantine materials like soil, leaf trash, stems and bark. 

They need to be frozen at minus 18 degrees or for more than seven consecutive days, but hepatitis A can survive being frozen. The packaging has to be clean and commercially prepared.  Each consignment must have documentation verifying the freezing process.

Where do our fresh berries come from?

When we import fresh berries they mostly come from New Zealand which is able to sell strawberries, cranberries, English gooseberries and blueberries to Australia. The United States can also export strawberries to Australia. Fresh berries are required to have an import permit, be disease and pest free, be inspected on arrival and some are required to undergo mandatory treatment.