SABRA LANE, PRESENTER: A health scare linked to frozen berries has deepened this evening with four new cases of hepatitis A identified in Queensland. And this is unlikely to be the end of the story, with incubation times of up to 50 days for hepatitis A, meaning new cases could be weeks away.

Health authorities say the infection was caused by poor sanitary standards at a processing factory in China.

The incident has highlighted concerns about Australia's food security, with more and more of our produce coming from overseas.

Dylan Welch reports.

DYLAN WELCH, REPORTER: It's the height of berry season and the small juicy fruit appear delectable. But these berries have been linked to an unfolding public health scare.

Health authorities moved quickly when they learnt of four cases in Victoria and New South Wales of hepatitis A, a disease normally picked up overseas.

FINN ROMANES, VICTORIAN HEALTH DEPARTMENT: So we looked into those - further looked into those cases and discovered that amongst those who hadn't travelled, the only common link was the consumption of this product of the one kilogram Nanna's Fresh Frozen Mixed Berries.

DYLAN WELCH: Late today, news broke of more infections associated wth the frozen berries.

SONYA BENNETT, QUEENSLAND HEALTH: Today in Queensland, we have identified that we have three cases of hepatitis A that are confirmed and have consumed that particular product as well.

DYLAN WELCH: That number has now increased to four.

Nanna's Berries are sold across Australia through Coles, Woolworths and IGA. Over the weekend, the berries were pulled from supermarket shelves. The supermarket recall has since been extended to include another brand, Creative Gourmet Mixed Berries.

The recalled berries were grown in Chile and China and processed in the Eastern Chinese province of Shandong.

The hep A outbreak has fuelled fears regarding health risks associated with imported foods.

PETER COLLIGNON, INFECTIOUS DISEASES, ANU: We know in rivers in both Vietnam, India and in China, there's essentially E. coli germs that for practical purposes are untreatable. Now if they get on to foods that we import, and particularly if we have them without cooking them, well, that means we have these untreatable super bugs in our bowel that might cause us a serious problem if we're unlucky enough to get sick.

ALAN KIRKLAND, CHOICE: It's not uncommon to see products go through a range of steps in different countries and it' really quite unbelievable that you would actually be flying or shipping berries around the world, but that's in reality how it does often happen. An importer might at some parts of the year import from Chile, another time from China, and as a consumer, you don't know where the stuff is actually coming from.

DYLAN WELCH: In an increasingly globalised world, more and more of the food we eat comes from overseas. Professor Collignon says some overseas food safety standards are lower than domestic products.

PETER COLLIGNON: It's taken for granted that people follow standards, but we know that's not always the case. So we need I think to have more enforceable rules that not only here are the standards, but we're doing independent testing, be it a world organisation that does it or our own government-sponsored institutions, that show us that in a reasonable sample we have looked for this. Yes, you've told us you've done it, but we've done independent testing and it says no, there is no faecal material in this food.

DYLAN WELCH: It's not the first time snap-frozen berries have been linked to health scares. There have also been outbreaks in Europe and the United States.

Frozen berries are particularly prone to carrying bacteria because they are washed in potentially contaminated water and then snap frozen.

PETER COLLIGNON: In the laboratory, that's how we preserve bacteria and viruses, we freeze them. So if you then just thaw them and eat them, well those viruses and bacteria are there. They get into your mouth, get into your bowel, and depending on the numbers there, can make you sick with either hepatitis A or a resistant bacteria or something else.

DYLAN WELCH: Nanna's Berries and Creative Gourmet are owned by Patties Foods. They declined interviews today. The Food and Grocery Council defended the industry.

GARY DAWSON, AUST. FOOD & GROCERY COUNCIL: I think first of all, the priority is quite rightly on the health and wellness of consumers and that's why the company's acted very quickly, it's worked with health authorities, it's worked with retailers to get that information out there, get the recall happening, isolate the stock.

ALAN KIRKLAND: It has been really good to see the food recall notices go out so quickly, but ultimately, this shouldn't have happened in the first place. So, a company that's importing food should make sure at the outset when it enters a supply agreement that the food is safe, but it should also be checking from time to time to make sure there are no risks in that food, and it appears that that system has broken down if we've got two brands recalled within a matter of days.

DYLAN WELCH: Hepatitis A has a 50-day incubation period and it could take weeks before people show symptoms.

SONYA BENNETT: I think we will expect to see more cases and I think that will happen throughout the country.

DYLAN WELCH: And with Australian signing an increasing number of free trade agreements with China, the United States and other countries, the potential for more food contamination outbreaks will grow.

PETER COLLIGNON: While we may think this isn't a developing country, how does it affect us?, the more we have globalisation, the more we have travel, the more we send food around the world, the more this will occur to us.

SABRA LANE: Dylan Welch reporting.