Frozen mixed berries exported from China were found associated with the Australian Hepatitis A incidents earlier this year.
(ABC: Mark Doman, 2015)
Indeed, viral contamination of berries is nothing new. One of the earlier reported Hepatitis A outbreaks occurred in Scotland in 1980s, and linked to consumption of raspberry mousse prepared from frozen raspberries.
In Hong Kong, it is also recently rumoured that some people fell ill with Hepatitis A after eating blueberries bought from a local supermarket store. The Centre for Health Protection (CHP) has clarified that there’s no epidemiological link between rise in Hepatitis A infection this year and eating blueberries.
However, the government is criticized for not conducting routine testing for Hepatitis A virus in berry products sold in Hong Kong.
Does Routine Surveillance Help?
In 2010, Food Standards Australia New Zealand (FSANZ) once examined the usefulness of routine testing for viruses in food. The conclusion is that routine testing is of limited use because:
The virus in contaminated food is usually present at such low levels the pathogen can’t be detected by available analytical methods.
The virus can be unevenly distributed and a result can be negative but food can still be unsafe.
A positive result can come from the presence of genomic material from inactive or non-infectious virus in the food, but this doesn’t mean the virus is active.
Risk-based Testing during Outbreaks
Instead of classifying Hepatitis A virus as a routine food test item, Australian food safety authority relies on epidemiological data to identify “suspected food commodities” and determine their risk levels, as well as for traceback purpose. For example, imported berries from facilities in question will be subject to 100 per cent testing at the border.
Molecular detection methods (e.g. RT-PCR) have been used by many regulatory laboratories and specialized commercial laboratories to rapidly analyse suspected food for Hepatitis A.
These methods are ideal for the detection of viruses with low titers and useful for fast screening samples during outbreaks and even for routine surveillance.
Prevention of Food Contamination
Apart from fruit and fruit juices, cold cuts and sandwiches, milk and milk products, vegetables, salads, shellfish, and iced drinks are also commonly implicated in Hepatitis A outbreaks. Contamination can occur throughout the production, processing and transportation of produce e.g. transfer of virus from contaminated hands to food and food contact surfaces.
In order to safeguard food safety, food testing is essential but not the only tool. Good agricultural practice (GAP) and good hygiene practice are the keys in prevent viral contamination of foods along the food supply chain e.g. using treated manures and high-quality irrigation water for agriculture, using potable water for making ice or washing produce after harvesting, cleaning & sanitizing equipment and transportation vehicles, providing sanitation facilities for workers, checking worker health, etc.
Remarks - Facts about Hepatitis A
(FDA Bag Bug Book, 2013)
Hepatitis A virus cannot grow in the environment (e.g. food and water) outside a host cell, but extremely stable under a wide range of environmental conditions (e.g. freezing, heat, chemicals, and desiccation)
Concentrations of disinfectants commonly used against pathogenic bacteria are not considered effective against these viruses.
Cooking food until it’s at a temperature of 190˚F (87.8oC) in the middle for at least 1½ minutes or boiling food in water for at least 3 minutes inactivates the virus.