Food-borne viruses are the second most important cause of food-borne outbreaks in the European Union (EU) after Salmonella. EFSA has today published a review of the latest scientific knowledge on these viruses providing advice on possible measures to control and prevent their spread in the EU. The assessment recommends among others that mitigating measures should focus on the prevention of contamination rather than removing the virus from contaminated food.
Viruses have been increasingly recognized as important causes of outbreaks of food-borne disease. In 2009, they were responsible for 19% of all outbreaks in the EU causing over 1000 outbreaks and affecting more than 8700 citizens. The total number of outbreaks caused by viruses has been increasing since 2007. Food can act as a vehicle for transmitting certain viruses to humans, which in some cases are highly contagious and may lead to widespread outbreaks.
EFSA’s scientific opinion looked at norovirus and hepatitis A viruses in fresh produce, ready-to-eat foods and bivalve molluscs such as oysters, mussels, and scallops, as these are ranked as priority hazards by the World Health Organisation. The hepatitis E virus was also assessed in the opinion as it is highly prevalent in pigs across Europe, and there is some evidence of transmission through food, although human clinical cases are rare in the EU.
According to EFSA’s Scientific Panel on Biological Hazards (BIOHAZ) effective measures to control the spread of these viruses should focus on preventing contamination at all levels of production rather than on trying to remove or inactivate these viruses from contaminated food. Thorough cooking is currently the only efficient measure to remove or inactivate norovirus or hepatitis A virus from contaminated bivalve molluscs or fresh produce. Meat or liver should also be completely cooked to ensure that possible hepatitis E infections are removed or inactivated.
The opinion gives several recommendations for measures to control the spread of these viruses in the EU as well as for further data collection. Recommendations for mitigation measures include introducing microbiological criteria for norovirus in bivalve molluscs, unless the products are labelled ‘to be cooked before consumption’ and further training of food handlers on viral contamination of foods and the environment. To prevent hepatitis E infections, the BIOHAZ Panel also recommends that people with liver diseases or immune deficiencies and pregnant women should be discouraged from eating under-cooked meat and liver from wild boar and pork.
EFSA’s scientific advice helps to inform the risk managers and may contribute to risk management measures for the control of food-borne viral infections in the EU.
Important to note in relation to the recent E. coli O104:H4 outbreaks in Germany and France in 2011: E. coli is not a food-borne virus.
On its own initiative, EFSA instigated a review of the biology, epidemiology, diagnosis and public health importance of viruses and identification of possible control options for reducing infections in order to provide up-to-date information to the EU risk managers.
Viruses can be transmitted from person to person – the most common type of transmission - or through food or water contaminated with virus-containing human waste. Any type of food can be a carrier of food-borne viruses due to the fact that it can be contaminated at the source, mainly through sewage pollution of the environment or in association with food processing and handling due to poor hygiene practices.
In humans, norovirus causes gastroenteritis -- an inflammation of the stomach and intestines. It is the most common cause of infectious human gastroenteritis in the EU. Hepatitis A and E viruses usually cause flu-like symptoms but can also lead to an acute disease of the liver.
Food safety criteria laid down in the Commission Regulation on microbiological criteria for foodstuffs define the acceptability of a product or a batch of foodstuffs. There are currently no specific food safety criteria regarding viruses in the EU but legislation foresees such criteria to be established for bivalve molluscs when sufficient analytical methods exist.