Martin D'Agostino, Virologist
With around 200,000 cases per year in England and Wales, virus-related foodborne illness is becoming a major cause for concern. Research at Campden BRI is looking to locate gaps in current knowledge on the efficacy of controls against viruses, and establish the stability of infective foodborne viruses after exposure to control measures – focusing on norovirus and hepatitis A virus.
In our latest 'talking head', Martin D'Agostino discusses the issues.
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The viruses of main concern to the food industry are human norovirus, hepatitis A and hepatitis E viruses. In the case of norovirus and hepatitis A the main supply chains at risk are fresh and frozen produce such as soft berry fruits and salad vegetables, also ready-to-eat foods and bivalve shellfish. Whereas the supply chain most at risk from hepatitis E is the pork supply chain.
Unlike bacteria viruses are inherited particles which cannot multiply on the surface of the food that contaminate, rather they are transferred onto the surfaces of food by external factors meaning that the food themselves can become carriers of the virus. In the case of fresh produce, the most likely roots of contamination are from infected handlers and sewage contaminated irrigation waters. Ready-to-eat foods might become contaminated if handled by infected food handlers. In the case of hepatitis E minimally processed pork products can become contaminated with the virus and pork meat which is eaten raw or undercooked might cause infection.
There are several challenges posed by foodborne virus is the food industry, perhaps the most challenging question which needs to be addressed is - how do we prevent the viruses entering the food chain and contaminating food in the first place? Since norovirus and hepatitis A are carried in the human gut and can be shared in large quantities by an infected individual good hygienic practices are crucial to prevent further spread. The main problem is the low infective dose of these viruses, so it really only takes a very small number of virus particles to potentially cause an infection and, since viruses are so much smaller than bacteria, hands of an infected individual, if not washed thoroughly with soap and warm water after having, for example, visited the toilet, can spread viruses onto the surface as the touch including taps, door handles, work surfaces, utensils and, of course, the fresh produce itself.
Other routes of contamination maybe the water which is used to irrigate the fruit or salad crop, for example, is potable water being used for this purpose or is a potentially contaminated river or ditch water being used for irrigation? Is untreated manure being put on to the crops? In the case of shellfish are they being harvested in waters which are free from sewage contamination? Those are the sorts of challenges facing the industry right at the start of the supply chain. Following on from that is how the produce is handled, for example, are there good sanitary facilities on the fruit farms? If there are, do the farm workers use them properly? Is there an awareness of the issues surrounding food borne viruses in the form of sufficient training of farmworkers?
Another big challenge is the fact that most of the foods which can be affected by contamination with norovirus and hepatitis A virus are not treated or processed in any way. For example, the lettuce you buy off a supermarket shelf may not necessarily have been washed, just packaged and sold. Berry fruits are not usually treated in any way so they will be picked and put straight into packaging and sold and consumed. So, in addition to preventing contamination in the first place, there is a need to know how various treatments may have an effect on the infectivity of the virus for hepatitis E there's not really enough know yet about effective control measures. However, it is generally understood that pork meat should be thoroughly cooked all the way through.
At Campden BRI we are committed to ensuring the food industry is made aware of the challenges and issues surrounding foodbourne viruses, as does generally appears to be a lack of awareness at the moment in the food industry and questions over which control measures are effective. Education is a key part of this so ensuring that the industry's kept up-to-date with key findings in the scientific community is important through member interest group presentations and virus-related seminars.
Also, since there is no readily available culturing system for the viruses in question, where the effect of processes on infectivity can be measured, a current member subscription funded project is looking at the effect of control processes using surrogates which are viruses that resemble the target viruses but which can actually be reproduced in the laboratory, which is producing some very interesting data. Also, we will be validating a method for the detection of norovirus and hepatitis A in berry fruits and salad vegetables, which can help support the industry in identifying areas in the supply chain which might be at risk of contamination. Although there is a general feeling that it would be most advantageous to know if the viruses detected are infectious or not, in the case of berry fruits and salad vegetables, just detecting the genetic material of these viruses is enough to show that there might be a problem somewhere along the supply chain since norovirus and hepatitis A are not natural contaminants of these products.