Sunday, 29 June 2014

Foodborne diseases: The case of the innocent-looking berries

'Berries' by Jeremy Cherfas
under a CC license
It's been about two-and-a-half years now that cases of hepatitis A have been appearing in Europe. Further analysis, as quoted by the European Food Safety Authority, has shown similarities in the viral genome across the majority of those cases. That is an indication for a common source of infection, which - currently - is believed to be frozen berries. So far, 11 countries in Europe are known to have been affected. (A similar-sounding story that appeared in the US seemed to be coincidental and it was attributed to imported pomegranate seeds.)

Technically, the term "berries" covers a wide variety of fruits although it is normally used to describe small, juicy, bright-coloured fruits, such as blueberries, strawberries, blackberries, blackcurrant, etc. They can be eaten raw but they are also extensively used as ingredients either raw or as preserves in other foodstuffs, such as creamy desserts, parties, flavoured ice-creams, various alcoholic beverages, etc.

In some of those products the berries find themselves in having had minimal - and sometimes non-thermal - treatment. That provides ground for pathogens and, in the case of hepatitis A, the hepatitis virus that may lie on the surface to survive.

Locations of the hepatitis A outbreaks attributed
to a common, continuous source in the EU/EEA,
possibly frozen berries; Compiled from Source:
European Centre for Disease Prevention and
Control and the European Food Safety
Authority,  2014; Outbreak of hepatitis A in
EU/EEA countries - Second update. EFSA
supporting publication 2014:EN-581. 14 pp.

Hepatitis A is a disease usually transmitted via the consumption of food or water contaminated by infected fecal matter. It has a very long incubation period that can reach up to 50 days and, in some cases, it is asymptomatic, i.e., the people infected do not display any symptoms of illness (but they can transmit the virus).

While the food law in Europe requires food businesses to keep traceability records when receiving or providing food products or ingredients to other food business operators, including retailers, linking the hepatitis A outbreaks to a particular contaminated ingredient and tracing it back to a single source has proven to be very challenging.

The main reasons for that are the long incubation period of the disease and the complexity of the food chain, especially when dealing with multi-ingredients food products. Thus, when a case of hepatitis A is confirmed, pinpointing the source of the infection would require the patient to identify foodstuffs he/ she had consumed over a very long time (up to 50 days before the onset of symptoms), an exercise that is nearly impossible to execute in a fully accurate way. Then the ingredients and the processing of the individual foods needs to be considered in order to select the ones likely to have been vehicles for the virus. Then those should be traced back the food chain. With luck, superimposing the trace-back routes of different cases infected by the same virus strain could, at some point, help identify the starting point of the contamination.

Although hepatitis A is not normally a deadly disease (for reasonably healthy adults), it can be a rather "unpleasant" experience. Thankfully, consumers can minimise the risk by boiling frozen berries for about one minute; this will destroy the virus if present on the berries. Simply rinsing the berries with tap water may not be enough; depending on the type of the berries, they may have a large total surface with lots of niches where water cannot really reach (not to mention that fruits tend to have a hydrophobic surface... which reminds me of an older - yet irrelevant - post).

Moral line of the story - if there needs to be one: Risk communication, i.e., telling consumers (and businesses) what the hazard, the risk and the reasonable mitigation measures are, preferably in plain language, can be very effective when everything else fails.

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