Foodborne hepatitis A infection is not uncommon in Europe, but is most often associated with travel to parts of the world where the disease is endemic and hygiene standards a little more lax than is desirable. But recently there have been a number of outbreaks that are unusual in that they involved people who seemed to have become infected without leaving home. One of these outbreaks has been going on since the beginning of last year and has so far made at least 1,315 people ill in eleven countries. Those figures are probably just the tip of the iceberg, since the hepatitis A virus often causes only very mild symptoms that may not require a visit to a doctor. This particular outbreak is thought to be linked to imported frozen berries, but despite extensive investigations all attempts to pinpoint the source have so far failed and new cases continue to be reported.
Now, information from Norway might provide new leads to help identify the origin of the outbreak. A number of hepatitis A infections caused by the same strain of the virus responsible for the larger outbreak have been linked to a specific food product for the first time. The culprit seems to be a frozen berry buttermilk cake imported from Germany. Armed with this information an international investigation is now in progress to track the berries used in the cake and find out where they were produced. If that can be done it might finally be possible to put an end to the wider outbreak.
One might ask why investigators have not been able to discover the source of the outbreak after more than a year. Part of the problem is that hepatitis A infections have a long incubation period – up to six weeks – before symptoms develop. That makes it hard for epidemiologists to establish a link with a specific food. Can you remember exactly what you ate six weeks ago? But the difficulty is compounded by the complexity of supply chains for certain food commodities. While frozen berries seem to be a prime suspect in this outbreak, tracking them back to their source has proven to be a major challenge. This is a perennial problem. I remember being shown a diagram of the distribution chain for lettuce involved in a Salmonella outbreak some years ago. It looked like a circuit diagram for a particularly complex bit of electronic equipment. No wonder it took months to unravel.
I suspect the contaminated berries will eventually turn out to have followed a similarly convoluted path, highlighting the growing need for better traceability in the food chain. The legal minimum of paper-based “one step forward, one step back” traceability is no longer adequate. Identifying the source of outbreaks, especially across international borders, relies on being able to track food products back to their place of origin. It’s time to take a more high-tech approach to traceability. Developments like cheap printable Radio Frequency Identification (RFID) tags would help to keep track of individual cases of foods during distribution much more effectively than paper labels and new cloud-based traceability software allows suppliers and customers to share information about specific shipments more easily. Tracing foods back to their origin shouldn’t need the detective skills of a Sherlock Holmes to accomplish.