The Norwegian Food Safety Authority commissioned VKM to make the risk ranking report. It will be used for risk-based prioritisation of programmes for monitoring and controlling pathogens in food and water.

Twenty selected pathogens

The 20 pathogens had been selected by the Norwegian Food Safety Authority. VKM performed a multicriteria-based ranking of the pathogens in terms of their public health impact from food/water-borne transmission in Norway. The criteria, based on the incidence of food and waterborne disease that can be attributed to each pathogen, were:

the severity of acute and chronic disease

the proportion of those infected who become chronically ill

mortality and the probability of future increased burden of disease

The six highest-ranked infectious agents were, (in descending order): Toxoplasma gondii, Campylobacter spp., Echinococcus multilocularis, enterohaemorrhagic E. coli (EHEC), Listeria monocytogenes, and non-typhoid Salmonella.

"There was a significant overlap between the scores," says Taran Skjerdal, scientific leader for the team.

Identification of food sources

The identification of food sources was to reveal, among other things:

which foods the substances are regularly detected

the importance of food as a source of infection

what risk factors can be prevented

VKM examined data from national surveillance and monitoring programmes, prevalence surveys, outbreak investigations, and research, including epidemiological studies. When Norwegian data were sparse or absent, international reports and research were used.

"There was great variation with regard to which foods were the source of each pathogen," Skjerdal notes. She points out that fresh vegetables were identified as one of the most important food sources for 12 of the 20 infectious substances, drinking water was associated with eight, and five were associated with raw milk or products of raw milk.

Conclusions can change over time

“The results may change over time as new data become available from monitoring and research on pathogens and the diseases they cause. The systematic and transparent process described in this report will probably be most useful if it is repeated and updated regularly with new information," explains Skjerdal.

VKM's Panel on Biological Hazards has approved the report.