Campylobacter, Salmonella, and norovirus caused the highest burden of disease in Denmark in 2019, according to a study.

Researchers ranked seven foodborne pathogens for their health and economic impact on Danish society in 2019. Work covered Campylobacter, Salmonella, Shiga toxin-producing E. coli (STEC), Yersinia enterocolitica, Listeria monocytogenes, norovirus and hepatitis A.

The team looked at incidence, mortality, disability-adjusted life years (DALY), and economic burden in terms of direct and indirect health costs. 

These seven pathogens accounted for 268,372 infections, 98 deaths, and 3,121 DALYs. They led to an expenditure of €434 million ($444 million) in one year in the country, which has 5.8 million people, according to the study published in the journal Foodborne Pathogens and Disease.

Hepatitis A at the bottom
Six of the seven are reportable in Denmark, meaning laboratory confirmed cases must be reported to Statens Serum Institute. The reporting system for norovirus only captures outbreak-related cases, which represent a small fraction of the total so researchers used other methods.

Results show there may be differences in the ranking of foodborne pathogens, depending on the metrics used. The order for burden of disease was affected depending on whether all cases were included or only those estimated to be foodborne.

Infections by Campylobacter, Salmonella, and norovirus caused the most DALYs. Norovirus caused the higher number of cases, and Campylobacter the most deaths. Hepatitis A had the lowest burden.

In 2019, Campylobacter was predicted to have caused nearly 59,000 cases and 41 premature deaths while norovirus was behind 185,000 cases and 27 deaths. Listeriosis has a low degree of underreporting and relatively high costs per case.

Cost of illness
Campylobacter, norovirus and STEC had the biggest costs. The highest total health costs were estimated for norovirus at €185 million ($189 million), Campylobacter at €124 million ($127 million), followed by STEC at €46 million ($47 million) and Listeria monocytogenes at €43 million ($44 million). The costs of Salmonella were estimated to be €30 million ($30.7 million), €5 million ($5.1 million) for Yersinia and €1 million for hepatitis A.

The pathogen leading to the highest direct health costs was STEC at €7.8 million ($8 million). This was because of the on-average higher severity and need for medical treatment associated with severe infections. Costs of complicated hospitalized cases were more than 100 times larger than for mild cases. Next was Campylobacter at €1.8 million ($1.85 million).

Costs associated with complicated hospitalization cases of Campylobacter, Salmonella, and Yersinia enterocolitica were about 10-fold higher than for mild infections.

There was a clear age related pattern for all pathogens. The average cost per registered case for people older than 65 was substantially higher than in younger groups, mainly because of a relatively large mortality at older ages.

There was also an increasing share of more severe cases with higher risk of hospitalization and longer absenteeism from work with age. The age pattern for STEC was different because of an apparently higher share of complicated or fatal cases in the 5- to 14-year-old category.

Researchers said a combination of disease burden and cost of illness estimates was useful to guide policy decisions, preventive measures and to establish food safety priorities at the national level.

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