An analysis of Salmonella in Germany has revealed an overall decline but an increase in imported cases and unknown types of the pathogen.

German national surveillance data on salmonellosis from 2012 to 2023 were analyzed. A total of 160,782 cases of salmonellosis were reported in this timeframe, with seasonal peaks during the summer months. Incidence declined from 26 per 100,000 in 2012 to 13 per 100,000 in 2023. This equates to 20,836 cases in 2012 and 10,666 in 2023.

Scientists said the decrease in incidence might reflect a positive trend in public health efforts and food safety.

A study published in the journal BMC Infectious Diseases found the proportion of imported cases has increased since 2012, reaching a peak of 1,943 in 2023. The overall incidence was higher in males and children younger than age of 5. The most frequent serovars were Salmonella Enteritidis and Salmonella Typhimurium. From 2020 onward, there was a rise in the number of unknown serovars.

Impact of changing methods and travel
Scientists said the increase in unknown serovars from 30 percent in 2020 to 39 percent in 2023 might be because of a shift to PCR-based testing methods. A survey among diagnostic laboratories in Germany in 2024 revealed some of them had switched to culture-independent methods. Cultivation of isolates is essential for sequencing and implementation of genomic surveillance, enabling a better detection of outbreaks.

The dataset consists of all salmonellosis cases reported to the Robert Koch Institute according to the Protection against Infections Act (IfSG). 

Information on the country of exposure was available for 76 percent of cases, allowing the classification of imported infections. More than 20,000 cases were classed as imported. The proportion increased from 10 percent in 2012 to 26 percent in 2023. Females, particularly those aged 25 to 29, were the highest proportion of imported cases.

The top countries of exposure were Turkey, Egypt, Thailand and Spain. Turkey and Spain are among the most common destinations for people from Germany.

The number of cases with unknown serovars increased from 2,595 in 2020 to 4,199 in 2023. The most frequently identified serovars were Salmonella Enteritidis and Salmonella Typhimurium. Other important types included Salmonella Infantis, Derby, and Muenchen.

Overall, 20,172 patients were hospitalized, with the proportion remaining stable between 2017 and 2023.

“The decrease in the incidence of salmonellosis in Germany between 2012 and 2023 might reflect a positive trend in public health efforts and food safety. The increased proportion of imported cases highlights the higher importance of monitoring and addressing travel-related exposures,” said researchers.