[Epidemiological aspects of gastrointestinal infections]

The aim of this study was to investigate seasonal patterns and age-associated trends of the main bacterial, viral, and parasitic enteric pathogens in Southwest Germany.

From January 2002 through December 2008 a total of 99,057 patients were tested for Norovirus, Rotavirus, bacterial pathogens, Cryptosporidium parvum (C. parvum), and Giardia lamblia (G. lamblia).

All these pathogens were detected throughout the whole year. But there were distinctive seasonal patterns of activity of the following pathogens being detected: norovirus was detected mainly from September through April. The highest rotovirus activity was observed from December through June. But bacterial pathogens und C. parvum were found mainly from June to November. The percentage of positive results during the months with the highest activity was 10 - 49% for norovirus, 25% - 41% for rotavirus, 14 - 18% for bacterial infection and 3 - 4 % for C. parvum. G. lamblia and adenovirus were found throughout the year in 7 - 15% and 3 - 10% of samples, respectively. Moreover, the detection rate of different pathogens depended on patient age. In infants younger than one year, rotavirus, norovirus and adenovirus were most frequently isolated pathogenes. Stool samples from kindergarden- and school-age children were positive largely for bacterial pathogens such as Salmonella and Campylobacter particularly in late summer or early autum. In patients older than 60 years, norovirus, rotavirus, and toxin producing Clostridium difficile strains were the most common pathogens.

In view of the age and season related frequency of detection of enteric pathogens, a step-by-step diagnosis of gastrointestinal tract infections is recommended. Considering that most pathogens are detected sporadically over the whole year, the analysis of negative samples should be appropriately expanded. The knowledge of seasonal occurrence can also be applied to improve the application of hygienic measures.