Community acquired diarrhea--the incidence of Astrovirus infections in Germany

Astroviruses are increasingly recognized as a cause of human gastroenteritis. Electron microscopy (EM) has been considered the "gold standard" method for diagnosis, but this approach is limited to a few laboratories. We evaluated a commercial enzyme immunoassay (EIA) (IDEIA Astrovirus, DAKO Diagnostika, Hamburg, Germany) for the direct detection of antigen in fecal samples. In comparison to EM, the assay scored 100% in sensitivity and specificity (n = 213; 26 positive samples) and reacted with strains representing all known serotypes. Over an 11-month period 4,211 stool samples from unselected German patients suffering from acute gastroenteritis were examined. Etiologically responsible microorganisms were found in 13.0% of cases, with astrovirus the third most common pathogen (1.2%) behind Salmonella spp. (2.9%) and Rotavirus (2.5%), representing 13.5% of all positive specimens. Norwalk-like viruses (NLV), fungi, and protozoa were not tested. In infants of < 2 years of age (n = 458) the incidence of astrovirus infection was significantly higher (2.8%) compared to children of 2-7 years of age (n = 578; 1.7%) and those of > 7 years of age (n = 3,175; 0.9%). The frequency revealed a peak in winter (mean November-February: 2.0% versus other months: 0.8%).