Novel and classical human astroviruses in stool and cerebrospinal fluid: comprehensive screening in a tertiary care hospital, Switzerland

Classical human astroviruses (HAstV) are the third most common cause of non-bacterial acute gastroenteritis. Due to the lack of routine molecular assays, novel HAstV are underdiagnosed and the magnitude of their contribution to clinical disease remains unknown. To better understand their prevalence and the susceptible patient profile, we conducted a comprehensive screening of novel and classical HAstV in stool and cerebrospinal fluid (CSF) samples collected for clinical care in a tertiary care hospital using a specially designed rRT-PCR panel for the detection of novel (MLB1-3 and VA1-4) and classical HAstV. Of the 654 stool samples, 20 were positive for HAstV, and the novel (n=10; 3 MLB1, 4 MLB2; 3 VA2) and classical (n=10) serotypes were equally prevalent. None of the 105 CSF samples were positive. Investigating the patient profile, we found a higher prevalence (P=0.0002) of both novel and classical HAstV in pediatric stool samples (3.4% and 3%, respectively) compared with adult stool samples (0.5% and 0.7%, respectively). Furthermore, all novel and classical HAstV-positive pediatric subjects were ≤four years old, demonstrating similar susceptible populations. Forty-five percent of positive patients were immunocompromised (novel: 40%, classical: 50%). A comparison of novel and classical HAstV-positive cases showed a lower viral load for novel HAstV (P=0.0007) with significantly more upper respiratory symptoms (70% of subjects; P=0.02); this observation may suggest a unique pathogenic pathway. This study confirms the clinical and epidemiological relevance of novel HAstV and identifies a target population in which routine screening may yield clinically valuable information.