## 4 Discussion
assays is the inability to differentiate between infectious and non-infectious virus (i.e., to determine transmissibility); thus the communicable period of norovirus is unclear, and this has major implications for infection prevention and control practices. [PERSON] et al. reported that a RT-qPCR cycle threshold (Ct) cut-off of 30 might define the lower limit of transmissibility, based on experiments conducted with human intestinal enteroid cultures inoculated with GII.4 Sydney[P31]-infected fecal samples [31]. However, due to the lower sensitivity of viral culture systems for norovirus, the variable replication efficiencies of different norovirus genotypes in the enteroid system, and inter-laboratory variation in RT-qPCR assays, it is possible that norovirus in stool samples with a Ct value >30 might still be transmissible. The median rotavirus viral load of 12.3 log GE copies/g stool detected on Day 0 in our study aligns with a previous report [32]. We also found that compared to norovirus, rotavirus had a higher viral load on Day 0, but lower viral loads on Days 5 and 28. Moreover, we found that 52% of children tested positive for rotavirus on Day 28, which was lower than the 70% detection rate of norovirus on Day 28. However, prolonged rotavirus shedding of up to 57 days after symptom resolution has been reported [33; 34]. Although the ability to culture rotavirus was established in the 1980s [35], no studies examining the infectivity of rotavirus in stools had been undertaken to define the period of transmissibility. Few studies have reported the kinetics of viral load and shedding of adenovirus in stool samples [36; 37], especially for comparison with other gastroenteritis viruses. The available literature reports that adenovirus 40/41 had higher viral loads compared to non-enteric adenovirus in children with AGE [36]. We report a high viral load of adenovirus on Day 0, with a rapid decline in virus level on Days 5 and 28. Compared to norovirus and rotavirus, adenovirus had the lowest detection rate on Day 28 (13.6%), indicating that the duration of adenovirus 40/41 shedding in stool is shorter than norovirus and rotavirus. Although previous studies reported that a higher stool viral load was associated with severe clinical symptoms for norovirus infection in cancer patients at the time of diagnosis [38], we did not identify a significant correlation between norovirus viral load and disease severity on Day 0. A moderate correlation between adenovirus viral load and MVS score was observed in this study, which was in agreement with a previous finding that children infected with adenovirus with higher viral loads had more severe disease [37]. For rotavirus, it was reported that a higher level of fecal viral load was positively associated with disease severity in children [34]. We also identified a low correlation between the Day 0 rotavirus viral load and MVS score. As MVS scores were not available for Days 5 and 28 in this study, it was not clear whether there was an association between viral load and disease severity on those days. Some limitations merit mention. We did not sample specimens between Day 5 and Day 28; therefore, the kinetic of viral load and shedding during this time period was not clear. In addition, this study enrolled a cohort of otherwise healthy young children [18]; thus, the findings could not be extrapolated to the kinetics of virus shedding among immunocompromised children and those > 48 months of age.