Josephine van Dongen

Chapter 2 26 Abstract Background Infants with medical risk conditions are vulnerable to childhood infections including acute gastroenteritis (AGE).To guide prevention programs, we quantified AGE incidence, severity, and virus prevalence among medical risk infants in the Netherlands. Methods This prospective cohor t-study was par t of the RIVAR-project recruiting infants with prematurity, low bir th weight or severe congenital conditions in 13 hospitals. Follow up included 18 monthly health questionnaires detailing AGE symptoms and healthcare usage. Parents were also instructed to notify when an infant developed AGE, to collect a stool sample and complete a daily severity score (MVS). Stool samples were analyzed by realtime PCR for rota- noro-, adeno- and astrovirus. Results Between November 2014 and October 2017, 631 infants par ticipated during 9125 person- months of observation. In total 559 episodes were identified.The mean AGE IR was 73.5 per 100 person-years (PY) (95%CI: 67.6 - 79.9) and increased with age (IR: 48.3 (39.8-58.3) vs. 80.2 (73.0-88.1)/100PY for ages 1-5 vs. 6-18 months, respectively). Healthcare was attended for 38.1% (213/559) and 26.8% (68/254) were classified as severe based on the MVS. Stool samples were obtained from 254 AGE episodes. Norovirus was identified in 65 (25.6%) and rotavirus in 44 (17.7%). Adeno- and astrovirus together accounted for 8.3% (N=21). Severe AGE occurred most frequently in rotavirus positive episodes. Conclusion The observed AGE incidence, severity and healthcare usage among medical risk infants confirms substantial disease burden. Norovirus and rotavirus are the dominant pathogens and severe episodes occurred most frequently in children with rotavirus infection. AGE prevention in medical risk infants should be prioritized.