Prolonged norovirus shedding in infants <= 6 months of age with gastroenteritis

Background: Noroviruses (NV) are one of the leading causes of gastroenteritis in young children; however, the duration of NV shedding in young children is not well known. Methods: Fecal specimens were collected from children with acute gastroenteritis at a pediatric clinic during the period from November to December 2002 and tested for NV by reverse transcription-polymerase chain reaction. Results: Of 71 children infected with NV, 60 (84.5%) were less than 3 years old. Among children aged < 2 years and those aged 2 to 5 years, the duration of illness was longer (7 days versus 3.5 days, P = 0.0069), the maximum number of stools in a 24-hour period was greater (7 versus 3, P = 0.0078) and a 20-point severity score was higher (11 versus 8, P = 0.0031) in patients aged < 2 years than in patients aged 2 to 5 years. Among the 23 children whose follow-up specimens were obtained, the median duration of NV shedding was 16 days (range, 5-47 days). Virus shedding for more than 2 weeks after onset was observed in 75% (6 of 8), 71.4% (5 of 7) and 25% (2 of 8) of children aged < 1 year, 1 year and 2 to 3 years, respectively. Three infants aged :56 months continued to excrete NV for an extremely long period (more than 42, 44 and 47 days from onset) after recovery. Conclusion: Long-term virus shedding after the disappearance of clinical symptoms was observed. Caution should be exercised when handling the excrement of infants and young children infected with NV.