Natural history of human calicivirus infection: a prospective cohort study.

We investigated the natural history of human Calicivirus infection in the community. Clinical information was obtained from 99 subjects infected with Norwalk-like viruses (NLV) and 40 subjects infected with Sapporo-like viruses (SLV) in a prospective, community-based cohort study. NLV infection was common in all age groups, whereas SLV infection was mainly restricted to children aged <5 years. Symptoms lasted for a median of 5 and 6 days for NLV and SLV infections, respectively. Disease was characterized by diarrhea during the first 5 days (87% of patients with NLV infection and 95% of patients with SLV infection) and vomiting on the first day (74% for NLV and 60% for SLV). Vomiting was less common in children aged <1 year (59% for NLV and 44% for SLV) than it was among children aged >/=1 year (>75% for NLV and >67% for SLV). Overall, NLV was detected in 26% of patients up to 3 weeks after the onset of illness. This proportion was highest (38%) for children aged <1 year. SLV shedding subsided after 14 days. These data show that the durations of disease and viral shedding of caliciviruses are longer than has been described elsewhere. Therefore, the impact of these infections may have been underestimated.