Background: Human caliciviruses (HuCV) cause outbreaks of gastroenteritis, but their role in sporadic diarrhea in young children is not well-established.

Methods: Children (n = 2398) participating in a trial of oral rhesus-human reassortant rotavirus tetravalent (RRV-TV) vaccine were evaluated from 2 months to 2 years of age. Stool specimens from 1477 episodes of acute gastroenteritis (788 in a placebo and 689 in a RRV-TV vaccine recipient group) were tested for human calicivirus (HuCV) by reverse transcriptase-PCR with the use of broadly reactive primers, and positive results were confirmed by Southern hybridization with probes specific for main genetic clusters of Genogroups I and II of HuCV.

Results: HuCV were detected in 158 (20%) and 155 (22%) cases of gastroenteritis in the placebo and RRV-TV vaccine groups, respectively. According to hybridization results, 8% of HuCV were of Genogroup I and 92% were of Genogroup II. The peak season of HuCV gastroenteritis was from November to February. Of the 148 patients with pure HuCV infection in the placebo group, 89% had vomiting, 79% had watery diarrhea, 21% had fever, 28% needed oral rehydration and 1.4% were hospitalized. The diarrhea in HuCV gastroenteritis was much less severe than that in rotavirus gastroenteritis, but vomiting was equally severe. There was no effect of RRV-TV vaccine on the frequency or clinical severity of HuCV gastroenteritis.

Conclusion: HuCVs are second in frequency to rotaviruses as causative agents in acute gastroenteritis in young children in the community.