Rotaviruses cause severe gastroenteritis in infants, in which the viruses interact with human histo-blood group antigens (HBGAs) as attachment and host susceptibility factors. While gastroenteritis outbreaks caused by rotaviruses are uncommon in adolescents, we reported here one that occurred in a middle school in China. Rectal swabs and saliva samples were collected from symptomatic and asymptomatic students, and samples were also collected from the environment. Using PCR, followed by DNA sequencing, a single G9P[8] rotavirus strain was identified as the causative agent. The attack rate of the outbreak was 13.5% for boarders, which was significantly higher than that of day students (1.8%). Person-to-person transmission was the most plausible transmission mode. The HBGA phenotypes of the individuals in the study were determined by enzyme immunoassay, using saliva samples, while recombinant VP8* protein of the causative rotavirus strain was produced for HBGA binding assays to evaluate the host susceptibility. Our data showed that secretor individuals had a significantly higher risk of infection than nonsecretors. Accordingly, the VP8* protein bound nearly all secretor saliva samples, but not those of nonsecretors, explaining the observed infection of secretor individuals only. This is the first single-outbreak-based investigation showing that P[8] rotavirus infected only secretors. Our investigation also suggests that health education of school students is an important countermeasure against an outbreak of communicable disease.