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[Relationship between ABO histo-blood group type and an outbreak of norovirus gastroenteritis among primary and junior high school students: results of questionnaire-based study].

Noroviruses are common causative agents of epidemic gastroenteritis in humans. Recent studies showed that human susceptibility to noroviruses was associated with ABO histo-blood group type. It was also observed that various degrees of susceptibility were exhibited by different norovirus strains. In January 2003, an outbreak of acute gastroenteritis including 661 affected primary and junior high school students occurred through lunch bread contaminated with norovirus in Hokkaido, Japan. To clarify the relationship between ABO histo-blood group type and the norovirus infection, we performed a written questionnaire to schoolchildren about the consumption of the bread, onset of symptoms and person-to-person transmission in their household. Questionnaires were returned from 722 schoolchildren (response rate, 65.8%), of whom 55.3% suffered gastroenteritis. As a result of this survey, it was found that schoolchildren with blood group type A (71.1%, 133/187) were more susceptible to the norovirus infection, whereas, schoolchildren with blood group type AB (55.3%, 26/47) were less affected (P (Z0) < 0.025). In addition, the presumptive prevalence rate of person-to-person transmission in each household indicated that schoolchildren with blood group type AB (19.2%, 5/26) had a lower risk of infection than those with blood group type A or O [A : 41.4%, 55/133 O : 39.5%, 49/124 (unknown for one case) ] [P (Z0) < 0.025]. Our findings suggested that persons with blood group type AB were less affected by the norovirus infection in this outbreak.