Epidemiological profiles of norovirus genotypes in children with and without acute gastroenteritis from the northwestern Amazon region.

Noroviruses causes acute gastroenteritis (AGE) worldwide, with children living in low-income areas aged ≤5 years being the most vulnerable. Histo-blood group antigens (HBGA) are recognized as attachment factors for human noroviruses and susceptibility of a given genotype is frequently dependent on the secretor phenotype mediated by FUT2 genotype. This retrospective study involved 734 children aged ≤5 years with AGE (cases group; 66 %, 485/734) or non-AGE (control group; 34 %, 249/734), from the Amazon rainforest (Brazil, Venezuela, and Guyana) and in our previous studies, 87 % of children were positive secretors (641/734). A total of 40.2 % (88/219; GII) and 14.6 % (7/48; GI) of noroviruses were successfully genotyped, being: GII.1 (n = 5), GII.2 (n = 25), GII.4 (n = 32), GII.6 (n = 19), GII.7 (n = 5), GII.14 (n = 2), GI.2 (n = 1), GI.3 (n = 4) and GI.7 (n = 2). Most genotyped GII norovirus including all 32 GII.4, were detected in secretor-positive children (94.3 %, 83/88). Only genotypes GII.2 (n = 2), GII.6 (n = 3), GI.2 (n = 1) and GI.7 (n = 1) were detected in secretor-negative children. Of note, the predominant GII.4 and the GII.6 were not significantly associated with AGE (OR 1.1; 95 % CI 0.5 to 2.4, P = 0.7 and OR 1.4; 95 % CI 0.5 to 4.0, P = 0.4, respectively), in contrast to GII.2 was associated with AGE (OR 6.1; 95 % CI 1.4 to 26.2, P = 0.01). Genotypes GII.2, and GII.4 were detected in all age groups at high frequencies. In conclusion a great diversity of norovirus genotypes circulating in the Amazon region. Only the GII.2 genotype was associated with AGE, while the predominant GII.4 was detected at similar frequencies in both children with AGE and children without AGE.