title: Asymptomatic norovirus infections in Nicaraguan children and its association with viral properties and histo-blood group antigens.
abstract: BACKGROUND
  It has been previously reported that histo-blood group antigens (HBGAs) and particularly secretor status provides protection against symptomatic norovirus infection, but it remains unclear to what extent this includes asymptomatic infections in children.
  
  
  METHODS
  To explore whether HBGAs or certain viral genotypes are associated with asymptomatic norovirus infections in a pediatric population in Nicaragua, we investigated 163 children ≤5 years of age, without a recent history of diarrhea (≤10 days).
  
  
  RESULTS
  Asymptomatic norovirus infections were observed in 11.7% (19/163), with children ≤6 months of age being most frequently infected (16%). Of the 19 norovirus-positive children, 4 (21%) and 10 (53%) were infected with genogroups GI and GII, respectively, and 4 children (21%) were infected with viruses of both genogroups. Most children had ≥10 viral genomes per gram of feces. Nucleotide sequence analysis (15/19) revealed uncommon genotypes, such as, GII.7 (n = 5) and GII.2 (n = 3). An interesting observation was the low frequency of norovirus GII.4 strains among the asymptomatic children. AB blood type, Lewis a (Le) phenotype and nonsecretor genotype (sese) were not found among the asymptomatic children, but they occurred in population controls.
  
  
  CONCLUSIONS
  Frequency of asymptomatic norovirus infections was similar to that observed in symptomatic children from Nicaragua. Norovirus GII.2 and GII.7 were frequently detected but the globally dominating GII.4 was infrequent. Host genetic factors previously observed to be associated with protection against symptomatic norovirus infection were not found in this study.
authors.affiliation: Department of Microbiology, University of León, UNAN-León, Nicaragua.
authors.forename: Filemon
authors.initials: F
authors.lastname: Bucardo
authors.forename: Johan
authors.initials: J
authors.lastname: Nordgren
authors.forename: Beatrice
authors.initials: B
authors.lastname: Carlsson
authors.forename: Elin
authors.initials: E
authors.lastname: Kindberg
authors.forename: Margarita
authors.initials: M
authors.lastname: Paniagua
authors.forename: Roland
authors.initials: R
authors.lastname: Möllby
authors.forename: Lennart
authors.initials: L
authors.lastname: Svensson
mesh_terms: D058345:Asymptomatic Infections / Q000453:epidemiology*; D001789:Blood Group Antigens / Q000032:analysis*; D017250:Caliciviridae Infections / Q000453:epidemiology* / Q000821:virology*; D002675:Child, Preschool; D005243:Feces / Q000821:virology; D005260:Female; D005838:Genotype; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D009527:Nicaragua; D029322:Norovirus / Q000145:classification* / Q000235:genetics* / Q000302:isolation & purification / Q000472:pathogenicity; D015995:Prevalence
chemical_list: D001789:Blood Group Antigens