Molecular analysis of norovirus in specimens from children enrolled in a 1982-1986 study in Belém, Brazil: A community-based longitudinal study

Abstract

Fecal specimens were collected during a longitudinal, community-based study in the city of Belém, North Brazil, that was conducted over 3 years (October 1982 to March 1986), in which 20 children were included from birth to 3 years of age. A total of 229 fecal samples were screened by real time RT-PCR targeting the junction region (ORF 1/2) of the norovirus (NoV) genome. NoV-positive samples were subjected to PCR and sequencing of the viral polymerase (ORF1) and viral protein 1 (VP1) genes (ORF2). The junction region was also sequenced to assess for recombination when ORF1 and ORF2 genotyping results were dissimilar. Samples classified as GII.P4/GII.4 were further characterized by sequencing the P2 subdomain of the viral capsid to determine possible alterations. An overall positivity of 16.1% (37/229) was observed, including GI (16.2%-6/37) and GII (83.8%-31/37) genogroups. Cases of NoV reinfection in at least 2-month intervals were observed, and 12 children developed at least one case of asymptomatic NoV infection. In total, 48.6% (18/37) NoV-positive samples were subjected to nucleotide sequencing analysis targeting the following polymerase genes: GI.P3 (n = 1), GII.Pa (n = 1), GII.Pc (n = 1), GII.P4 (n = 5), GII.P6 (n = 5), GII.P7 (n = 3), GII.P12 (n = 1), and GII.P22 (n = 1). For the VP1 gene, characterization was performed in 14 (77.8%) samples: GI.3 (n = 1), GII.2 (n = 1), GII.4 (n = 4), GII.6 (n = 4), GII.7 (n = 1), GII.12 (n = 1), GII.14 (n = 1), and GII.23 (n = 1). Recombination events were confirmed in three cases (GII.P12/GII.2, GII.P7/GII.14, and GII.Pa/GII.12), and four samples genotyped as GII.P4/GII.4 were analyzed to identify variants. None had contemporary counterparts. Three children developed consecutive NoV infections by different genotypes. The present report documents the importance of NoV as a cause of childhood infection during a longitudinal study conducted more than 30 years ago.

Epidemiological and molecular investigation of norovirus and astrovirus infections in Rio Branco, Acre, Northern Brazil: A retrospective study

“…The overall NoV positivity observed in the present study (12.3%) was lower than that observed in other studies conducted in the Amazon Region, such as the study from 1982 to 2011 in Belém city (16.9%) 33 and that in Manaus city from 2010 to 2011 (35.2%). 16 This difference may be explained by the fact that the samples in this study were collected in UPAs and ambulatory care centers, not from hospitalized children, so the symptoms were normally mild.…”

“…40 Regarding NoV, there is evidence of short-term immunity after infection; however, some individuals remain susceptible to developing clinical symptoms, while others will not develop symptoms even after direct contact with the virus. 33 Consequently, the data obtained in the present study reinforce the presence of these viruses in asymptomatic patients, which facilitates the spread of infections, recombination events, and may even lead to outbreaks and epidemics.…”

Genotype diversity and molecular evolution of noroviruses: A 30-year (1982-2011) comprehensive study with children from Northern Brazil

“…Preliminary data on the epidemiological aspects of the symptomatic and asymptomatic groups in a subset of these samples were previously published [14]. …”

Norovirus transmission mediated by asymptomatic family members in households

“…The ratio of asymptomatic NV infections ranges from <1% to >30%, depending on the setting [5,12]. Asymptomatic NV infection occurs in all age groups, including children and infants [13][14][15][16][17][18][19][20][21]. A comprehensive analysis of the attack rates of NV during outbreaks suggested that asymptomatic infections occur in a proportion of the population [22].…”