Norovirus in feces and nasopharyngeal swab of children with and without acute gastroenteritis symptoms: First report of GI.5 in Brazil and GI.3 in nasopharyngeal swab

- This is the first investigation of norovirus in fecal and nasopharyngeal swab samples obtained from the same children.
- We report positivity rates in nasopharyngeal swabs of 11.4% from symptomatic and in 6.5% from asymptomatic children.
- A considerable genomic variability was found and a higher frequency of GII NoV was detected in fecal samples.
- This is the first report of GI.3 in nasopharyngeal swab samples and also the first report of GI.5 NoV in Brazil.
- Findings amplify the need to investigate NoV in respiratory tract of children with and without gastroenteritis.

BackgroundNoroviruses (NoVs) are an important cause of acute gastroenteritis (AGE), worldwide.ObjectivesTo evaluate the frequency, viral load and molecular profile of NoV in fecal and nasopharyngeal swab samples from hospitalized children, and to determine children's secretor status.Study designFrom May 2014 to May 2015, 219 children were included in the study, 96 with gastroenteric symptoms and 123 without gastroenteric symptoms. All fecal and nasopharyngeal swab samples were screened by TaqMan RT-qPCR duplex (GI/GII NoV) and quality samples were characterized by genomic sequencing.ResultsNorovirus positivity rate in feces was 15.4% in asymptomatic and 18.8% in the symptomatic group. The median viral loads in feces were 2.69 × 108 GC/g and 4.32 × 107 GC/g from children with or without AGE symptoms, respectively. In nasopharyngeal swab samples, the NoV positivity was 11.4% in symptomatic children, with a median viral load of 2.20 × 107 GC/mL and 6.5% in asymptomatic children, with an average viral load of 1.73 × 106 GC/mL. In only two cases NoV was detected in both samples. A considerable genomic variability was observed in feces, with six genotypes being detected, as follows: GII.4, GII.6, GI.3 and GII.3, GI.2 and GI.5. Two GI.3 was detected in nasopharyngeal swab.ConclusionsOur data reveal considerable NoV frequencies in both nasopharyngeal and fecal samples from symptomatic and asymptomatic children. Higher viral loads were detected in samples from AGE symptomatic children, when compared to asymptomatic children. High genomic variability was observed, with this being the first report of GI.5 NoV in Brazil and of GI.3 in nasopharyngeal swab samples.