Viral load and genotypes of noroviruses in symptomatic and asymptomatic children in Southeastern Brazil
Received 17 April 2009; received in revised form 30 October 2009; accepted 11 November 2009. published online 09 December 2009.
Abstract
Background
Noroviruses (NoVs) are a major etiological agent of sporadic acute gastroenteritis worldwide.
Objectives
To detect, quantify and characterize genogroups and genotypes of NoVs in children with and without gastrointestinal symptoms.
Study design
NoVs were investigated by RT-PCR in a total of 319 fecal specimens from children up to three years old with (n=229) and without (n=90) acute diarrhea, between February 2003 and June 2004 in the emergency room in Vitória, Southeastern Brazil. NoVs were quantified by real-time PCR and genotyped.
Results
NoVs were detected in 17% (40/229) and 13% (12/90) of symptomatic and asymptomatic children, respectively. Six NoV-rotavirus A mixed infections were observed. Fifty-one strains were characterized as NoV GII and one as GI. Twenty strains were characterized as GII/4 (9/13), GII/3 (1/13), GII/6 (2/13) and GII/14 (1/13) in symptomatic and GII/3 (6/7) and GII/8 (1/7) in asymptomatic children. The median RNA viral loads were 8.39 and 7.15log10copies/g of fecal specimens for symptomatic and asymptomatic children, respectively (p=0.011). NoV load was lower when it was present in a mixed infection with rotavirus A (p=0.0005).
Conclusions
This study demonstrates a diversity of NoV strains circulating in this geographic area, and reports GII/8 and GII/14 in the American Continent for the first time. In addition, it confirms GII/4 as the most prevalent genotype in symptomatic children and identified GII/3 in an important frequency, especially in asymptomatic children. Furthermore, preliminary results show that symptomatic patients present a viral load that is significantly greater than asymptomatic children (p=0.011).
aNúcleo de Doenças Infecciosas, Health Science Center, Federal University of Espírito Santo, Av. Marechal Campos 1468, 29043-900 Maruipe, Vitória, ES, Brazil
bLaboratory of Comparative and Environmental Virology, Oswaldo Cruz Institute, Av. Brasil 4365, 21040-360 Rio de Janeiro, RJ, Brazil
cPediatric Department, Health Science Center, Federal University of Espírito Santo, Av. Marechal Campos 1468, 29043-900 Maruipe, Vitória, ES, Brazil
dPathology Department, Health Science Center, Federal University of Espírito Santo, Av. Marechal Campos 1468, 29043-900 Maruipe, Vitória, ES, Brazil
Corresponding author at: Lab. Gastroenterite Infecciosa, Depto Patologia, Núcleo de Doenças Infecciosas, CCS, Universidade Federal Espírito Santo, Av Marechal Campos 1468, 29043-900 Maruípe, Vitória, ES, Brazil. Tel.: +55 27 33357297; fax: +55 27 21227210.
ABSTRACT