Norovirus (NoV) is one of the most important aetiological agents of acute gastroenteritis both in developed and developing countries. NoV is shed in high concentrations by infected persons and contaminates recreational and drinking water through sewage discharge into the environment. The aim of this study was to determine the prevalence, genotypes and removal ratio of NoV by PCR, seminested-PCR and quantitative PCR (qPCR) assays in a sewage treatment plant in Rio de Janeiro city, Brazil, during one year of surveillance. NoV was detected in 7 (15%), 14 (29%) and 28 (58%) samples using PCR, seminested-PCR and qPCR, respectively. The mean removal ratio for the activated sludge process was 0.6 log10 for NoV genogroup I (GI) and 0.32 log10 for NoV genogroup II (GII). The peak NoV concentration was detected in the coldest months, with 53,300 genomic copies/litre. Nucleotide sequencing and phylogenetic analysis revealed that five strains clustered with GI strains and six with GII strains. This study demonstrates that NoV spreads into the environment despite the sewage treatment process and remains a source of waterborne outbreaks of acute gastroenteritis.

Norovirus (NoV) infections are a major cause of acute gastroenteritis outbreaks around the world. In Brazil, the surveillance system for acute diarrhoea does not include the diagnosis of NoV, precluding the ability to assess its impact on public health. The present study assessed the circulation of NoV genotypes in different Brazilian states by partial nucleotide sequencing analysis of the genomic region coding for the major capsid viral protein. NoV genogroup II genotype 4 (GII.4) was the prevalent (78%) followed by GII.6, GII.7, GII.12, GII.16 and GII.17, demonstrating the great diversity of NoV genotypes circulating in Brazil. Thus, this paper highlights the importance of a virological surveillance system to detect and characterize emerging strains of NoV and their spreading potential.

Sewage discharge is considered to be the main source of virus contamination in aquatic environments. There is no correlation between the presence of viruses and the presence of fecal coliforms in water; therefore virological markers are needed when monitoring contamination. This study investigates DNA and RNA virus concentrations in wastewater and evaluates a potential virus marker of human contamination. Influent and effluent samples were collected twice a month throughout a 1-year period. Viruses were detected using quantitative polymerase chain reaction protocols; nucleotide sequencing was carried out for virus genotyping. Human adenovirus (HAdV) and polyomavirus JC (JCPyV) were the most prevalent viruses found in influent samples (100%) with a virus load that ranged from 106 to 105 genome copies per liter (gc l–1). Norovirus genogroup II (NoV GII) and human astrovirus (HAstV) were less prevalent, and ranged from 104 to 103gc l–1. Quantitative data on virus profiles in wastewaters stress the high level of rotavirus species A environmental dissemination and address the potential of HAdV as a useful virological marker of virus contamination in aquatic environments. This study corroborates other studies performed in developed countries on DNA viruses as good markers of human fecal contamination.