Prevalence and genetic diversity of waterborne pathogenic viruses in surface waters of tropical urban catchments.

AIMS: To study the virological quality of surface water from highly urbanized tropical water catchment areas and to determine predominant enteric viral genotypes in surface water. METHODS AND RESULTS: A wide range of human pathogenic viruses in urban surface waters was screened by nested PCR assays after concentration by ultrafiltration. Among the 84 water samples collected, at least one virus was detected in 70 (83·3%) of these samples. Noroviruses were determined to be the most prevalent enteric viruses detected in urban surface water samples, followed by astroviruses, enteroviruses, adenoviruses and hepatitis A viruses. The molecular characterization of environmental viral isolates suggested co-circulation of multiple genotypes of both noroviruses GI and GII, astroviruses and enteroviruses in urban surface waters. CONCLUSIONS: Human enteric viruses with great genetic diversity were detected in surface waters, indicating the presence of human origin of faecal contamination in highly urbanized water catchment areas.

Environmental surveillance and molecular characterization of human enteric viruses in tropical urban wastewaters.

AIMS: To study the prevalence and genotypes of waterborne pathogenic viruses in urban wastewaters in the tropical region. METHODS AND RESULTS: Viruses in wastewaters collected at three water reclamation plants in Singapore were studied by molecular methods. Over a 6-month sampling period, adenoviruses, astroviruses and both norovirus genogroups I (GI) and II (GII) were detected in 100% of the sewage and secondary effluent. Enteroviruses and hepatitis A viruses (HAV) were found in 94 and 78% of sewage, and 89 and 28% of secondary effluent, respectively. By using quantitative real-time PCR, estimated concentrations of astrovirus in the sewage were 1-2 orders of magnitude higher than those for adenovirus, noroviruses GI and GII. Genotyping of environmental isolates revealed multiple genotypes of GI and GII noroviruses. Coxsackieviruses A, astrovirus type 1 and adenovirus type 41 were prevalent. Norovirus GII/4 and coxsackievirus A24 isolates in wastewaters were closely related to respective outbreak strains isolated previously in Singapore. CONCLUSIONS: This study showed the widespread occurrence of all tested enteric virus groups in urban wastewaters. Genetic diversity of astroviruses, enteroviruses and noroviruses in the tropical region was observed. SIGNIFICANCE AND IMPACT OF THE STUDY: The high prevalence and great genetic diversity of human enteric viruses in urban wastewaters strongly supports the need of further comprehensive studies for evaluating the public health risk associated with viral pathogens in water environments.