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Open Access Publications from the University of California

Is urban runoff a source of human pathogenic viruses to recreational beach waters?


The Aim of this study is to investigate human viral contamination in urban rivers and its impact on coastal waters of southern California. During the first year study, three types of human viruses (adeno, entero and hepatitis A) were detected using nested- and RT-PCR at eleven rivers and creeks along southern California coast. Fecal indicator bacteria as well as somatic and F-specific coliphage were also tested. Approximately 50% of the sites were positive for human adenoviruses. However, there was no clear relationship between detection of human viruses and the concentration of indicator bacteria and coliphage. Both fecal indicator bacteria and human viral input at beaches near river mouths were associated with storm events. The first storm of the wet season seemed to have the greatest impact on the coastal water quality than following storm events. During the second year of study, a detailed seasonal assessment of microbial pollution was conducted in two major Southern California urban rivers, San Gabriel and Los Angeles. A total of 114 river samples from five different sample locations along these two rivers were collected over a one-year period and analyzed for fecal indicator bacteria, including total coliform, fecal coliform, and enterococcus and indicator viruses, including F-specific and somatic coliphage, and human entero and adenoviruses. Based on the California recreational water quality standards, 52.5% of the samples exceeded at least one fecal indicator bacteria standard. Both somatic and F-specific coliphage were detected in higher concentrations (up to 5x102 PFU/100ml) during storm events. Enterovirus was detected in ~13% of the samples by reverse-transcription PCR. Adenovirus was detected by real-time PCR in approximately 50% of the samples, with concentrations ranging from 10 to >106 genomes per liter. However, plaque assay using two human tissue culture cell lines, HEK-293A and A549, yielded negative results suggesting adenoviruses detected by real-time PCR may not be infectious. Correlations between human adenoviruses and F-specific (p=0.13) and somatic coliphages (p=0.06) were found. However, these correlations were not statistically significant at 95% level. No significant correlation between human adenoviruses and fecal indicator bacteria (total coliform, fecal coliform, and enterococcus) was observed. This study presents the first quantitative measure of human adenoviruses in urban rivers and their statistical relationship to fecal indicator bacteria and coliphages. This study also provides the first direct evidence that human viruses are prevalent in southern California urban rivers.

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