Real-time PCR quantification of human adenoviruses in urban rivers indicates genome prevalence but low infectivity

Quantitative detection of hepatitis a virus and enteroviruses near the United States-Mexico border and correlation with levels of fecal indicator bacteria

For decades, untreated sewage flowing northward from Tijuana, Mexico, via the Tijuana River has adversely affected the water quality of the recreational beaches of San Diego, California. We used quantitative reverse transcription-PCR to measure the levels of hepatitis A virus (HAV) and enteroviruses in coastal waters near the United States-Mexico border and compared these levels to those of the conventional fecal indicators, Escherichia coli and enterococci. Over a 2-year period from 2003 to 2005, a total of 20 samples were assayed at two sites during both wet and dry weather: the surfzone at the mouth of the Tijuana River and the surfzone near the pier at Imperial Beach (IB), California (about 2 km north of the mouth of the Tijuana River). HAV and enterovirus were detected in 79 and 93% of the wet-weather samples, respectively. HAV concentrations in these samples ranged from 105 to 30,771 viral particles/liter, and enterovirus levels ranged from 7 to 4,417 viral particles/liter. The concentrations of HAV and enterovirus were below the limit of detection for all dry weather samples collected at IB. Regression analyses showed a significant correlation between the densities of both fecal bacterial indicators and the levels of HAV (R2>0.61, P<0.0001) and enterovirus (R2>0.70, P<0.0001), a finding that supports the use of conventional bacterial indicators to predict the levels of these viruses in recreational marine waters.

Regional public health cost estimates of contaminated coastal waters: a case study of gastroenteritis at southern California beaches

We present estimates of annual public health impacts, both illnesses and cost of illness, attributable to excess gastrointestinal illnesses caused by swimming in contaminated coastal waters at beaches in southern California. Beach-specific enterococci densities are used as inputs to two epidemiological dose-response models to predict the risk of gastrointestinal illness at 28 beaches spanning 160 km of coastline in Los Angeles and Orange Counties. We use attendance data along with the health cost of gastrointestinal illness to estimate the number of illnesses among swimmers and their likely economic impact. We estimate that between 627,800 and 1,479,200 excess gastrointestinal illnesses occur at beaches in Los Angeles and Orange Counties each year. Using a conservative health cost of gastroenteritis, this corresponds to an annual economic loss of dollars 21 or dollars 51 million depending upon the underlying epidemiological model used (in year 2000 dollars). Results demonstrate that improving coastal water quality could result in a reduction of gastrointestinal illnesses locally and a concurrent savings in expenditures on related health care costs.