IRVINE, CA -- Using a technique developed to track pathogens in sewage, a California Sea Grant funded researcher has shown that potentially harmful human viruses are contaminating coastal waters in Southern California at major river mouths.
Tests have not determined whether the viruses are virulent, but their presence does indicate that human waste is making its way into urban waterways. Because of the health risks associated with human waste, some groups are beginning to test their creeks and drainage culverts for signs of human contamination.
The risk of contamination from human waste appears to be significant, according to a survey of 12 river mouths in Los Angeles, Orange and San Diego counties conducted by assistant professor Sunny Jiang at UC Irvine. In the 1999 survey, also funded by California Sea Grant, Jiang reports that four of the 12 sites sampled tested positive for the presence of the human adenovirus: the Los Angeles, San Gabriel, Santa Ana and Tijuana river mouths. Of these four only the Los Angeles river mouth also registered as having high fecal bacteria levels, the standard criteria for evaluating water quality, closing beaches and monitoring compliance with federal clean water laws.
Because the presence of the virus did not correspond with high bacteria counts, Jiang said she believes the current water quality standards are "not adequately indicating human health risks."
"The presence of the virus does not correlate with high levels of bacteria," Jiang said. "Therefore, you don't have a beach closure and are potentially exposing people to health risks."
The adenovirus is considered a pathogen and is a member of a larger group of enteric viruses, which includes hepatitis A. When ingested, enteric viruses may attack the gastrointestinal track or the respiratory system, sometimes fatally. More typically, infection causes sore throat, diarrhea, fever and nausea. There are more than 100 viruses found in human waste that can survive for as long as 130 days in seawater. None of these are routinely tested by California health officials.
Ten years ago while a graduate student at University of South Florida, Jiang developed a technique for tracking viruses in human sewage. She used the method to show that raw sewage in septic tanks was leaking into coral reef ecosystems in the Florida Keys.
For the study in California, Jiang began tracking the adenovirus, which is a direct indicator of human viral contamination. The virus is also the only in its class that contains fragments of DNA instead of RNA, a characteristic that makes detection a little bit simpler.
Her findings and those of her colleagues are published in the January, 2001 issue of Applied and Environmental Microbiology.
Jiang notes that her virus-detection is unable, as yet, to determine whether adenoviruses are dead or alive. But she said, "even if one (type of virus) is dead maybe other harmful pathogens are alive."
The key advantage of testing for the adenovirus is that it definitively shows that human waste is contaminating waters, she said. Standard bacterial counts do not distinguish waste from animals and people. As a result, rivers that meander through wilderness may show misleadingly high bacterial counts while streams through suburban neighborhoods may contain dangerous human pathogens even though bacterial counts are normal. Distinguishing human and animal pathogens is crucial because it is human pathogens that generally pose the greatest health risk for people.
At present, Jiang's virus-detection system is somewhat unwieldy. To capture enough viruses to get an accurate portrait of water quality, Jiang must draw 20-liter water samples.
"Every thing we are doing is in the research stage, but in theory we think the adenovirus can be used as an indicator for human viral pollution. We need to reconsider our monitoring and coastal water standards."
Groups have begun to request viral testing to better identify the sources of chronic water pollution, even though such testing is not mandatory.
Jiang is currently working with the Public Facilities and Resources Department in Orange County to test chronically polluted waters in the Aliso Creek watershed. She is also working with other UC Irvine professors on a project to study the impact of the Santa Ana River on beach pollution in Huntington Beach. Jiang and colleagues hope to begin sampling offshore waters near a sewage outfall pipe to examine whether human waste could be the culprit of a recent spate of beach closures in Huntington Beach.
Materials provided by National Sea Grant College Program. Note: Content may be edited for style and length.
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