Study Finds Human Viruses Contaminating Ocean Off California

MONITOR Wire Services

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, 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.

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."

Her findings and those of her colleagues were published in the January, 2001 issue of Applied and Environmental Microbiology.