SEA GRANT STUDY SAYS IT'S TIME TO TEST WATER FOR MORE THAN JUST BACTERIA
In America and most other countries of the world, the microbiological safety of beaches is determined by testing for the presence of fecal bacteria. Water found to be clear of bacteria is assumed to be safe.
However, a USC Sea Grant study indicates that standard might be misleading because human pathogenic viruses sometimes lurk in bacteria-free water.
"Our results suggest that
we should consider performing limited virus testing in recreational
waters in the near future, particularly at storm drains adjacent
to high-use beaches," said Jed Fuhrman, USC Sea Grant research
scientist and holder of the McCulloch-Crosby Chair in Marine
Biology. "Viruses are very different from bacteria. While
they may come from the same sewage contamination source as bacteria,
their subsequent fate in water can be dramatically different."
"We found the expected widespread distribution of viruses after heavy rains, but we often found viruses in storm drains, even during the summer dry weather," said Noble. The viruses detected were usually in the human enteric virus family, which includes poliovirus, echo-virus and Coxsackie virus. Hepatitis A virus has also been detected.
An extensive epidemiology study in Santa Monica Bay in 1995 showed significant risks associated with swimming near flowing storm drains. The study found that the incidence of illnesses such as rashes, GI disorders, and upper respiratory infections approximately doubled among those swimming at the mouth of a storm drain.
"Viruses probably cause a significant fraction of illnesses associated with sewage-contaminated water," Fuhrman said. "Our results confirm that it is a wise precaution to avoid swimming near storm drains year round, and even far from the drains after heavy rains."
Fuhrman and Noble analyzed water samples from beaches ranging from the Mexico border to Santa Barbara using a state-of-the-art molecular biology test called the Reverse-Transcriptase Polymerase Chain Reaction (RT-PCR), which detects the RNA genetic material of some groups of human pathogenic viruses. The test is a hundred times more sensitive and 10 times faster than virus-culturing methods.
"This is potentially a very good tool for testing beaches because it is fast and would allow decisions to be made quickly," said Fuhrman. But he added that RT-PCR is so sensitive that it can detect viral genes from inactive viruses, or the presence of viruses at levels so low they do not pose a threat to human health. "It is a valuable indicator to show how viral measurements relate to conventional bacterial indicators."
Noble will discuss her research on Tuesday, July 27 at a special panel on "Bacterial and Viral Contamination in the Coastal Zone" at 10:50 a.m. Noble will discuss Fuhrman and her research again on Wednesday, July 27 at 2 p.m. as part of an overall panel presenting the latest results of a major regional monitoring project looking at water quality issues in the Southern California Bight.
For more about the USC Sea Grant study visit the Sea Grant Media Center Web site's "Press Briefings" section. There one can hear an audio presentation by Fuhrman and Noble given earlier this year as part of an overall Sea Grant media briefing on the topic of marine environmental health linkages to human health. The Web site can be found at: http://www.seagrantnews.org/press/briefings.html
Sea Grant is a network of 29 university-based programs involving more than 300 institutions nationwide in research, education and the transfer of technology regarding coastal, marine and Great Lake issues. Sea Grant is supported by the U.S. Department of Commerce's National Oceanic and Atmospheric Administration (NOAA) in partnership with the states and private industry.