&EPA
United States
Environmental Protection
Agency
Office of Water
EPA823-F-16-001
July 2016
2016 Coliphage Experts Workshop:
Discussion Topics and Findings
Summary
EPA is developing Clean Water Act §304(a) Recreational Water Quality Criteria (RWQC) for coliphage, a viral
indicator, to ensure public health protection when recreating in water bodies that may be affected by human
fecal contamination. On March 1-2, 2016, EPA convened the Coliphage Experts Workshop to engage twelve
internationally recognized experts on the state of the science of coliphages and their usefulness as viral
indicators in recreational waters. Experts represented a spectrum of perspectives from academia, the
wastewater industry, and other federal agencies including the Centers for Disease Control and Prevention and
the Food and Drug Administration. Experts addressed charge questions related to five topic areas over the
course of the two-day meeting.
Background
Viruses cause the majority of illnesses associated with primary contact recreation in surface waters impacted
by human sources. While EPA recommends coliphage as an option for evaluating fecal contamination in
groundwater, the Agency does not currently have a recommended indicator of viruses in surface waters that is
protective of human health for primary contact recreation. Coliphages, viruses used to indicate the presence
of a health risk, are not themselves dangerous to human health. Coliphages are useful for evaluating surface
water quality because they exhibit numerous desirable indicator characteristics. For example, they:
• are of fecal origin and present in high numbers in sewage;
• are physically similar to viruses causing illnesses associated with primary contact recreation;
• do not re-grow in surface waters, thus their presence specifically indicates fecal contamination;
• are non-pathogenic;
• can be counted cheaply, easily, and quickly;
• show correlations to gastrointestinal illness; and
• are similarly resistant to sewage treatment and environmental insults as enteric viruses of concern.
Discussion Topics
• Topic 1: The Need for a Viral Indicator - Workshop participants were asked to comment on EPA's
conclusion that the literature (including epidemiological, risk assessment, outbreak, and microbiological)
indicates that viruses are an important cause of illnesses associated with exposure to ambient recreational
waters and that coliphages can be used as an indicator of fecal contamination. The participants also
identified the most important advantages and disadvantages of using coliphage for assessing fecal
contamination in surface waters compared to traditional fecal indicator bacteria (FIB).
• Topic 2: Coliphage as a Predictor of Gastrointestinal Illnesses - Workshop participants were asked to
comment on the overall strength of the association between coliphage and human health illness in
epidemiological studies conducted in ambient recreational waters, identify specific characteristics that
influence the association between coliphage and human health illness, and identify specific conditions
under which traditional FIB are not adequate to protect public health.
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• Topic 3: Coliphage as an Indicator of Wastewater Treatment Performance - Workshop participants were
asked to comment on EPA's conclusion that human pathogenic viruses are entering surface waters via
wastewater treatment effluent. Participants summarized the most important reasons coliphages are useful
models of the behavior of enteric viruses in wastewater treatment and disinfection processes.
• Topic 4: Male-specific versus Somatic Coliphage - The participants identified the most important
advantages and disadvantages of using these two types of coliphages as predictors of human health illness
in recreational waters and as indicators of wastewater treatment performance.
• Topic 5: Systematic Literature Review of Viral Densities - EPA has conducted systematic literature reviews
to understand and document densities of key viral pathogens (norviruses and adenoviruses) and
coliphages in raw wastewater. Participants reviewed the approach and information collected to date.
Workshop Findings
Topic 1: Need for a Viral Indicator
• Individual experts agreed that viruses are a source of illness in recreational water exposures.
• Viruses can enter surface waters via wastewater treatment plant (WWTP) effluent. Especially during wet
weather and when WWTPs exceed design flows.
• Coliphages are more similar to human pathogenic viruses than the traditional FIB and they mimic the
persistence of human pathogenic viruses.
• Coliphages have been shown to be useful in evaluating individual wastewater treatment processes,
disinfection efficacy, and shellfish harvesting waters.
• Currently available, inexpensive coliphage test methods could be developed into simple kits. Rapid,
commercial methods (results under eight hours) exist, which could be useful for swimming advisories at
beaches.
Topic 2: Predictor of Gastrointestinal Illness
• Future epidemiological studies should specifically include coliphages as measured indicators.
Topic 3: Indicator of WWTP performance
• Coliphages are consistently present in municipal sewage and provide a baseline for looking at different
WWTP processes under varied conditions. Experts indicated the literature suggests coliphage and human
viruses have more similar log-reductions during wastewater treatment, compared to traditional FIB.
Topic 4: Male-specific vs Somatic Coliphages
• Opinions ranged on whether somatic, male-specific coliphage, or both would be better for various
applications. There is evidence for both showing relationship to gastrointestinal illness. Male-specific
coliphage behave more similarly to RNA viruses under some conditions and are currently used successfully
by the Interstate Shellfish Sanitation Conference and Food and Drug Administration for shellfish waters.
Somatic coliphage may persist longer than male-specific coliphage and may be present in greater
concentrations in raw sewage. Laboratory bacterial hosts exist that can detect both coliphage types.
Topic 5: Review of Viral Densities
• Individual experts supported how the systematic analysis was structured and conducted.
Where can I find more information?
EPA plans to publish more detailed outcomes of the workshop in a peer-reviewed workshop proceedings
document in early 2017. For additional information on EPA's efforts to develop recreational water quality
criteria for coliphage, please visit EPA's water quality criteria website at: https://www.epa.gov/wqc/microbial-
pathogenrecreational-water-quality-criteria or email Sharon Nappier at nappier.sharon@epa.gov.
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