Municipal Sewer & Water magazine recently interviewed Dr. Adrianus Vlugman, a featured speaker at this year’s Water & Wastewater Equipment, Treatment & Transport (WWETT) Show, which will be held Feb. 23-26 at the Indiana Convention Center in Indianapolis. Vlugman is a senior advisor on water, sanitation and environmental health at the World Health Organization, and on Feb. 26, he will speak about the transfer of communicable disease in water and wastewater. Here, he offers a glimpse into his upcoming presentation.

We’ll be posting a Q&A with Dr. Vlugman every day this week, so check back often.

MSW: Concern arose about Ebola in the U.S. after a few patients were treated here. Wastewater workers expressed concern about whether they could contract Ebola through exposure to sewage. What would you say to them about the seriousness of that risk?

Dr. Vlugman: Ebola viral disease is very contagious and is transmitted from human to human through direct contact with infected bodily fluids (e.g. blood, vomit, feces) of an Ebola patient to the mucous membranes or into the bloodstream (via wounds and cuts) of another noninfected person. Ebola is not airborne, foodborne or water borne.

Let’s apply the concept of risk to assess the threat of Ebola to operators at wastewater treatment plants:

West Africa now has more than 22,000 cases of Ebola, with a case fatality rate of 50 to 60 percent. This is already a significant reduction from the initial 90 percent fatality rate at the beginning of the outbreak in early 2014. Of the six cases of Ebola patients treated outside of West Africa, four in the United States and one each in Spain and the U.K., one person has died: a fatality rate of 17 percent.

The chance that a case represents itself here is also much lower due to exit screening in West Africa and improved procedures to protect health care workers. Also, the number of new cases is steadily decreasing. In the third week of January, fewer than 100 new cases were reported, while in September 2014 up to 850 new cases were reported per week. This reduction has been achieved by early detection and isolation of the patients along with better contact tracing.

The most likely scenario is that a health care worker returns to the U.S. and develops the symptoms here and will be treated in the hospital, where the diarrhea of that patient will be flushed and will reach a wastewater treatment plant. We know the virus is very fragile and weak, and once outside of a sick person, it will quickly die off in the sewer system. Furthermore, the concentration will be further reduced due to the enormous dilution occurring in the sewer system. We don’t know the exact die-off rate, and only this month the University of North Carolina started to study this issue in a project called: “RAPID: On Site Disinfection and Survival of Ebola and Other Viruses in Human Fecal Wastes and Sewage.”

There is no evidence to date that Ebola can be transmitted via exposure to sewage. But absence of evidence is no evidence of absence. The above-mentioned research will answer this question, but until then it is impossible to quantify the occupational risk of contracting Ebola from wastewater. Basic risk assessment strategies require prudency and to err on the side of caution. Assuming some viable viruses could arrive at the sewer plant, infection would only be possible through direct contact of the virus with mucous membranes and through cuts and wounds.

By practicing adequate personal hygiene and using PPE, following WHO and CDC guidelines when working with untreated sewage, wastewater workers will prevent exposure to not only Ebola but also other pathogens.

MSW: What is the risk of Ebola transmission through wastewater or drinking water? Is this a health threat? Please explain.

Dr. Vlugman: Ebola is not airborne, foodborne or water borne.

The effluent from wastewater treatment processes should be safe because U.S. plants are designed to inactivate and remove pathogens such as Ebola. The effluent from such plants can be safely discharged without risk to public health.

As a public health threat, the probability of being infected by Ebola through disposal of treated wastewater and drinking water is negligible.

As an occupational health threat to operators at wastewater treatment plants, the risk of exposure with Ebola through wastewater is very small, smaller than the risk to other diseases. Practicing appropriate personal hygiene and wearing adequate PPE will minimize risk to Ebola.

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Interested in hearing more from Dr. Vlugman? Then attend the WWETT Show from Feb. 23-26 at the Indiana Convention Center in Indianapolis. For more information on registration, speakers, education opportunities and more, visit www.wwettshow.com.