New study to shed light on persistence of Ebola virus in wastewater
In light of the outbreak of the Ebola virus in West Africa, new research by a group of microbial risk-assessment and virology researchers suggests that the procedures for disposal of Ebola-contaminated liquid waste might underestimate its ability to survive in wastewater.
PITTSBURGH, PA, Aug. 27, 2015 -- In light of the historic outbreak of the Ebola virus in West Africa that began in March 2014, which has killed more than 11,000 people since, new research conducted by a group of microbial risk-assessment and virology researchers suggests that the procedures for disposal of Ebola-contaminated liquid waste might underestimate the virus' ability to survive in wastewater.
Current epidemic response procedures from both the World Health Organization and the Centers for Disease Control and Prevention advise that after a period of days, Ebola-contaminated liquid can be disposed of directly into a sewage system without additional treatment. However, new data recently published by the University of Pittsburgh, Drexel University and the National Institutes of Health (NIH) indicate that Ebola can survive in detectable concentrations in wastewater for at least a week or longer.
"Initial research by the WHO and CDC recommended disposing of Ebola-contaminated liquid waste into a latrine or treatment system without disinfection because the virus wasn't expected to persist in wastewater," explained Kyle J. Bibby, assistant professor of civil and environmental engineering at Pitt's Swanson School of Engineering and principal investigator of the study "Persistence of Ebola Virus in Sterilized Wastewater. "However, we found that the virus persisted over a period of at least eight days."
The researchers gathered their data by observing the change in viral particle concentration in two samples, spiked with different concentrations of the virus, over an eight-day period. The testing was performed in a secured laboratory at the NIH. While the researchers observed a 99-percent decrease in concentration after the first day, the remaining viral particles were detectable for the duration of the experiment.
"These results demonstrate a greater persistence of Ebola virus in wastewater than previously speculated," said Charles Haas, co-author; head of the Department of Civil, Architectural, and Environmental Engineering; the LD Betz Professor of Environmental Engineering; and director of the Environmental Engineering Program. "While the Ebola virus was found to be generally less persistent than enteric viruses in wastewater, the identified survival period might suggest a potential of a wastewater exposure route."
The team also noted that the virus' seemingly early decay upon entry into wastewater might be due to the viral particles clumping together or latching onto other particles in the water, rather than the virus dying. These phenomena would actually make the viruses less susceptible to environmental factors, such as disinfectants, that would normally kill them off.
A proposed solution, already adopted by the WHO, would be to hold the contaminated liquid waste for a longer period of time before releasing it into the sewage system. Another might be to pretreat it with an antiviral agent, such as chlorine, although performance data on disinfectants is needed as well. These options would provide more time for the viral concentration to decay and for the remaining viruses to be inactivated.