New research finds that Ebola can survive in detectable concentrations in wastewater for 8 days – a finding that has implications for the disposal of contaminated liquid waste during epidemics and outbreaks.
The study, by researchers at the University of Pittsburgh, Drexel University – both in Philadelphia – and the National Institutes of Health (NIH), is published in Environmental Science & Technology Letters.
The current Ebola outbreak in West Africa is by far the worst since the disease first appeared in 1976. According to the latest World Health Organization (WHO) situation report, there have been 28,005 confirmed cases and 11,287 deaths to the virus since cases were first reported in March 2014.
In their background information, the authors note that in the wake of the outbreak, there remain significant questions on the appropriate handling of virus-contaminated liquid waste. One of these concerns is the persistence of Ebola in wastewater.
Studies have indicated that the virus can persist in survivors. For example, one study describes how viable Ebola virus was found in the eye of a survivor months after recovery.
In contrast, there is limited data on the fate and transport of Ebola in wastewater collection systems. Handling procedures from WHO and the Centers for Disease Control and Prevention (CDC) say Ebola-contaminated waste can be disposed of directly into the sewage system without additional treatment after a few days.
However, the new study, conducted under secured NIH lab conditions, by microbial risk assessment and virology researchers, suggests these procedures might underestimate Ebola’s ability to persist in wastewater, as study leader Kyle J. Bibby, assistant professor of civil and environmental engineering at Pittsburgh, explains:
“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. However, we found that the virus persisted over a period of at least 8 days.”
Over the 8 days of their study, Prof. Bibby and colleagues measured changes in viral particle concentration in two samples contaminated with different concentrations of the virus.
Although the concentration dropped by 99% over the first day, they could still detect virus particles over the remaining 7 days.
This shows Ebola virus persists far longer in wastewater than previously thought. Although the virus was found to be less persistent than other enteric viruses, the researchers note the finding suggests there is potential for exposure through wastewater.
At first, scientists thought Ebola virus could only be transmitted through direct contact with bodily fluids, but cases in the current outbreak have occurred without such direct contact.
The researchers suggest this could mean that the virus is surviving in large droplets of bodily fluids – indicating more care should be taken in handling contaminated liquid waste. They note that an infected patient can produce up to 9 liters of liquid waste per day.
Finally, they comment on the virus’ apparent early demise when it enters wastewater. Perhaps the virus does not decay – perhaps it evades detection by clumping together or attaching to other particles in the water. This would make it much harder to eradicate with disinfectants.
The WHO have already adopted procedures that hold liquid waste contaminated with Ebola for a longer period before releasing it into the sewage system.
Another potential solution might be to pretreat the waste with an antiviral chemical like chlorine, say the researchers, who also caution more information on how well this kind of disinfection might work is needed first.
Prof. Bibby says further research should now be done – that is not confined to the lab – to assess persistence of Ebola in liquid waste through all the steps of disposal and beyond. He concludes:
“These results indicate that further research is needed with a more holistic approach to assessment of Ebola-infected wastewater, from storage to treatment to disposal and continued monitoring, including a precautionary approach to wastewater handling in all epidemic responses.”
Meanwhile, Medical News Today recently learned that doctors working in remote areas may soon have available a paper-strip test for Ebola. The rapid test works like a home pregnancy test and changes color, depending on whether the patient has Ebola, yellow fever or dengue.