Ebola-infected sewage may require longer holding period

The study co-authored by Lisa M. Casanova, assistant professor of environmental health, and Scott R. Weaver, research assistant professor in Epidemiology and Biostatistics, used bacteriophage Φ6, a type of virus, as a stand-in to study how long Ebola and similar viruses can survive in latrines and other systems for collecting and disposing of sewage. Bacteriophage Φ6 has a lipid envelope, meaning it has structural similarities to Ebola and several other types of virus, allowing for a safe study that did not require use of Ebola itself.

"The places hardest hit by Ebola are the places that often have the least infrastructure for safely disposing of sewage and are using things like pit latrines," said Dr. Casanova. "They need the answers to questions like this."

Their study, "Inactivation of an Enveloped Surrogate Virus in Human Sewage," was published recently in Environmental Science & Technology Letters.

To reduce the risk of infection for sanitary workers, the World Health Organization recommends latrine waste contaminated with Ebola be held for a week or longer before any efforts are made to transport it.

Casanova and Weaver conducted experiments on sewage samples taken from an urban wastewater reclamation facility, spiking the samples with Φ6 as a stand-in for Ebola. Their analysis found that at 86° Fahrenheit (equal to 30° Celsius) the virus was essentially inactivated after 3-7 days. However, samples tested at 72.6° Fahrenheit (or 22°C) took several days longer to decay.

The study suggests longer holding times may be needed where temperatures are lower. Longer holding times may also be advisable to eliminate "longer-surviving subpopulations of viruses."