Persistence of Ebola Virus in Sterilized Wastewater

Abstract

In the wake of the ongoing 2014/2015 Ebola virus outbreak, significant questions regarding the appropriate handling of Ebola virus-contaminated liquid waste remain, including the persistence of Ebola virus in wastewater. To address these uncertainties, we evaluated the persistence of Ebola virus spiked in sterilized domestic sewage. The viral titer decreased approximately 99% within the first test day from an initial viral titer of 10⁶ TCID₅₀ mL^-1; however, it could not be determined if this initial rapid decrease was due to aggregation or inactivation of the viral particles. The subsequent viral titer decrease was less rapid, and infectious Ebola virus particles persisted for all 8 days of the test. The inactivation constant (k) was determined to be -1.08 (2.1 days for a 90% viral titer decrease). Due to experimental conditions, we believe these results to be an upper bound for Ebola virus persistence in wastewater. Wastewater composition is inherently heterogeneous; subsequently, we caution that interpretation of these results should be made within a holistic assessment, including the effects of wastewater composition, dilution, and potential exposure routes within wastewater infrastructure. While it remains unknown if Ebola virus may be transmitted via wastewater, these data demonstrate a potential exposure route to infectious Ebola virus via wastewater and emphasize the value of a precautionary approach to wastewater handling in an epidemic response.

Figure 1

Persistence of an initial Ebola virus concentration of 10⁶ TCID₅₀ mL^–1 in domestic wastewater (untreated sewage) (A) including the time zero time point and (B) excluding the time zero time point to mitigate potential aggregation effects. Linear trendlines are shown. Fit inactivation constants (k) were determined to be −1.08 when including time zero and −0.35 when excluding time zero. Error bars are ±1 standard deviation.