Decay and Solid-Liquid Partitioning of Mpox and Vaccinia Viruses in Primary Influent and Settled Solids to Guide Wastewater-Based Epidemiology Practices

Wastewater-based epidemiology (WBE) has proven to be a powerful tool for tracking the spread of viral pathogens, such as SARS-CoV-2, but as WBE has expanded to include new pathogens, such as mpox virus, more data is needed to guide practitioners on how to design WBE campaigns. Here, we investigated the decay rates of heat-inactivated mpox (HI-MPXV) and attenuated vaccinia virus (VV) in primary influent and settled solids collected from a local POTW at 4°C, 22°C, or 35°C using digital PCR. Subsequently, we studied the solid-liquid partitioning of the viruses in primary influent. Over the 30-day study period, we observed no significant difference in log-linear decay rates between viruses (p=0.5258), with significantly higher decay rates in primary influent (0.109-0.144/day) compared to settled solids (0.019-0.040/day) at both 22°C (p=0.0030) and 35°C (p=0.0166). Furthermore, as part of the partitioning experiment, we found that HI-MPXV and VV adsorb to the solids fraction of primary influent at higher intensities than previously studied enveloped viruses (K _F = 1,000-31,800 mL/g, n = 1.01-1.41). Likewise, it was determined in the partitioning experiment that a concentration of greater than 10 ³ gc/mL in raw influent was needed for the viable quantification of mpox and vaccinia viruses in the clarified liquid fraction of raw primarily influent. Our study provides essential insights into informative sample collection and storage conditions for the analysis of wastewater and for transport modeling studies. Due to the slow decay observed in settled solids at all tested temperatures in the persistence experiment, this matrix may be most suitable for retrospective analyses of community infection of the mpox virus.