Viral persistence in soil: Insights from qPCR and cell culture detection of adenovirus

Abstract

Microbial risks represent a major public health concern in the sustainable reuse of wastewater and land application of biosolids. Accurate quantitative data on viral particle numbers and persistence in soil are essential for robust risk assessment. This study compared the reliability of two detection methods for human adenovirus (HAdV) in soil under varying environmental conditions. Soil samples inoculated with HAdV type 5 were monitored over time under different seasons (summer and winter) and light exposures (direct sunlight and shade). Viral concentrations were measured at specific intervals using both a cell culture assay on HeLa cells and quantitative real-time PCR (qPCR). Our results indicated an inactivation rate of 0.36-0.93 day-1 for HAdV using the cell culture method, whereas qPCR analysis showed a much lower inactivation rate of viral particles (0.005-0.04 day-1) during the study period. The results demonstrated that the cell culture method detected a significant, environment-dependent reduction in infectious virus, with faster inactivation during summer and under sunlight. In contrast, qPCR revealed no substantial decline in viral genomes over the study period. These findings indicate that, although qPCR is highly sensitive and rapid, it cannot reliably reflect the persistence of infectious viral particles or accurately assess associated health risks. Such information is critical for informed decision-making in public health protection and environmental policy development.