Seasonal prevalence of potentially infectious enteric viruses in surface waters below treated wastewater discharge

Enteric viruses are widely distributed in the natural water environment. The aim of the study was to assess the prevalence of potentially infectious adenoviruses (AdV) and rotaviruses (RoV) in surface water near treated wastewater discharge.

Water samples were collected from surface water below the treated wastewater effluent discharge located near a wastewater treatment plant receiving sewage from an urban area. Water samples were concentrated by ultrafiltration and treated with propidium monoazide dye, followed with v-qPCR/v-RT-qPCR analysis. Simultaneously, the temperature and pH of the collected samples were measured to check the influence of these parameters on the concentrations of potentially infectious viruses.

The average concentrations of potentially infectious AdV and RoV particles in collected samples ranged between log₁₀ 1.86 ÷ 3.94 gc/L and log₁₀ 2.39 ÷ 3.82 gc/L in the winter season, and between log₁₀ 2.18 ÷ 3.59 gc/L and log₁₀ 1.85 ÷ 2.10 gc/L in the summer season, respectively. In general, AdVs were detected more often than RoVs, while RoV-positive samples were more frequent in the winter than in the summer season (Chi²: p = 0.028; Fisher's Exact test p = 0.033). Negative correlations between log10 concentration of viral particles and temperature and pH for both viruses were observed.

The presence of potentially infectious AdVs and RoVs in the surface waters may constitute a health risk for the local population. Application of v-PCR-based methods and considering AdV as a viral contamination indicator should be introduced into virological water quality monitoring for estimations of public health risks.