Introduction: Conventional wastewater treatment processes significantly reduce but do not completely remove viral genetic material. This narrative review (2000–2025) synthesizes evidence on the presence and persistence of viral genomes, particularly RNA from coronaviruses such as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), in sewage and sludge, distinguishing these detectable genetic signals from infectious viruses.
Methods: A literature search was conducted in PubMed, Scopus, Web of Science, Science Direct, and Google Scholar. Keywords included “virus,” “coronavirus,” “SARS-CoV-2,” “sewage,” “sludge,” “concentration,” “detection,” and “quantification.” After screening 1,350 records, 152 studies meeting the inclusion criteria (peer-reviewed studies on human viruses in municipal sewage/sludge, published between 2000 and 2025) were included.
Results: SARS-CoV-2 RNA was detected in raw sewage at concentrations up to 10⁶ copies/L during the 2020 peak, declining to 10³–10⁴ copies/L by 2025. In sludge, SARS-CoV-2 RNA persisted at 10³–10⁵ copies/g dry weight after anaerobic digestion, with only a 1–2 log₁₀ reduction. Viral genomes of other pathogens (adenoviruses [AdVs], noroviruses [NoVs], hepatitis E virus [HEV], and rotaviruses [RoVs]) were also frequently identified. Notably, the reviewed studies reported the detection of viral RNA, not the isolation of infectious virions.
Conclusion: Viral genomes, especially coronavirus RNA, are not fully eliminated during wastewater and sludge treatment and can persist in the environment. This persistence underscores the utility of wastewater-based epidemiology for surveillance. However, the detection of RNA does not
indicate the presence of an infection risk, as standard treatment processes effectively inactivate viable viruses.