Hospital Wastewater as a Clinically Relevant Hotspot of Emerging Contaminants: Multidrug-Resistant Pathogens, Virulence Determinants, and the Challenge of Effluent Treatment

Hospital wastewater (HWW) is a concentrated clinical–environmental interface in which pharmaceutical residues, disinfectants, diagnostic compounds, pathogenic microorganisms, antimicrobial-resistant bacteria, antimicrobial resistance genes (ARGs), virulence determinants, and mobile genetic elements coexist. This review synthesises the evidence on HWW as a reservoir of priority pathogens, from the sink drains and P-traps inside the building—where biofilms of carbapenemase-producing Enterobacterales and Pseudomonas aeruginosa have been genomically linked to patient infection—to the effluent that reaches municipal networks. Culture-based, genomic, and metagenomic studies across multiple geographical settings have recovered ESKAPEE organisms, WHO priority pathogens, clinically important antimicrobial resistance genes (ARGs), and mobile resistance platforms from hospital effluents; fungal (Candidozyma auris, azole-resistant Aspergillus fumigatus), viral, and protozoan pathogens are recovered far less often but appear to be systematically under-investigated rather than absent. Residual antimicrobials and quaternary ammonium disinfectants sustain selection at concentrations well below therapeutic doses. Conventional treatment reduces bulk organic and microbial load but does not uniformly eliminate micropollutants, viable resistant organisms, ARGs, or mobile elements; membrane bioreactors, activated carbon, ozonation, ultraviolet irradiation, and advanced oxidation perform better, but each performs well against some endpoints and poorly against others. We therefore propose a conceptual endpoint-based framework that separates four complementary domains—chemical, microbiological, genetic, and functional/ecological—and use it as an interpretive tool to show that percentage-removal claims are difficult to interpret unless the endpoint domain is specified. Hospital effluent management should be treated as an infection-prevention problem as much as an environmental one, integrated into One Health antimicrobial-resistance strategies through drain-level source control, molecular surveillance, endpoint-specific performance criteria, and regulation that extends beyond conventional physicochemical compliance.