Human adenoviruses as waterborne index pathogens and their use for Quantitative Microbial Risk Assessment Marco Verani a , Ileana Federigi a, ⁎, Gabriele Donzelli a , Lorenzo Cioni b , Annalaura Carducci a a Laboratory of Hygiene and Environmental Virology, Department of Biology, University of Pisa, Via S. Zeno 37, 56127 Pisa, Italy b Scuola Normale Superiore, P.zza dei Cavalieri, 7, 56126 Pisa, Italy HIGHLIGHTS • HAdV quantification in different water samples in parallel with fecal indicators • 64% of samples positive for HAdV, decreasing from WWTP (100%) to seawaters (21%) • HAdV occurrence in seawater samples complied with excellent EU bathing water criteria • Significant correlation between HAdV and somatic coliphages in less polluted waters • HAdV to indicators ratios modelled as probability density functions for QMRA GRAPHICAL ABSTRACT abstract article info Article history: Received 31 May 2018 Received in revised form 22 September 2018 Accepted 22 September 2018 Available online 25 September 2018 Editor: Paola Verlicchi The current microbial water quality standards are based on the monitoring of fecal indicator organisms, which are mainly bacterial indicators (i.e., Escherichia coli, intestinal enterococci), however epidemiological data indi- cate that viruses are important etiological agents of waterborne illnesses. Among waterborne viruses, human ad- enovirus can be considered as an index pathogen, owing to its abundance in sewage and persistence in the environment, as well as its potential infectivity. In this study, data on human adenoviruses from different water matrices (the entrance and exit of a water treatment plant, rivers and seawaters) were analyzed, in parallel with traditional fecal bacterial indicators and somatic coliphages. The results showed a 64% frequency of positive adenovirus samples, decreasing from the sewage system (100% at the entrance and 94% at the exit) to rivers (92% and 72% for different rivers) and seawater (21%). Adenovirus concentrations showed a significant correlation with somatic coliphages in one river and seawater, thus supporting the recent inclusion of coliphages as viral in- dicators in water safety guidelines. The data collected were used to estimate adenovirus to indicator ratios, which could be used as input in Quantitative Microbial Risk Assessment (QMRA) studies. © 2018 Published by Elsevier B.V. Keywords: Human adenovirus Escherichia coli Intestinal enterococci Somatic coliphages QMRA Water safety 1. Introduction The fecal pollution of waters used for different purposes (potable, reuse or recreation) is a public health issue. The consumption of, or con- tact with, contaminated waters is associated with outbreaks caused by Science of the Total Environment 651 (2019) 1469–1475 ⁎ Corresponding author. E-mail addresses: marco.verani@unipi.it (M. Verani), ileana.federigi@biologia.unipi.it (I. Federigi), gabriele.donzelli@for.unipi.it (G. Donzelli), lorenzo.cioni@sns.it (L. Cioni), annalaura.carducci@unipi.it (A. Carducci). https://doi.org/10.1016/j.scitotenv.2018.09.295 0048-9697/© 2018 Published by Elsevier B.V. Contents lists available at ScienceDirect Science of the Total Environment journal homepage: www.elsevier.com/locate/scitotenv