1. Introduction
Viral gastroenteritis can be caused by enteric viruses (such as norovirus) via waterborne routes. These viruses replicate in the intestinal tract of the infected individual and are then excreted with feces in high concentrations. Enteric viruses have been detected in rivers, reservoirs, and ground waters that are utilized as sources of drinking water (Chigor and Okoh, 2012; Lodder et al., 2010; Sibanda and Okoh, 2013; Steyer et al., 2011; Ye et al., 2012). Normally, the concentrations of virus are low and are sufficiently treated by drinking water treatment plants (DWTPs); however, in the event ofa lapse in one or more of the water treatment processes, it is possible that a large population could be exposed to enteric viruses via tap water. For example, Kukkula & Maunula (1999) reported a tap water-associated norovirus outbreak with an estimated 1700e3000 cases that was caused by inadequate treatment at a DWTP.