Int. J. Environ. Res. Public Health 2012, 9 896 norovirus (NoV, 12.1% and 10%), rotavirus B (RVB, 12.1% and 10%), enteric adenovirus (AdV, 6.1% and 7.5%), Aichivirus (AiV, 3% and 7.5%) and human astrovirus (HAstV, 3% and 0%). Mixed viral infections were largely represented by two viruses (84.6% and 88.9%), a small proportion showed presence of three (7.7% and 11%) and four (7.7% and 0%) viruses in the two outbreaks. Genotyping of the viruses revealed predominance of RVA G2P[4], RVB G2 (Indian Bangladeshi lineage), NoV GII.4, AdV-40, HAstV-8 and AiV B types. VP1/2A junction region based genotyping showed presence of 11 different serotypes of EVs. Although no virus was detected in the tested water samples, examination of both water and sewage pipelines in gastroenteritis affected localities indicated leakages and possibility of contamination of drinking water with sewage water. Coexistence of multiple enteric viruses during the two outbreaks of gastroenteritis emphasizes the need to expand such investigations to other parts of India. Keywords: adenovirus; gastroenteritis outbreak Aichivirus; astrovirus; enterovirus; norovirus; rotavirus; 1. Introduction Acute gastroenteritis is the third leading cause of mortality in the World [1]. The causative agents of gastroenteritis include bacteria, parasites and viruses. The viruses associated with gastroenteritis are rotaviruses (RVs), calciviruses [noroviruses (NoVs) and sapoviruses (SaVs)], enteric adenoviruses (AdVs), human astroviruses (HAstVs), Aichiviruses (AiVs), toroviruses, coronaviruses and picobirnaviruses [2]. Enteroviruses (EVs) have been also found to be associated with acute gastroenteritis [3]. Recently, Sali/Klasseviruses are also enlisted as enteric viral pathogens [4]. RVAs and RVBs, members of the family Reoviridae, carry a double stranded RNA genome, 18.5 kb in size, with 11 gene segments. Based on the characteristics of VP6, the major structural protein, RVAs are divided into seven groups (A-G). RVAs known to infect young humans and animals have been classified into 27 G and 35 P types on the basis of VP7 (G, glycoprotein) and VP4 (P, protease sensitive) proteins, respectively [5]. RVBs are genetically and antigenically distinct from RVAs and have been found to infect humans and different species of animals. RVB infections have been identified in China, Bangladesh, India and Myanmar to date and often found to cause infections in adolescents and adults and occasionally in children [6,7]. NoVs, members of the family Caliciviridae, possess a single-stranded RNA genome of 7.5–7.7 kb and have been classified into five major groups, Genogroup I (GI) to Genogroup V (GV). GI, GII and GIII have been subdivided into eight, 21 and two genetic clusters, respectively, whereas GIV and GV have one cluster each [8]. Enteric AdVs carrying DNA of 33-45 kb belong to the family Adenoviridae. Based on the biological and genetic characteristics, AdVs are classified into six subgenera, A–F that include more than 51 human AdV serotypes. Among these, subgenera ‘F’ carrying AdV types 40 and 41 and “A” carrying AdV types 12, 18 and 31 have been found to be associated with acute gastroenteritis [9,10]. HAstVs belong to the family Astroviridae and carry RNA genome of 6.8–7.6 kb