Int. J. Environ. Res. Public Health 2012, 9 911 noticed by the inhabitants prior to the occurrence of outbreak, thus indicating leakages in the pipelines. The information available from the affected localities indicated that the water supplying pipes were more than 100 years old and that unauthorized and unclaimed pipelines existed for water connection. Since the daily water supply in this area was intermittent, back siphoning of sewage water in the drinking water supplying pipes could not be ruled out. Subsequently, clusters of cases who developed diarrhea and/or vomiting were reported from a single locality in a short period representing rampant infections of gastroenteritis [43,44]. These findings highlight the possible enhancing impact of the sewage contamination on the endemic transmission of prevalent and emerging strains of enteric viruses. Notably, majority of the viral agents (RVA, NoV, AdV, HAstV and EV) detected in the patients affected by outbreaks showed the presence of more than one genotype/serotype indicating diverse nature of enteric viral pathogens. Thus, this report provides strong evidence of the cocirculation of multiple enteric viruses in Mumbai, the biggest cosmopolitan city of India. To the best of our knowledge, this is the first report from India that documents coexistence of seven (RVA, RVB, NoV, AdV, HAstV, EV and AiV) important enteric viruses in the outbreak cases of acute gastroenteritis and emphasizes the need to investigate such outbreak cases in different parts of India to evaluate the health risk associated with enteric viral pathogens in Indian population. 5. Conclusions This investigation reports association of seven different enteric viruses in two outbreaks of gastroenteritis in Mumbai, India, one of the most densely populated cities in the World. Virological examination of the faecal specimens from the outbreaks ascertained the predominance of RVAs and EVs in the study population. Therefore, intervention strategies need to be developed against these viral infections. Occurrence of two outbreaks within seven months period in the same region emphasizes the need for constant vigilance of water supply and drainage systems to reduce the risks of such incidences. Overall, the study ratifies the need for continuous surveillance of outbreaks of gastroenteritis in Mumbai and also in other parts of India for identifying the prevalent and new enteric viruses. Acknowledgements Authors thank A.C. Mishra, National Institute of Virology, Pune for constant support, P.H. Singare and S. Sengupta, Grant Medical College and J.J. group of Hospitals, and J.E. Thanekar, Public health Department, Mumbai for extending their cooperation in collection of clinical samples from patients with gastroenteritis. Authors also thank V.D. Khanande, Health Services, Pune, for providing information on annual occurrence of gastroenteritis outbreaks at state level and Cecilia Dayaraj for help provided in revising the manuscript. Technical help of P.S. Jadhav is duly acknowledged. Conflict of Interest The authors declare no conflict of interest.