Norovirus; The Principal Threat of Food Borne Illness World Wide: A Review

Abstract

Gastroenteritis, that was probably due to norovirus, was first described by Zahorsky in 1929 as 'winter vomiting disease'. However the agent was not identified until 1972, when virus particles were first visualised by electron microscopy (EM) in faeces obtained from an outbreak. The outbreak had occurred in 1968 at a school in Norwalk, Ohio, US, with a high attack rate of illness among students and teachers. The illness was characterised by nausea, vomiting and diarrhoea with duration of illness of 12-24 hours. The discovery of the virus through EM was important because this was the first virus detected that was specifically associated with cases of acute gastroenteritis. For decades the role of the virus as a causative agent has been hampered by the insensitivity of microbiological diagnostics. Previously it could not be grown in cell culture and there was no small animal model. The only alternative was to test on human volunteers. To overcome this gap, investigators at Baylor College of Medicine engineered human intestinal tissue from stem cells isolated from the small intestine. When the researchers infected the cultured gut tissue with different strains of norovirus, some virus strains grew well in the cells while others did not. To promote virus growth, the team then tried adding bile from humans and other animals, including cows and pigs, to the intestinal cells. Researchers found that bile was required for replication of some virus strains and enhanced the growth of other strains in the cells. The authors say this new cultivation method could have applications for food safety and the development of new diagnostics, vaccines and therapeutics for norovirus [1].