Norwalk virus - Off and running

Proportion of Sporadic Gastroenteritis Cases Caused by Rotavirus, Norovirus, Adenovirus and Bacteria in Japan from January 2000 to December 2003

Many kinds of virus and bacterium have been identified as pathogens that cause sporadic gastroenteritis (SG). Among the pathogens, rotavirus (RV), norovirus (NV; previously known as Norwalk-like virus), and adenovirus (AdV) types 40/41 have been considered as the prevalent viruses implicated in the aetiology of childhood gastroenteritis. In the present study, we attempted to estimate monthly proportions of SG cases caused by the viral agents (RV, NV, AdV and other viruses (OV)) and bacterial agents in the whole of Japan. The estimation was carried out by using time series data of the incidence of SG and the viral and bacterial agents of SG, which were collected by a nationwide surveillance system in Japan from January 2000 to December 2003. It was confirmed that, in the dominant period of RV and NV, the proportion of RV-associated SG and that of NV-associated SG indicate almost same level with each other: 46-69% during February-May for RV, and 41-75% during October-December for NV.

Is norovirus a foodborne or pandemic pathogen? An analysis of the transmission of norovirus-associated gastroenteritis and the roles of food and food handlers

This study examined the association of norovirus with foodborne disease outbreaks linked to food handlers and foodborne outbreaks of acute gastroenteritis associated with norovirus, in comparison to Salmonella foodborne gastroenteritis. Comparative analysis using chi(2)-tests showed no similarity between the outbreaks from norovirus and those from Salmonella. Odds ratios also showed a stronger similarity between the proportions of food handler-implicated norovirus outbreaks than from Salmonella-implicated outbreaks. An analysis of data found norovirus transmission to occur more frequently spread person-to-person, unlike Salmonella, but similar to influenza or rotavirus. Norovirus was also not shown to be associated with food consumption. The data collection tool that focuses on food handlers as a source of the virus may be better including the general human population. Such an enteric virus would be better understood through its similarity to the person-to-person transmission model resulting in pandemic spread.