Summary
There are some 17,000 notified cases of gastroenteritis in New Zealand each year. This is only a small fraction of the actual cases because many cases are not reported, even though acute gastroenteritis is a notifiable disease. The disease organisms are mainly bacterial (Campylobacteria, Salmonella,Shigella, Yersinia and toxigenic E.coli), protozoal (Cryptosporidia and Giardia) or viral (enterovirus or norovirus).
Although the main sources of infection are food and contact with animals, and waterborne disease is only a fraction of the total disease burden from gastroenteritis, the ESR report estimates that the actual number of waterborne cases lies between 18,000 and 34,000 a year, of which an average of some 145 cases occur in outbreaks, the remaining cases being endemic.