Estimates of the burden of foodborne disease rely on attributing a proportion of syndromic gastroenteritis to foodborne transmission. Persons with syndromic diarrhoea/vomiting can also present with concurrent respiratory symptoms that could be due to respiratory infections, gastrointestinal infections, or both. This distinction is important when estimating the foodborne disease burden but has rarely been considered. Using data from population surveys from Australia, Canada and the USA we describe the effect of excluding persons with respiratory and associated symptoms from the case definition of gastroenteritis. Excluding persons first with respiratory symptoms, or second with respiratory symptoms plus fever and headache, resulted in a decrease in the weighted estimates of acute gastroenteritis of about 10-50% depending on the exclusion criteria. This has the potential to have a very significant impact on estimates of the burden of foodborne infections using syndromic case definitions of acute gastroenteritis.