exposed to contaminated food or liquids exposed to contaminated food or liquids exposed to contaminated food or liquids exposed to contaminated food or liquids norovirus exposed to contaminated food or liquids Norovirus Norovirus Norovirus norovirus Norovirus avoiding noroviruses Norovirus exposed to contaminated food or liquids Norovirus exposed to contaminated food or liquids exposed to contaminated food or liquids Norovirus exposed to contaminated food or liquids exposed to contaminated food or liquids exposed to contaminated food or liquids 20 million cases of gastroenteritis a year. exposed to contaminated food or liquids