Noroviruses "(genus Norovirus, family Caliciviridae) are a group of related, single-stranded RNA, non-enveloped viruses that cause acute gastroenteritis in humans. The most common symptoms of acute gastroenteritis are diarrhea, vomiting, and stomach pain. Norovirus is the official genus name for the group of viruses previously described as “Norwalk-like viruses” (NLV)."
"Noroviruses spread from person to person, through contaminated food or water, and by touching contaminated surfaces. Norovirus is recognized as the leading cause of foodborne-disease outbreaks in the United States." In 2011, a study found that noroviruses are not sufficiently eliminated in treated sewage sludge that is used as fertilizer on food crops.