Norovirus and other Caliciviruses

Abstract

Norovirus is ubiquitous, associated with 18% (95% CI: 17–20%) of acute gastroenteritis (AGE) worldwide, with similar proportions of disease in high-, middle-, and low- income settings. Norovirus is estimated to cause approximately 200,000 deaths annually worldwide, with about 70,000–100,000 among children in developing countries. In both high- and middle-income countries with mature rotavirus vaccination programs, norovirus is now also the most common cause of pediatric gastroenteritis requiring medical care. Norovirus is extremely contagious and humans are the only known reservoir for human norovirus. Transmission occurs via direct person-to-person, foodborne, waterborne or through environmental fomites. Noroviruses are a group of non-enveloped, single-stranded RNA viruses with an icosahedral symmetry classified into the genus Norovirus of the family Caliciviridae. Other genera within this virus family include Sapovirus, which also causes AGE in humans. Infections in humans are caused by viruses of genogroup (G) I, II and IV for norovirus and by GI, II, IV and V for sapoviruses. Since human norovirus and sapovirus cannot be routinely grown in cell culture, detection of the virus relies on sensitive molecular methods such as real-time reverse transcription polymerase chain reaction. In the environment, norovirus can be found in any water that comes into contact with human stool samples which can also lead to contaminated crops (irrigation) and shellfish (growing waters).