This family of viruses is ubiquitous in nature, infecting invertebrates, vertebrates and plants. In humans, respiratory enteric orphan viruses infect the human respiratory and intestinal tracts, usually without disease symptoms.
Reoviruses were first recognised in 1959, when they were wrongly classified as echoviruses (Picornaviridae). There are more than 150 species in the family Reoviridae.
The majority of human orthoreoviral infections involve the gastrointestinal and upper respiratory tracts and are asymptomatic, occasionally producing mild febrile illness, or very rarely, serious complications. A type of coltiviral infection causes Colorado tick river fever.