Reoviruses are comprised of 10 to 12 double-stranded RNA genomic segments that can reassort both in nature and in laboratory settings. The most common mammalian isolates are type 1 (Lang), type 2 (Jones), and type 3 (Dearing).

Reoviruses have a high endemic infection rate in many mammals, such as primates, cattle, horses, cats, dogs, rodents and swine. These viruses are common in raw water sources and are often found along with other animal viruses. In humans, the viruses cause only asymptomatic or mild respiratory infections. However, research suggests that reoviruses may be associated with potentially more severe illnesses. Reoviruses have been linked to neonatal hepatitis, extrahepatic biliary atresia, meningitis and myocarditis. Also, immunocompromised, young and elderly individuals may become susceptible to severe bacterial respiratory disease due to an initial reovirus infection.

Due to their widespread occurrence and the ability of these viruses to survive a long period of time in the environment, contamination of water sources has been frequently reported. Animals are especially prone to infection by these viruses. Xenotransplantation of animal organs is severely endangered by potential contamination with these viruses.

Diagnosis of reovirus infection by nonmolecular means is very difficult and is usually based on virus isolation on cell cultures and electron microscopy. These methods are not very sensitive (Muscillo et al., 2001) and are likely underestimate the presence of these viruses in animals and humans. Molecular detection by PCR is the most sensitive, rapid and specific method for identifying reoviruses.