Due to immunity acquired in childhood, most adults are not susceptible to rotavirus; gastroenteritis in adults usually has a cause other than rotavirus, but asymptomatic infections in adults may maintain the transmission of infection in the community. Virology
Transmission
Rotavirus is transmitted by the faecal-oral route, via contact with contaminated hands, surfaces and objects, and possibly by the respiratory route. The faeces of an infected person can contain more than 10 trillion infectious particles per gram;  fewer than 100 of these are required to transmit infection to another person.Rotaviruses are stable in the environment and have been found in estuary samples at levels as high as 1–5 infectious particles per US gallon. Sanitary measures adequate for eliminating bacteria and parasites seem to be ineffective in control of rotavirus, as the incidence of rotavirus infection in countries with high and low health standards is similar. Types
There are five species of rotavirus, referred to as A, B, C, D and E. Humans are mostly infected by species A. All five species cause disease in other animals. Within rotavirus A there are different strains, called serotypes. As with influenza virus, a dual classification system is used based on two  proteins on the surface of the virus. The glycoprotein VP7 defines the  G serotypes and the protease-sensitive protein VP4 defines P serotypes. Because the two genes that determine G-types and P-types can be passed on separately to progeny viruses, different combinations are found.
The progeny viruses are released from the cell by lysis. Pathophysiology
The diarrhoea is caused by multiple activities of the virus. Malabsorption occurs because of the destruction of gut cells called enterocytes. The toxic rotavirus protein NSP4 induces age- and calcium ion-dependent chloride secretion, disrupts SGLT1 transporter-mediated reabsorption of water, apparently reduces activity of brush-border membrane disaccharidases, and possibly activates the calcium ion-dependent secretory reflexes of the enteric nervous system. Healthy enterocytes secrete lactase into the small intestine; milk intolerance due to lactase deficiency is a symptom of rotavirus infection, which can persist for weeks. A recurrence of mild diarrhoea often follows the reintroduction of milk into the childs diet, due to bacterial fermentation of the disaccharide lactose in the gut. Diagnosis
Diagnosis of infection with rotavirus normally follows diagnosis of gastroenteritis as the cause of severe diarrhoea. Most children admitted to hospital with gastroenteritis are tested for rotavirus A. Specific diagnosis of infection with rotavirus A is made by finding the virus in the childs stool by enzyme immunoassay. There are several licensed test kits on the market which are sensitive, specific and detect all serotypes of rotavirus A. Other methods, such as electron microscopy and PCR, are used in research laboratories. Reverse transcription-polymerase chain reaction (RT-PCR) can detect and identify all species and serotypes of human rotavirus. Prevention
Because improved sanitation does not decrease the prevalence of rotaviral disease, and the rate of hospitalisations remains high, despite the use of oral rehydrating medicines, the primary public health intervention is vaccination.