Rotaviruses are the most common cause of diarrhoeal disease among infants and young children. Nearly every child in the world is infected with a rotavirus at least once by the age of five. Immunity develops with each infection, so subsequent infections are less severe; adults are rarely affected. There are ten species of the genus, referred to as A, B, C, D, E, F, G, H, I and J. Rotavirus A, the most common species, causes more than 90% of rotavirus infections in humans.
The virus is transmitted by the faecal-oral route. It infects and damages the cells that line the small intestine and causes gastroenteritis (which is often called “stomach flu” despite having no relation to influenza). Rotaviral enteritis is a mild to severe disease characterised by nausea, vomiting, watery diarrhoea and low-grade fever.
Symptomatic infection rates are highest in children under two years of age and decrease progressively towards 45 years of age. Severe symptoms tend to occur in children six months to two years of age, the elderly, and those with immunodeficiency.