ARF arises from infections by Group A streptococci (GAS) bacteria. Commonly this is experienced as a sore throat (15 to 30 per cent of sore throats in children and 10 per cent in adults) but in Aboriginal communities in the north of Australia, there is evidence that GAS skin infection (impetigo) is possibly a causative factor in the development of ARF. (5) Following infection by GAS, genetically susceptible people go on to develop a generalised autoimmune inflammatory state, affecting connective tissue in the joints, skin, central nervous system and the heart. While some in this group may immediately develop RHD, most commonly it is repeated, often subclinical, episodes of ARF that progressively damage heart valves and lead to RHD. (6)
The onset of ARF occurs most frequently in children aged five to 14 years. Under the age of five, the child's immune system is not sufficiently mature to generate autoimmune conditions; ARF is rarely seen in children under three. Peak incidence of first episodes of ARF occurs in pre-adolescents; in adulthood it becomes rare again. (6,7) While ARF seems to be associated with ethnicity, there is no identified link to ethnic origin. Genetically, susceptibility occurs in between three and six per cent of all populations. (7)