The epidemiology of acute rheumatic fever (ARF) is closely connected with that of group-A beta haemolytic streptococcal pharyngitis, both have a maximum incidence in the age group of 5-15 years. In India, the average age at presentation is between 10 and 14 years.
However, the early development (under 5 ayears) of established rheumatic heart disease and rapid progression to mitral stenosis poses a major problem in India and has been labelled as "Juvenile Mitral Stenosis".
On occasions, it may occur in older persons as is seen in the epidemics occurring in closed population like military recruits, crowded living conditions and those in contact with school children. In adults, it is mostly seen in the second and early third decade of life. It is more common in the winter season when the GAS pharyngitis is also on the rise. It still remains a major health problem in developing countries.
In the west, there was a peak incidence in the early years of twentieth century, but with socioeconomic improvement when overcrowding was reduced and penicillin prophylaxis was started, there was a decline. But again there has been resurgence in USA during the last 2 decades inspite of improved standard of living, improved medical care. This has been attributed to rise of virulent GAS infections.
Epidemics of ARF in USA closely followed GAS infections. Also reports from China of Cyclical rise and fall in the incidence of ARF has been noted. Hence the current hypothesis is that there is a cyclical rise and fall of virulent cones of GAS, with respect to time and spread these organisms which results in cyclical outbreaks of ARF.