Rheumatic heart disease is caused by rheumatic fever, which is a sequela of strep throat infections. It is a major cause of mitral valve insufficiency and stenosis globally, with 15 million cases worldwide and over 200,000 deaths in 2008. In India, it commonly affects children aged 5-15, with a prevalence of 5-7 cases per 1,000 children. The severity of valve damage depends on factors like the number of previous rheumatic fever attacks, time between onset and treatment, and sex. Prevention involves treating strep throat infections aggressively with benzathine penicillin injections over multiple years.