MT1 (metabolic type 1) clone is frequently associated with invasive "Streptococcus pyogenes" infections among developed countries. The incidence and mortality of "S. pyogenes" was high during the pre-penicillin era, but had already started to fall prior to the widespread availability of penicillin. Therefore, environmental factors do play a role in the "S. pyogenes" infection. Incidence of "S. pyogenes" is 2 to 4 per 100,000 population in developed countries and 12 to 83 per 100,000 population in developing countries. "S. pyogenes" infection is more frequently found in men than women, with highest rates in the elderly, followed by infants. In people with risk factors such as heart disease, diabetes, malignancy, blunt trauma, surgical incision, virus respiratory infection, including influenza, "S. pyogenes" infection happens in 17 to 25% of all cases. GAS secondary infection usually happens within one week of the diagnosis of influenza infection. In 14 to 16% of childhood "S. pyogenes" infections, there is a prior chickenpox infection. Such "S. pyogenes" infection in children usually manifests as severe soft tissue infection with onset 4 to 12 days from the chickenpox diagnosis. There is also 40 to 60 times increase in risk of "S. pyogenes" infection within the first two weeks of chickenpox infection in children. However, 20 to 30% of "S. pyogenes" infection does occur in adults with no identifiable risk factors. The incidence is higher in children (50 to 80% of "S. pyogenes" infection) with no known risk factors. The rates of scarlet fever in UK was usually 4 in 100,000 population, however, in 2014, the rates had risen to 49 per 100,000 population. Rheumatic fever and rheumatic heart disease (RHD) usually occurs at 2 to 3 weeks after the throat infection, which is more common among the impoverished people in developing countries. From 1967 to 1996, the global mean incidence of rheumatic fever and RHD was 19 per 100,000 with the highest incidence at 51 per 100,000.