<unk>  typically colonizes the throat, genital mucosa, rectum, and skin. Of healthy individuals, 1% to 5% have throat, vaginal, or rectal carriage. In healthy children, such carriage rate varies from 2 to 17%. There are four methods for the transmission of this bacterium: inhalation of respiratory droplets, skin contact, contact with objects, surface, or dust that is contaminated with bacteria or, less commonly, transmission through food. Such bacteria can cause a variety of diseases such as streptococcal pharyngitis, rheumatic fever, rheumatic heart disease, and scarlet fever. Although pharyngitis is mostly viral in origin, about 15 to 30% of all pharyngitis cases in children are caused by<unk> ; meanwhile, 5 to 20% of pharyngitis in adults are streptococcal. The number of pharyngitis cases is higher in children than in adults due to exposures in schools, nurseries, and as a consequence of lower host immunity. Cases of Streptococcal pharyngitis occur more frequently in later winter to early spring in seasonal countries due to many people rebreathing the same indoor air. Disease cases are the lowest during autumn. MT1 (metabolic type 1) clone is frequently associated with invasive<unk>  infections among developed countries. The incidence and mortality of<unk>  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<unk>  infection. Incidence of<unk>  is 2 to 4 per 100,000 population in developed countries and 12 to 83 per 100,000 population in developing countries.<unk>  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,<unk>  infection happens in 17 to 25% of all cases.<unk>  secondary infection usually happens within one week of the diagnosis of influenza infection. In 14 to 16% of childhood<unk>  infections, there is a prior chickenpox infection. Such<unk>  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<unk>  infection within the first two weeks of chickenpox infection in children. However, 20 to 30% of<unk>  infection does occur in adults with no identifiable risk factors. The incidence is higher in children (50 to 80% of<unk>  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. Maternal<unk>  infection usually happens in late pregnancy; at more than 30 weeks of gestation to four weeks postpartum, which accounts for 2 to 4% of all the<unk>  infections. This represents 20 to 100 times increase in risk for<unk>  infections. Clinical manifestations are: pneumonia, septic arthritis, necrotizing fasciitis, and genital tract sepsis. According to a study done by Queen Charlotte's hospital in London during the 1930s, the vagina was not the common source of such infection. On the contrary, maternal throat infection and close contacts with carriers were the more common sites for maternal<unk>  infection.
Streptococcus pyogenes
Staphylococcus aureus
Streptococcus bovis
Streptococcus mutans
Pseudomonas aeruginosa
Staphylococcus haemolyticus
Neisseria flavescens
Corynebacterium diphtheriae