Entrance into the food is the result of poor hygiene, ill food handlers, or the use of unpasteurized milk. Food sources include sausage, evaporated milk, cheese, meat croquettes, meat pie, pudding, raw milk, and pasteurized milk. Group A infections are low and may occur in any season, whereas Group D infections are variable. Streptococcal sore throat is very common, especially in children. Usually it is successfully treated with antibiotics.
Complications are rare and the fatality rate is low.
Diarrheal illness is poorly characterized, but is acute and self-limiting. No age or race susceptibilities have been found. Suspect food is examined microbiologically by selective enumeration techniques which can take up to 7 days. Group specificities are determined by Lancefield group-specific antisera. Salad bars have been suggested as possible sources of infection.