A family outbreak of serious streptococcal infection.

A localized outbreak of scarlet fever was caused by an M-nontypable T-1 (NT/1) group A beta-hemolytic Streptococcus. The result was a fatal outcome in a 5-year-old child and a near fatality in his 10-year-old sibling. The outbreak was confined to family units that had members with whom the children were close playmates. Extensive epidemiologic studies in neighborhood schools and local hospital emergency rooms did not demonstrate a disemination of the causative serotype in the community.