Objective: The objectives of this study were to explore how frequently group A streptococci (GAS) were giving additional cases of clinical GAS tonsillitis within the households and to analyse predictors for such spread of GAS infection.
Setting: Two Norwegian general practice populations in Stokke and Kongsberg communities.
Patients: 110 households with at least one member with sore throat lasting less than 7 days, and GAS demonstrated in throat culture. Among the 110 index patients 51 (46%) were parents, 35 mothers and 16 fathers; 23 were children 6 years and younger, while 36 were children aged 7-15 years.
Main outcome measures: Frequency of spread of clinical GAS infection to another household member within 4 weeks. Distribution of age and size of household in families with and without spread of GAS infection.
Results: In 30 (27%) households one or more new cases of GAS tonsillitis was found, adding 40 new infections. No spread of GAS disease was found in households with only adult members. A significantly higher proportion of spread was found in households with 4 or more members compared with households with fewer members, and low age of the index person. Short duration of symptoms before seeing a doctor was also associated with spread of GAS. In a logistic regression analysis carried out in the households with children, short duration of symptoms before diagnosis and treatment and low age of index person were significantly associated with spread of the infection.
Conclusions: Even with standard penicillin treatment, GAS infection is frequently spread within households, and most frequently in households with children and many members.