GAS upper respiratory tract infection is highly contagious; the organism often is quite prevalent among children as well as adults. Two settings that have a major influence in the epidemiology of GAS are the school and the home/family. To date, the relative influence of these two settings on the epidemiology has been incompletely defined. To assess the influence of these different environs on the spread of GAS, a 9-month prospective population-based study was conducted in a semi-closed community. 187 subjects(75% of those eligible) were studied with frequent clinical evaluations and throat cultures (TC); 60% were school-age. The mean number of visits was 11 per subject (range 10-13). 2112 TC were obtained. The overall positivity rate was 24%. Symptomatic subjects with positive TC were treated. 85% of GAS were type M-28.

Point prevalence rates (PR) for individual grades ranged from 0% (grade 11) to 85% (grade 4), compared with family point PR which ranged from 0% to 70%. Grade school age children had higher PR for each visit when compared with high school children and adults. Comparing prevalence by grade, grades 4 and 5 had a higher cumulative PR for the entire 9-month period (60%) than did other grades (35%) (p<0.001). Wide variation in cumulative PR was also evident among the families. Assessing a possible association between grade and family prevalence, 87% of the 4th grade and 50% of the 5th grade were from families with a cumulative PR of ≥ 25%. In contrast, only 35% of children from the remaining grades were from families with cumulative PR ≥ 25%. Families with children in either the 4th or 5th grade were 3 times more likely to acquire GAS than those with children in other grades (risk=2.89, χ2=79.58, p<0.001). Mothers and/or siblings in close contact with a colonized child appeared more likely to acquire the organism.

Conclusion: This prospective study in a semi-closed community indicates that both the schoolroom and the home play significant, yet distinct roles in the spread of GAS.