Studies on the role of the famiy unit in the transmission of trachoma.

Rates of trachoma infection of family members were compared for two groups of index cases; all were infants about 1 year old observed over a period of several months in a previous study. Group A infants were consistently infected with trachoma, and Group B infants were not infected with trachoma. On the average, 50% of Group A family members had active infection (as determined by trachoma inclusions in their conjunctival cells) and 80% of the siblings within 6 years of age to the index cases were infected. Only 9% of Group B family members had active trachoma, and 20% of the siblings within 6 years of age to the index case were infected. This study suggests intrafamilial spread of trachoma.