Evaluation of "chemical isolation" in 1,168 leprosy patients' homes.

: Chemical isolation" (treatment of open cases as a measure of control for transmission between contacts) is evaluated by a retrospective study of 7,232 household contacts of 1,168 leprosy patient homes. Contacts comparable in age and type of exposure were arranged in subgroups according to whether they were born before (Group A) or born after (Group B) beginning treatment of the index cases had begun. Additionally, the whole group of contacts, both of open (LL & BB) and closed (TT & I) cases were evaluated. Among comparable contacts of LL and BB cases, the infection rate in the contacts before initiation of treatment is higher than in that of contacts after initiation of treatment. The protection afforded by the treatment to the exposed group (Group B) is on the order of 66%. The morbidity occurring in the group born after the initiation of index case treatment apparently results from partial persistence of infectiousness of the case under treatment.