Leprosy trends in northern Thailand: 1951-1990.

Data of new, previously untreated leprosy patients from 6 northern provinces of Thailand, diagnosed at McKean Rehabilitation Center, Chiang Mai and associated clinics between 1951 and 1990 were analysed. The following trends were found: 1) Decreasing numbers of new, previously untreated patients. 2) Increasing average age of patients at onset and presentation of disease. 3) Decreasing duration between onset and presentation. 4) Increasing percentage of patients presenting within the first year of symptoms. 5) Increasing percentage of paucibacillary cases. 6) Decreasing percentage of patients presenting with deformity. These trends are a reflection of those seen for the whole of Thailand and indicate that leprosy control is being effective. Patients are presenting at an earlier stage than before, with consequent reduction in disability and infectivity. Better usage of chemotherapy since 1976 has helped to reduce the transmission of bacilli from person to person, combined with effective health education activities which have dispelled some wrong ideas about leprosy and encouraged patients to seek help early in the course of the disease. Additional factors related to public health and living standards have also contributed.