The decline of leprosy in Japan: patterns and trends 1964-2008.

OBJECTIVE: Our purpose was to elucidate the patterns and trends of autochthonous leprosy in Japan from 1964 to 2008, to compare them with the findings from other studies of leprosy in decline, and to determine whether M. leprae transmission persists in Japan.

DESIGN: Data on registered leprosy cases in Japan in the period 1964-2008 were analysed with reference to trends in case detection, geographical distribution, age at diagnosis, sex, classification, family history and broad correlation with socioeconomic conditions.

RESULTS: A consistent decline in leprosy case detection was observed in all areas of the country over the period 1964-2008. Highest incidence was consistently in Okinawa, the southernmost part of Japan. Autochthonous leprosy has not been reported in anyone born in Japan since 1980. Increasing average age and a shift towards lower latitudes were demonstrated throughout the period. There was an inverse association between regional measures of wealth and leprosy incidence.

CONCLUSIONS: Leprosy has declined throughout the past century in Japan. Autochthonous transmission has probably stopped in mainland Japan, but may still occur at a low level in Okinawa, the country's southernmost region. Analyses of data on autochthonous cases revealed patterns similar to those reported in other countries with declining leprosy. Detailed comparisons between countries with very low leprosy incidence may help us to better understand the epidemiology of leprosy.