[Pulmonary Mycobacterium kansasii infection in Okayama, Japan].

Our group discovered the first patient with pulmonary M. kansasii infection in Okayama Prefecture in 1976. The first case and another ten more patients over about eight years came exclusively from the southern seaside area of Kurashiki City (Mizushima Marine Industrial District and its vicinity). Thereafter, the cases of pulmonary M. kansasii infection have spread geographically and chronologically from the Mizushima district to neighboring areas in the prefecture. We considered the possibility of human-to-human transmission of M. kansasii by both the observed geographic spread and the existence of at least two occupational clusters (three welders working on the same line in the same factory building and nine workers in one ironworks), but we could not resolve several controversial problems.