Geographical and Chronological Spread of Pulmonary Mycobacterium kansasii Infection in Okayama, Japan

Abstract

Our group discovered the first patient in Okayama prefecture with pulmonaryMycobacterium kansasii infection in 1976. This first case and several more patients who were treated by our group over about eight years came exclusively from the southern, seaside area of Kurashiki City (Mizushima Marine Industrial District and its vicinity). Thereafter, a few cases of pulmonaryM. kansasii infection appeared at hospitals in different areas of Okayama prefecture. In 1984, our group therefore used questionnaires to survey the prevalence ofM. kansasii infection in 30 major hospitals located in various areas of the prefecture; this procedure was repeated in 1994. As a result, it was found that 105 cases had occurred between 1976 and December 1993. The author also found thatM. kansasii infection has apparently spread from the Mizushima district to neighboring areas in the prefecture (i.e., from a southern urban area to northern rural areas). Although we did not investigate mycobacteria in tap water of the affected areas, and several controversial problems remain, 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) suggest the possibility of human-to-human transmission ofM. kansasii.