The opportunist mycobacteria--a 20-year retrospect.

A review is presented of the incidence and distribution of infections with opportunist mycobacteria in Wales for the years 1952-71. The most important opportunist pathogen was Although the numbers affected by each species were small, taken together they indicate a genuine increase in incidence over the two decades. As tuberculosis declined by five-sixths over the same period, the relative change has been striking. The distribution of infections suggest that exposure to dust at work and to heavy air pollution at home predispose to infection by opportunist mycobacteria.