I thank Dr Porzecanski for pointing out an inconsistency in my article. 

The 1950s marked the time when immigration patterns began to change in Canada. There was a post-war surge in the number of immigrants initially mainly from Europe with few from Asia and other high TB-prevalence countries. 

This pattern began rapidly to reverse and resulted in reduction and eventually leveling in the rate of decline of disease which subsequently resumed its downward pattern. Rates of course were dropping in the 1950s due to the introduction of effective treatment, and this point should have been clarified.

—Kevin Elwood, MD
Vancouver