1900 -1940's Tuberculosis took the lives of students at canadian church run residential schools for at least 40 years. Abuse of students at residential schools continued for many years.
 http://www.theglobeandmail.com/news/politics/natives-died-in-droves-as-ottawa-ignored-warnings/article754798/

Documents in the Canadian National Archives reveal that children continued to die from tuberculosis (TB) at alarming rates for at least four decades after a senior official at the Department of Indian Affairs initially warned in 1907 that schools were making no effort to separate healthy children from those sick with the highly contagious disease.

It is argued that the canadian government's handling of the situation, combined with Canada's official policy of removing children from their homes for 10 months each year to attend distant schools, does indeed fit the United Nations definition of genocide. The UN definition, adopted after the Second World War, lists five possible acts that qualify as genocide, of which killing is only one. The fifth act is described as “forcibly transferring children of the group to another group.” In 2000, four years after the last residential school closed, the government finally adopted a limited definition of genocide, excluding the line about forcible transfer of children. But courts have rejected native claims of genocide against Ottawa and the churches because Canada had no law banning genocide while the schools were operating.

The focus was on killing native culture in the name of assimilation.
 http://hiddenfromhistory.org/