In much of the western world, the trajectory of health as a right was linked to fundamental negotiations over the "social contract" between state leaders and civil society. In Latin America, most decisive debates over states' responsibilities for public health, and health as a citizenship right, took shape in the twentieth century. Governments began to recognize their role in designing and administering health programs and negotiated their responsibilities and duties. Since the first decades of the past century, the development of health systems at the nation-state level was also influenced by powerful international agencies that mediated new "social contracts" in modernizing nations. Historians have portrayed philanthropic "missionaries of science," like the Rockefeller Foundation (RF), for example, that contributed to the suppression of health threats such as yellow fever and malaria.