Medical advances allow people to live longer and healthier lives. Penicillin is developed in time to save lives during the Second World War. After the war national public health institutions are established, and national and international efforts are directed towards treatments against infectious diseases including typhus, tuberculosis and polio. Smallpox, the scourge of developing countries, is also eradicated. As deaths from infectious diseases are reduced, population booms in those developing countries with high birth rates – China and India take measures to promote family planning. Cholera becomes a risk in countries with insufficient sanitation to prevent water-borne diseases. AIDS spreads in Africa and elsewhere, and unlike other diseases appears untreatable. By the 1990s health in the developing world has much improved, and reduced infant mortality rates have lowered birth rates across the world. The introductory scene shows the United States in the 1950s when polio was prevalent.