Polio is a highly infectious virus that mostly affects young children, attacking the nerves and causing paralysis that can be permanent, and sometimes death. It spreads through contaminated food and water and passes from person to person. Vaccines, both oral and injected, have brought cases down by more than 99 percent since the 1980s. Only smallpox has been fully eradicated so far, and polio is close enough that the remaining transmission hot spots are the focus.

Hampi is a UNESCO World Heritage Site in Karnataka, India, with more than 1,600 surviving remains spread over 4,100 hectares. It was the capital of the Vijayanagara Empire from 1336 to 1565. Travellers from Persia and Portugal described it as a prosperous, wealthy and grand city with temples, markets and farms along the Tungabhadra River. By 1500 it was estimated to be the world's second-largest city after Beijing, and probably India's richest at the time. In 1565 a coalition of Muslim sultanates defeated the Vijayanagara Empire, its capital was conquered and destroyed, and the city was left in ruins. Hampi remains a religious centre, with the active Virupaksha Temple at its heart.