Today the deadly poliomyelitis virus is only endemic to four countries – Afghanistan, India, Nigeria, and Pakistan. This is thanks to the groundbreaking research undertaken by doctor and biologist Jonas Salk. In 1947, at the University of Pittsburgh, Salk combined his work on the influenza vaccine with his search for a vaccine to protect against poliomyelitis. The virus was deadly in 5 to 10 percent of cases where patients became paralysed, and thus were unable to breathe. Medical opinion at the time held that only a live virus could prompt total immunity, but Salk disproved this. In 1952 he used formaldehyde, a gas with a strong smell, to inactivate the poliomyelitis virus and developed a vaccine still capable of triggering an immune response in a host. Initially tested on monkeys, then human patients, Salk’s success convicted him to test it on himself, his family, his staff, and other volunteers.