1348: The Black Death arrived in England, quickly spreading and causing the death of almost 2 and a half million people, leading to the death of almost 1/3 of Europe's population
John Snow found the cause of cholera in dirty water in Britain in 1831, leading to the creation of London's sewage system by Joseph Bazalgette to prevent cholera
Discovery of 'magicbullets' - chemicals that could kill microbes causing disease while leaving the body unharmed, including the use of chloroform as an anesthetic