Disease has afflicted humans ever since there have been humans. Malaria and tuberculosis are thought to have ravaged Ancient Egypt more than 5,000 years ago. From AD 541 to 542 the global pandemic known as “the Plague of Justinian” is estimated to have killed 15–25% of the world’s 200-million population. Following the Spanish conquest of Mexico, the native population dropped from around 30 million in 1519 to just three million 50 years later. Today we are battling to control the spread of COVID-19, which has the potential to cause the most deadly pandemic in human history.