Influenza is a disease that strikes in two forms. Seasonal influenza returns each winter, killing up to half a million people in bad years and causing much misery. Pandemic influenza, by contrast, is rare - having occurred only a handful of times in the last century - and far worse than seasonal flu, often killing many millions across the world. The worst pandemic of all, the “Spanish Flu” of 1918, killed over twice as many people as the First World War - some estimates are even higher. Since 1918, our understanding of influenza virus has come a long way. We can now trace how the pandemics of the last hundred years originated in bird flu and swine flu, and we can model the evolution of the virus from year to year, aiding vaccine design. We also have some anti-viral drugs that can be used in emergencies, and we understand more about how flu is transmitted and possible ways to prevent its spread. In this free online course, we will cover everything from the history of influenza to modern laboratory diagnostics and vaccination. You’ll learn about the annual cycle that brings seasonal flu to our shores every winter, and also how avian and pig flus can contribute to the emergence of new pandemic strains of flu. We’ll also look at the structure of the virus in more detail, seeing how the study of influenza is now carried out at the molecular level. As well as mini-lectures, there will be laboratory demonstrations, interviews with experts in a variety of relevant fields, and discussion sessions, where you’ll be invited to contribute your own experiences and opinions to the subject of flu, and how we should treat and prevent it. You can find out more in Dr Derek Gatherer’s post for the FutureLearn blog: “Do I have the flu? And 5 more common questions about influenza”.