The onset of cold weather brings out the boots, coats, gloves – and the block-lettered, stoplight-red “Flu Shots Available Here” signs in drugstore windows. And with good reason. For many scientists and public health specialists alike, flu season has become a little like Russian Roulette. The likelihood of a deadly pandemic outbreak of influenza is not far from reality considering the nature of some of the different viral strains. In this eBook, we delve into the science of the flu, starting with past pandemics and what we can learn from them. The book opens with a story on how scientists were able to analyze the viral strain that caused the 1918 pandemic, known as the “Spanish flu,” which was so shocking in symptoms and virulence that physicians first thought they were dealing with a new infection. The next sections examine the sources, transmission and surveillance of the virus, including how and why zoonoses – infectious diseases that originate from animals – are vaulting to the top of health officials’ risk lists. A universal vaccine is the Holy Grail of defense against the quickly mutating virus, and two expert interviews discuss the ongoing quest. However, with research comes controversy. Recent studies into the dreaded bird flu, or H5N1, raised serious questions about access to information versus the threat of bioterrorism. Is it possible to practice both good science, which thrives on the free flow of information, and good defense, which thrives on the opposite? While there are no definitive answers to this and other issues, these pages analyze the science behind the controversy, providing an essential resource to understanding this potentially deadly virus.