The plethora of miscommunication and disinformation about how SARS-CoV-2 (COVID-19) spreads suggests a widespread misunderstanding of how viruses work. This book will focus on the interpretation of scientific and medical results, giving the reader guidance on interpreting virological data, including the concepts of 'live' versus infectious virus. The first section covers the background of virology and immunology, introducing the reader to the science of virology (using COVID-19 as an illustration) and considers the measurement of infectious disease, using polymerase chain reaction (PCR), molecular biology and the immune system. The second section looks at clinical virology and neurovirology. Taking a novel perspective on how viruses may play a role in evolution, this book discusses antivirals and how autoimmune disorders may be caused or triggered by viruses. Concise and practical, this is a key resource for those working in neurology, infectious disease and virology.