Viruses in humans can be traced back to the 1900s. Smallpox and measles are the oldest, and as of 2012, 219 virus species affecting humans were identified. Among them are Yellow fever, influenza, Zika, Polio, Human Immunodeficiency Virus (HIV), Ebola and Corona virus, which was discovered in 2019. Viruses were discovered over a period of time through rigorous processes which continue to be utilized with the application of new knowledge, which makes new findings modify and rediscover their inevitability. What in the World are Viruses? Each chapter in this book helps the reader sift through individual themes of well-researched and articulated articles for easy understanding written to contribute towards building on existing knowledge on viruses. The impact of viruses on humans cannot be ignored, especially in this era where the world is grappling with the effects of Corona Virus that has claimed many lives worldwide. The impact of virus outbreaks on a macro scale in society has been felt globally with disruptions of economies and livelihoods. Against this background, this publication explores the importance of studying viruses, particularly their effect on individuals. A chapter in the book looks at how a virus affects society, unearthing how a pandemic affects the global supply chain, how easily hospitals can become overwhelmed, the economic impact of viruses, and the positive impact that viruses have on society. Effects make the issue of viruses of utmost importance to study. Researching on viruses has improved knowledge to find solutions through vaccines' discovery, identifying preventive measures to eradicate the danger that viruses present to humans. Anti-viral treatments are available in the world today as a solution to fight against viruses. With this, many lives have been saved as people continue to access treatment. Although controversies surrounding viruses exist, they do not deter research on viruses from continuing. Information contained in this publication will add value to your knowledge base; this is why you should take time to read and enjoy the book.