Medicine in the 20th century "tamed" most of the incurable deadly infectious diseases of the past. For some, it offered complete cure, while for others, long-term management and treatment of symptoms. However, the recent COVID-19 pandemic reminded us that our daily lives can be dramatically disrupted by new and unknown infectious diseases. Thus, we remembered how a virus can push health systems to the brink of collapse and force us to take health protection measures. I mention the word "remembered" because humans, like other forms of life on our planet, have encountered and been infected by unknown viruses for millions of years.

In the book you hold in your hands, I try to provide through my own perspective a broader picture of these strange "exotic" parasites and the significance they have played in shaping human existence and life as we know it on this planet. Among historical epidemics and scientific-philosophical questions about the essence of life, I attempt to introduce the not unjustly misunderstood entities of viruses. It is worth getting to know them because through them we can see the reflections of our own journey and existence.