The role of viruses in human infectious pathology

The global virome (virosphere; unformal domain Viraea) has evolved over at least three billion years through continuous co-evolution with the major domains of life, including Archaea, Bacteria, and Eukarya. All viral pathogens known to cause human infectious diseases are of zoonotic origin, having entered human populations at different stages of human evolution and societal development. This process remains ongoing today. The global virome constitutes an immense reservoir of viruses with pandemic potential. Continuous shaping of viral population gene pools under environmental selective pressures drives the emergence of novel human infections. Certain zoonotic viruses have adapted to sustained human-to-human transmission, becoming anthroponotic or zooanthroponotic pathogens, whereas others remain primarily zoonotic. To date, more than 500 viruses (representing over 180 species) have been identified as causative agents of human infectious diseases. Collectively, viral infections affect nearly the entire global population annually: acute intestinal viral infections account for approximately 6 billion cases, acute respiratory viral infections for 1–5 billion cases, vector-borne viral fevers for 450 million cases, parenterally transmitted viral hepatitis for 3 million new cases, and HIV infection for 1.5 million new cases, resulting in an estimated 10–15 million deaths annually, excluding long-term sequelae. Viruses transmitted via the aerosol route periodically give rise to pandemics associated with millions of deaths. At the time of emergence, humanity is typically unprepared, lacking effective means for prevention and treatment. The annual economic burden attributable to major viral infections–including HIV, parenteral viral hepatitis, and influenza–is estimated at hundreds of billions to trillions of U.S. dollars, while the COVID-19 pandemic alone inflicted global economic losses estimated at USD 8.8 trillion, with long-term consequences projected to reach USD 16 trillion (roughly 10–15% of annual global economic output). Persistent, centuries-long pandemics caused by herpesviruses, papillomaviruses, polyomaviruses, and parvoviruses are associated with oncogenesis and a broad spectrum of systemic diseases, for which preventive and therapeutic options remain limited. Ensuring biological security requires continuous genomic surveillance of the virome across both natural and anthropogenically altered ecosystems. Such surveillance will improve the capacity to predict pandemic emergence and inform strategic approaches to prevention, including vaccine development, as well as antiviral therapies targeting multiple stages of viral life cycle. Fundamental research into virus–host interactions and the pathogenesis of viral infections remains essential for advancing preparedness against current and future viral threats.