There are a total of 424 Viruses that have been compiled and organized in this comprehensive list. The selection includes clinically relevant human pathogens, notable zoonotic and emerging viruses, ICTV-verified taxa, and well-documented strains from CDC, WHO and peer-reviewed literature.

Viruses are microscopic infectious agents that require living cells to replicate and cannot reproduce on their own. They range from small RNA viruses to large, complex DNA viruses and infect animals, plants and microbes. Many cause disease in humans and other hosts, while others shape ecosystems and drive evolution. Researchers also use viruses in vaccines, gene therapy and molecular biology.

Interesting and little-known facts about Viruses:
– There are roughly 10^31 virus particles on Earth, making them the most numerous biological entities.
– ICTV has classified thousands of virus species, yet environmental sequencing suggests millions more remain undescribed.
– Giant viruses such as mimivirus are larger than some bacteria and carry hundreds of genes.
– RNA viruses typically have higher mutation rates than DNA viruses, fueling rapid evolution and variant emergence.
– An estimated 60–75% of emerging human infectious diseases are zoonotic, originating from animal hosts.

The alphabetical A–Z index links to each letter’s list for quick reference. Each letter lists name; ICTV classification (family/genus/species); “Affects humans?” Yes/No with brief qualifier; common symptoms (5–10 words); primary transmission; typical hosts; and key references.

Sources: ICTV, Centers for Disease Control and Prevention (CDC), World Health Organization (WHO), PubMed literature. Last updated: March 9, 2026.