Omicrons.org is a plain-language guide to viral evolution: how viruses are built, why RNA viruses such as SARS-CoV-2 mutate, how variants like Omicron emerge and are tracked, and the computational methods researchers use to study them. It is written for students and curious readers.
Virus structure, genome types, capsids and envelopes, and how viruses are classified. Start reading.
The seven human coronaviruses and how SARS-CoV-2 enters cells through the ACE2 receptor.
Why RNA viruses mutate quickly and how natural selection turns rare advantageous mutations into new variants.
Articles on computational science, data analytics and managing large scientific datasets. See the articles.
Educational information only — not medical advice. For health guidance, consult a qualified professional or your public health authority.
Understanding how viruses evolve, spread, and cause disease — from basic biology to pandemic science
Virology is the branch of microbiology concerned with viruses — submicroscopic, non-cellular agents that replicate only inside the living cells of organisms. Viruses infect all life forms, from animals and plants to fungi and bacteria. The study of viruses is fundamental to medicine, public health, evolutionary biology, and biotechnology.
All viruses share certain structural features. At minimum, a virus consists of genetic material (either DNA or RNA) enclosed in a protein coat called a capsid. Many viruses also have an outer lipid membrane (envelope) derived from the host cell membrane. The combination of capsid and envelope (if present) is called the virion — the extracellular, infectious form of the virus.
Viruses are classified by several criteria:
Coronaviruses (family Coronaviridae) are enveloped, positive-sense, single-stranded RNA viruses with the largest known RNA genomes (~26–32 kilobases). They derive their name from the crown-like appearance of their surface spike proteins under electron microscopy (Latin: corona = crown). Seven human coronaviruses are known:
SARS-CoV-2, the causative agent of COVID-19, uses its spike protein's receptor-binding domain to attach to ACE2 (angiotensin-converting enzyme 2) receptors on human cells. Once attached, the spike protein undergoes conformational changes that fuse viral and host cell membranes, allowing viral RNA to enter the cytoplasm. The positive-sense RNA is directly translated by host ribosomes to produce viral proteins, including the RNA-dependent RNA polymerase (RdRp) that replicates the viral genome.
RNA viruses mutate rapidly because RNA polymerases lack proofreading mechanisms, introducing approximately one error per 10,000 nucleotides copied. For SARS-CoV-2 with its ~30,000 nucleotide genome, this means roughly one to three mutations per replication cycle. Most mutations are deleterious or neutral, but occasionally a mutation confers a replicative advantage — higher ACE2 binding affinity, faster replication, better immune evasion, or more efficient transmission. Such advantageous mutations are amplified by natural selection, potentially giving rise to new variants.
Get the best content from Omicrons delivered straight to your inbox.