virión

A virion is the complete, infectious form of a virus outside of a host cell. It consists of genetic material, usually DNA or RNA, enclosed within a protein coat called a capsid. Some viruses also have an outer lipid envelope derived from the host cell membrane. The virion's structure is designed for efficient transmission and entry into host cells, where it can replicate.

The capsid's shape can vary, with common forms including helical, icosahedral, and complex. The genetic material within the capsid contains the instructions for the virus to replicate. The presence or absence of a lipid envelope is a key characteristic used in classifying viruses. Enveloped viruses are generally more susceptible to environmental factors like detergents and heat, while non-enveloped viruses are typically more robust.

The primary function of a virion is to deliver its genetic material to a susceptible host cell. Once inside the cell, the viral genetic material hijacks the host's cellular machinery to produce more viral components, which then assemble into new virions. These new virions are released from the host cell, often leading to its destruction, and are then capable of infecting other cells, perpetuating the viral infection cycle. The study of virions is fundamental to virology, providing insights into viral structure, replication, and pathogenesis.