Virionernes

Virionernes refers to the complete, infective form of a virus that exists outside a host cell and enables transmission between hosts. A virion is designed to protect the viral genome and to deliver it into a susceptible cell, where infection can begin. Virions can be enveloped, possessing a lipid envelope with embedded glycoproteins, or non-enveloped, consisting only of a protein coat around the genome.

The core of a virion typically contains either DNA or RNA as its genetic material, packaged within a protective capsid made of viral proteins. In enveloped virions, the envelope is derived from host membranes and often includes matrix or tegument proteins that assist in assembly and early steps after entry. The capsid arrangement can be icosahedral, helical, or more complex, reflecting different virus families. The outer surface features receptor-binding proteins that determine host range and tissue tropism, influencing which cells a virion can attach to and enter.

Outside a host, virions vary in environmental stability. Enveloped virions are generally more sensitive to drying, heat, and detergents, while non-enveloped virions tend to be more resistant. Transmission routes include respiratory droplets, bodily fluids, fecal-oral pathways, vectors, and direct contact. Upon reaching a new host, virions attach to specific receptors, enter cells by endocytosis or membrane fusion, and release their genome for replication. Viral assembly then produces new virions that exit to infect additional cells or hosts.

In research and medicine, virions are central to understanding virology, vaccine development, diagnostics, and antiviral strategies. Quantification of virions, such as via titer measurements, helps assess infection risk, immune responses, and the efficacy of interventions.