virusy

Virusy are microscopic infectious agents that infect living organisms. They are not considered living organisms by all definitions because they cannot reproduce or carry out metabolism outside a host cell. A typical virusy particle contains genetic material—DNA or RNA—encased in a protein coat called a capsid; many also have a lipid envelope derived from the host cell membrane and proteins that help it enter cells. The genome can be single- or double-stranded, linear or circular, and ranges from a few thousand to more than a hundred thousand nucleotides.

Virusy replicate by invading a host cell and using the cell's machinery to synthesize viral components, which assemble into new virusy particles that exit the cell by lysis or budding. Depending on the type, some virusy cause productive infections that destroy the cell, while others establish latent or persistent infections.

Classification typically separates virusy by genome type—DNA viruses and RNA viruses—which are further grouped by structure, replication strategy, and host range. Transmission routes vary and include respiratory droplets, fecal-oral spread, contact with contaminated surfaces, blood or bodily fluids, and vectors such as insects and ticks.

Pathogenicity is variable: many virusy cause mild illness or asymptomatic infections, while others can cause severe disease, trigger immune responses, or contribute to cancer. Prevention and treatment rely on vaccination for many virusy, antiviral drugs for selected infections, and public health measures such as hygiene and surveillance. Virusy are also widely used as tools in molecular biology and medicine, for example in gene delivery and vaccine development.