virusesare

virusesare is a term used to describe viruses as a class of microscopic infectious agents that are obligate intracellular parasites. They are not cells and cannot reproduce on their own; replication occurs only inside living host cells using the host's machinery, often with help from viral enzymes. Most viruses consist of genetic material—DNA or RNA—enclosed in a protective protein coat called a capsid; many also possess a lipid envelope derived from host membranes. The genome may be single- or double-stranded, linear or circular, and can be segmented in some viruses. Viral genomes encode a limited set of proteins necessary for replication and assembly, relying on host cell components for transcription and translation.

Taxonomy of viruses is diverse and evolves with new data. The Baltimore classification groups viruses by genome type and replication strategy, while the ICTV provides a comprehensive, standardized taxonomy. Viruses infect organisms across all domains of life, including bacteria (bacteriophages), archaea, and eukaryotes. The life cycle typically includes attachment to a cell-surface receptor, entry and uncoating, genome replication and gene expression, assembly of progeny virions, and release from the host cell. Some bacteriophages can follow lytic or lysogenic pathways.

Transmission routes vary: respiratory or oral, sexual, blood or bodily fluids, and vectors such as insects. Diseases range from mild to severe and can have public health impacts, though many viruses also exist without causing disease or even confer benefits to ecosystems. Detection and prevention rely on vaccines, antiviral drugs, diagnostics such as PCR, and public health strategies. The history of virology spans from early observations of filtered infectious agents to modern molecular characterization, shaping our understanding of biology and medicine.