virojen

Virojen, the Finnish term for viruses, are microscopic infectious agents that cannot reproduce outside a living cell. They consist of genetic material—DNA or RNA—encased in a protein coat called a capsid; some viruses also have a lipid envelope derived from host membranes. Because they require host cellular machinery to replicate, viruses are considered obligate intracellular parasites.

Viruses are highly diverse in size, shape, and genetic composition. They are commonly classified by genome type (DNA or RNA), genome polarity and strand number, and the structure of the capsid. A widely used framework is the Baltimore classification, which groups viruses by how they generate messenger RNA and replicate. Other classifications consider host range (plants, animals, fungi, bacteria) and the presence or absence of an outer envelope.

Replication and life cycle follow a general pattern but can vary. A virus attaches to specific receptors on a prospective host cell, enters the cell, and releases its genome. The viral genome is copied and translated using the host’s machinery to produce new viral components, which are then assembled into progeny virions and released to infect new cells. Some viruses integrate into the host genome and establish latent infections. Transmission methods differ by virus and can include respiratory droplets, bodily fluids, vectors such as insects, and environmental reservoirs.

Impact and control: viruses cause a wide range of diseases in humans, animals, and plants, from mild illnesses to life-threatening conditions. Public health strategies include vaccination, antiviral therapies, hygiene measures, and surveillance. In biotechnology and medicine, viral vectors are used to deliver genes in research and therapeutic contexts.