Viruss

Viruss is not a standard scientific term in biology; the correct form is virus (plural viruses). In scientific usage, a virus is a small infectious agent that can replicate only inside living cells. Viruses are composed of genetic material, either DNA or RNA, surrounded by a protein coat called a capsid, and in many cases a lipid envelope derived from host membranes.

Virus genomes vary in type and size. They may carry double-stranded or single-stranded DNA, or single-stranded or double-stranded RNA. Within these broad categories, genomes can be positive-sense or negative-sense RNA, segmented or continuous. Because of these differences, viruses are classified using systems such as the Baltimore classification, which groups them by genome type and replication strategy.

Viruses do not carry out metabolic processes on their own and rely on host cells to reproduce. The general life cycle includes attachment to a specific receptor, entry into the cell, replication of the genome and production of viral proteins, assembly of new virions, and release from the host cell, often by lysis or budding. Some viruses can integrate their genetic material into the host genome and persist for extended periods.

Viruses infect a wide range of hosts, including bacteria (bacteriophages), plants, and animals. Transmission routes vary widely and can involve airborne particles, direct contact, bodily fluids, vectors, or contaminated surfaces. The impact of viral infections ranges from asymptomatic to severe disease.

Detection and prevention rely on laboratory methods such as PCR, genome sequencing, and serology to identify infections. Vaccination, antiviral medications, and public health measures reduce transmission and disease burden. The study of viruses, virology, covers their biology, evolution, ecology, and interactions with hosts. Historical discoveries by scientists such as Ivanovsky and Beijerinck helped establish the concept of viruses.