Virus | Definition, Structure, & Facts | Britannica
2024年10月24日 · Virus, infectious agent of small size and simple composition that can multiply only in living cells of animals, plants, or bacteria. Viruses possess unique infective properties and thus often cause disease in host organisms. Learn about the history, types, and features of …
Structure and features of viruses | Britannica
virus, Microscopic, simple infectious agent that can multiply only in living cells of animals, plants, or bacteria. Viruses are much smaller than bacteria and consist of a single- or double-stranded nucleic acid (DNA or RNA) surrounded by a protein shell called a capsid; some viruses also have an outer envelope composed of lipids and proteins ...
Virus - Structure, Capsid, Genome | Britannica
2024年10月24日 · Virus - Structure, Capsid, Genome: The amount and arrangement of the proteins and nucleic acid of viruses determine their size and shape. The nucleic acid and proteins of each class of viruses assemble themselves into …
Coronavirus | Definition, Features, & Examples | Britannica
2024年11月11日 · Coronavirus, any virus belonging to the family Coronaviridae. Coronaviruses have enveloped virions that measure approximately 120 nm in diameter. The genome consists of a single strand of positive-sense RNA (ribonucleic acid). Examples of coronaviruses include the agents that cause SARS, MERS, and COVID-19.
Virus - Infection, Host, Replication | Britannica
2024年10月24日 · Virus - Infection, Host, Replication: Viruses can reproduce only within a host cell. The parental virus (virion) gives rise to numerous progeny, usually genetically and structurally identical to the parent virus.
Ebola | Cause, Symptoms, Treatment, & Transmission | Britannica
2024年11月15日 · Ebola, infectious disease caused by a virus of the family Filoviridae that is responsible for a severe and often fatal viral hemorrhagic fever. In humans, ebolaviruses cause fatality in 25 to 90 percent of cases.
Computer virus | Definition & Facts | Britannica
6 天之前 · Computer virus, a portion of a computer program code that has been designed to furtively copy itself into other such codes or computer files. It is usually created by a prankster or vandal to effect a nonutilitarian result or to destroy data and program code or, in the case of ransomware, to extort payment.
retrovirus - Encyclopedia Britannica
2024年11月8日 · Retrovirus, any of a group of viruses that belong to the family Retroviridae and that characteristically carry their genetic blueprint in the form of ribonucleic acid (RNA). Retroviruses cause tumor growth and certain cancers in animals and are associated with slow infections of animals.
Virus - Infection, Structure, Replication | Britannica
2024年10月24日 · Virus - Infection, Structure, Replication: Although viruses were originally discovered and characterized on the basis of the diseases they cause, most viruses that infect bacteria, plants, and animals (including humans) do not cause disease.
Definition, Symptoms, Treatment, & Prevention - Britannica
2024年11月20日 · Influenza, acute viral infection of the upper or lower respiratory tract, marked by fever, chills, and a generalized feeling of malaise. Influenza is caused by viruses in the family Orthomyxoviridae. Learn more about the classification of influenza viruses, influenza outbreaks, and influenza symptoms and treatment.