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Virus tropism refers to the virus' preferential site of replication in discrete cell types within an organ. In most cases, tropism is determined by the ability of the viral surface proteins to fuse or bind to surface receptors of specific target cells to establish infection.
How viruses do this depends mainly on the type of nucleic acid DNA or RNA they contain, which is either one or the other but never both. Viruses cannot function or reproduce outside a cell, and are totally dependent on a host cell to survive. Most viruses are species specific, and related viruses typically only infect a narrow range of plants ...
A virus is a submicroscopic infectious agent that replicates only inside the living cells of an organism. [1] Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea. [2] [3] Viruses are found in almost every ecosystem on Earth and are the most numerous type of biological entity.
The human virome is the total collection of viruses in and on the human body. [1] [2] [3] Viruses in the human body may infect both human cells and other microbes such as bacteria (as with bacteriophages). [4] Some viruses cause disease, while others may be asymptomatic.
The virus often infects many tissues, if not the whole plant, where it can continue to replicate. There are a variety of methods the virus can use to spread throughout the organism but the most common route use the vascular system, otherwise known as the xylem and phloem, and the plasmodesmata, which interconnect adjacent cells.
The virus wraps its delicate nucleic acid with a protein shell known as the capsid, from the Latin capsa, meaning "box," in order to shield it from this hostile environment. Similar to how numerous bricks come together to form a wall, the capsid is made up of one or more distinct protein types that repeatedly repeat to form the whole capsid.
[1] The term is variously used to refer to viral particles shedding from a single cell, from one part of the body into another, [2] and from a body into the environment, where the virus may infect another. [3] Vaccine shedding is a form of viral shedding which can occur in instances of infection caused by some attenuated (or "live virus") vaccines.
[1] The term pathogen came into use in the 1880s. [2] [3] Typically, the term pathogen is used to describe an infectious microorganism or agent, such as a virus, bacterium, protozoan, prion, viroid, or fungus. [4] [5] [6] Small animals, such as helminths and insects, can also cause or transmit disease.