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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.
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.
It does this by making the cell copy the virus's DNA or RNA, making viral proteins, which all assemble to form new virus particles. [37] There are six basic, overlapping stages in the life cycle of viruses in living cells: [38] Attachment is the binding of the virus to specific molecules on the surface of the cell. This specificity restricts ...
A viral disease (or viral infection) occurs when an organism's body is invaded by pathogenic viruses, and infectious virus particles (virions) attach to and enter susceptible cells. [ 1 ] Examples include the common cold , gastroenteritis , COVID-19 , the flu , and rabies .
The name of the family, Poxviridae, is a legacy of the original grouping of viruses associated with diseases that produced poxes on the skin.Modern viral classification is based on phenotypic characteristics; morphology, nucleic acid type, mode of replication, host organisms, and the type of disease they cause.
The pause in communications also caused the cancellation of a meeting between the CDC and IDSA about threats to public health regarding the H5N1 influenza virus. [ 35 ] On February 14, 2025, around 1,300 CDC employees were laid off by the administration, which included all first-year officers of the Epidemic Intelligence Service . [ 36 ]
The polyhedral capsid from which the virus gets its name is an extremely stable protein crystal that protects the virus in the external environment. It dissolves in the alkaline midgut of moths and butterflies to release the virus particle and infect the larva. [20] An example of an insect that it infects is the fall webworm. [21]
Like other members of the Paramyxoviridae family, it produces enveloped virions, and is a negative-sense single-stranded RNA virus. The virus is particularly fragile and is quickly inactivated by heat, desiccation, and sunlight. [14] Measles virus evolved from the then-widespread rinderpest virus most probably between the 11th and 12th ...