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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.
A virus with this "viral envelope" uses it—along with specific receptors—to enter a new host cell. Viruses vary in shape from the simple helical and icosahedral to more complex structures. Viruses range in size from 20 to 300 nanometres; it would take 33,000 to 500,000 of them, side by side, to stretch to 1 centimetre (0.4 in).
Some viruses can "hide" within a cell, which may mean that they evade the host cell defenses or immune system and may increase the long-term "success" of the virus. This hiding is deemed latency. During this time, the virus does not produce any progeny, it remains inactive until external stimuli—such as light or stress—prompts it to activate.
Of those, about 320,000 types of viruses infect mammals but there are just 219 known to infect humans, according to the U.S. National Library of Medicine. 52 Things You Need to Know About Viruses ...
Gamma phage, an example of virus particles (visualised by electron microscopy) Virology is the scientific study of biological viruses.It is a subfield of microbiology that focuses on their detection, structure, classification and evolution, their methods of infection and exploitation of host cells for reproduction, their interaction with host organism physiology and immunity, the diseases they ...
Often simply called an antiviral. A class of antimicrobial medication used specifically for treating diseases caused by viral infections rather than ones caused by bacteria or other infectious agents. Unlike most antibiotics, antivirals typically do not destroy their target viruses but instead inhibit their development. They are distinct from virucides. assembly The construction of the virus ...
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 are the common cold , gastroenteritis , corona , flu , pneumonia .
Viruses infect all life forms; therefore the bacterial, plant, and animal cells and material in the gut also carry viruses. [6] When viruses cause harm by infecting the cells in the body, a symptomatic disease may develop. Contrary to common belief, harmful viruses may be in the minority, compared to benign viruses in the human body.