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Often we just think of a few viruses—influenza, HIV, and now coronaviruses—but viruses are the most plentiful microbes on the planet. Of those, about 320,000 types of viruses infect mammals ...
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 virus is transmitted by exposure to infectious blood or some body fluids. Mother-to-child transmission is a major route in endemic countries. HBV is 50–100 times more infectious than HIV. The virus replicates in liver cells, and enters the blood where viral proteins and antiviral antibodies are found.
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).
When the virus replicates faster than the immune system can control, it can destroy cells and harm the body, and it can even incite an over-zealous immune reaction that can cause other damage.
Virus classification showing major ranks This is a list of biological virus families and subfamilies. See also Comparison of computer viruses. This is an alphabetical list of biological virus families and subfamilies; it includes those families and subfamilies listed by the ICTV 2023 report. [1] For a list of individual species, see List of ...
Getting sick this winter? We talked to a UC Davis infectious diseases expert about what to know.
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.