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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).
Whether or not viruses are ‘alive’ is a subject of heavy debate across the world. While viruses exhibit some behaviours that can be characterized as 'alive', such as their ability to replicate and evolve, they lack certain essential features typically associated with life, such as cellular structure and independent metabolism. [25]
Nearly 100 percent of people who get infected with the rabies virus will die from it, making it the most lethal known virus. To date, only 14 people have survived the disease after showing symptoms.
Viruses are among the biggest threats to humanity, with the current pandemic showing how these pathogens can shut down countries, halt entire industries and cause untold human suffering as they ...
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.
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 ...
Hepatitis delta virus or hepatitis D virus (HDV) is a small virusoid, the sole member of the Deltavirus genus. It infects humans. It infects humans. A subviral satellite , it can only replicate in the presence of a hepatitis B (HBV) helper virus .