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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.
A problem for early scientists was that they did not know how to grow viruses without using live animals. The breakthrough came in 1931, when American pathologists Ernest William Goodpasture and Alice Miles Woodruff grew influenza, and several other viruses, in fertilised chickens' eggs. [11] Some viruses could not be grown in chickens' eggs.
Whether or not viruses should be considered as alive is controversial. [ 33 ] [ 34 ] They are most often considered as just gene coding replicators rather than forms of life. [ 35 ] They have been described as "organisms at the edge of life" [ 36 ] because they possess genes , evolve by natural selection, [ 37 ] [ 38 ] and replicate by making ...
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 ...
The cell was first discovered by Robert Hooke in 1665, which can be found to be described in his book Micrographia. In this book, he gave 60 observations in detail of various objects under a coarse, compound microscope. One observation was from very thin slices of bottle cork. Hooke discovered a multitude of tiny pores that he named "cells".
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.
Viral evolution is a subfield of evolutionary biology and virology that is specifically concerned with the evolution of viruses. [1] [2] Viruses have short generation times, and many—in particular RNA viruses—have relatively high mutation rates (on the order of one point mutation or more per genome per round of replication).
The pandemic killed 40–50 million people in less than a year, [48] but the proof that it was caused by a virus was not obtained until 1933. [49] Haemophilus influenzae is an opportunistic bacterium which commonly follows influenza infections; this led the eminent German bacteriologist Richard Pfeiffer (1858–1945) to incorrectly conclude ...