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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.
The average virus is about 1/100 the size of the average bacterium, and most are too small to be seen directly with an optical microscope. The origins of viruses are unclear: some may have evolved from plasmids, others from bacteria. Viruses are sometimes considered to be a life form, because they carry genetic material, reproduce and evolve ...
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.
Germ theory denialism is the pseudoscientific belief that germs do not cause infectious disease, and that the germ theory of disease is wrong. [1] It usually involves arguing that Louis Pasteur's model of infectious disease was wrong, and that Antoine Béchamp's was right.
With flu, RSV (respiratory syncytial virus) and the common cold, experts say, people are generally most infectious between a day or two before symptoms begin and then for a few days afterward.
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 ...
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).
That it became infectious to humans through escape from a laboratory where it was being studied is a minority position. The available evidence supports zoonosis. [43] [18] Although the origin of SARS-CoV-2 is not definitively known, arguments used in support of a laboratory leak are characteristic of conspiratorial thinking. [18]