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Viruses are able to initiate infection, disperse throughout the body, and replicate due to specific virulence factors. [2] There are several factors that affect pathogenesis. Some of these factors include virulence characteristics of the virus that is infecting.
Some bacteria, such as Streptococcus pyogenes, are able to break down the host's immunoglobulins using proteases. Viruses also have notable virulence factors. Experimental research, for example, often focuses on creating environments that isolate and identify the role of "niche-specific virulence genes".
Bacteria and viruses are often lumped together as germs, and they share many characteristics. They’re invisible to the human eye. They’re everywhere.
The binding is due to electrostatic interactions and is influenced by pH and the presence of ions. The virus then releases its genetic material (either single- or double-stranded RNA or DNA) into the cell. In some viruses this genetic material is circular and mimics a bacterial plasmid. At this stage the cell becomes infected and can also be ...
Viruses display a wide diversity of sizes and shapes, called 'morphologies'. In general, viruses are much smaller than bacteria and more than a thousand bacteriophage viruses would fit inside an Escherichia coli bacterium's cell. [39]: 98 Many viruses that have been studied are spherical and have a diameter between 20 and 300 nanometres.
For the viruses that infect bacteria, the bacteriophages, the bacteria growing in test tubes can be used directly. For plant viruses, the natural host plants can be used or, particularly when the infection is not obvious, so-called indicator plants, which show signs of infection more clearly. [36] [37] Cytopathic effect of herpes simplex virus.
Bacteria such as Mycobacterium leprae and Treponema pallidum can be grown in animals, although serological and microscopic techniques make the use of live animals unnecessary. Viruses are also usually identified using alternatives to growth in culture or animals. Some viruses may be grown in embryonated eggs. Another useful identification ...
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.