We explain what viruses are, their morphology, and the infection process. In addition, its characteristics, classification, and mode of transmission.
Viruses are a kind of microscopic and acellular parasitic agents (which are not made of cells ), capable of reproducing only inside a host cell, generally using their genetic replication mechanisms and causing damage in the process.
Viruses are capable of infecting any form of life , from animals and plants to bacteria and other viruses (virophages), and they exist in all terrestrial ecosystems, being the most abundant known biological form: more than 5,000 virus species have been described since its discovery in 1899, but it is estimated that there could be millions of them.
The origin of viruses is uncertain , since there are various theories about it. Some suppose that they could have evolved from plasmids (free-living DNA fragments), and others that they could come from bacteria or other cellular organisms, despite the fact that their structure is much simpler than theirs.
What virologists do agree on is that these are very primitive organisms in the history of life , despite the fact that there are no viral fossil records. Known and preserved virus species date back no more than 90 years. On the other hand, viruses have an enormous capacity for mutation, which makes them highly adaptable and changeable
The size of most viruses is so small that they cannot be seen through a light microscope, although there are exceptions such as large viruses (called gyrus ) whose size is exceptional.
Although viruses are enormously diverse in their shape and structure, they are typically about 100 times smaller than bacteria and consist of a DNA molecule wrapped in a protein capsule . There are four possible forms of viruses:
The virus reproduction process comprises various stages and takes place within the infected organism and specifically within certain types of cells (infectious selectivity). These stages are:
Several types of viruses have been identified according to the type of genetic material they possess and the replication method they use inside the cell:
Viruses have a relatively short lifespan , since their entire existence is devoted to identifying and infecting suitable cells. However, viral infections can be transient or chronic, curable or fulminant.
Diseases caused by viruses in man are abundant. They oscillate between temporary infections, which last as long as it takes for the immune system to control the presence of the virus and expel it from the body, and others that require treatment to eliminate or at least control the infection.
Throughout history there have been numerous pandemics of viral origin that have cost numerous human lives, such as chickenpox, Ebola, dengue or chikungunya fever .
Viral transmission depends largely on the type of disease in question, and can be spread from one healthy individual to another , directly, through the exchange of fluids (sexual contact, blood transfusions or even through coughing and direct contact with infected skin); or indirectly, through an intermediary (a mosquito , a flea, an animal bite, etc.).
Since viruses do not respond to antibiotics , in many cases the only possible treatment is rest and treating symptoms to avoid further complications. In other more severe cases, the viral infection requires medical treatment with retrovirals . Some viral infections cannot be cured outright, but rather kept at bay, at levels that are not dangerous and infective.
Many viruses can be used by human technology for a variety of purposes , ranging from pest control, biological weapons, or biological actors in the medical industry and nanotechnology. This is because they are relatively simple organisms, which can be engineered through laboratory-assisted evolution.
There is debate as to whether or not viruses are living things since they possess life-like characteristics (such as genetic material) and are dependent on living cells to synthesize their proteins, but they differ from even the most primitive bacteria in that they are infinitely simpler.
Furthermore, the logic of known life is based on the minimum unit of the cell, and viruses are not composed of them. That is why it is accepted that they are beings on the margins of life.
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