What are Viruses? How do they infect organisms?

Microscopic Picture of Polio Virus
From fever to AIDS, viruses are the propagators of most of the diseases in the world today. A virus is a pathogen that causes disease in its host. Viruses are smaller than the bacteria and can infect all kinds of organisms including bacteria. The usual viruses are sized between 20 and 300 nanometres. The part of virus that causes the disease is called Virion. The primary part of Virion is a nucleic acid with a coating of protein. The nucleic acid could be either DNA or RNA. The protein coating is called Capsid and the nucleic acid with the coat is called Nucleo Capsid. Capsid is the part that gets attached to the host cells and forces the viral genomes into them. There are millions of types of viruses. The study of viruses is called Virology.
The structure of the viruses differs according to the groups. The most common structure is spherical shape. There are viruses in the forms of rods and hexagons as well. Bacteriophages, the viruses which infect bacteria, are among those with highly complicated structure.
According to the nucleic acid contained in them, the viruses are classified into two groups. Those with RNA are called Ribo Viruses and those with DNA are called De Oxy Ribo Viruses.
The nomenclature and classification of the viruses are supervised by International Committee on Taxonomy of Viruses. The more acute classifications are done according to the structure of the nucleic acid, the size of virion and the number of capsomere.
Even though, they show life properties viruses are more like living chemicals. They don’t have cells or nuclei like living organisms. They can only live depending on the host cells and will be dormant outside the cells. Due to this feature, they can be kept for any amount of time in this state.
Viruses are spread in numerous ways including insects, blood and sexual contact. When the nucleic acid of a virus gets inside the host cell, they begin to multiply there and build a new protein coating. They would use the energy of the host cells for this process and it eventually results in the damage of the cell. Once the host cell is damaged, the virus exits and begins to attack the neighbouring cells as well.
The viruses will be inactive in the presence of sunlight and ultraviolet rays. They are, however, more resistant to chemicals than bacteria. They can’t be killed by antibiotics either. Vaccines are the best way to prevent the viral infection.

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