Viruses are microscopic infectious agents, and up to 10,000 smaller than most bacteria. They are the most common biological structure on our planet, being more numerous than animals, plants, fungi, parasites and bacteria together.
Not all viruses exist that are capable of penetrating the human body. Likewise, not all viruses present in the body are able to cause diseases. Often a plant capable of infecting virus or bacteria is completely harmless to humans. The reverse is also possible, such as smallpox virus that is capable of infecting human, but not other living beings.
There are about 21 families of viruses capable of causing diseases in humans. The same family may be responsible for several different diseases, as is the case of the family Herpesviridae, comprising more than 130 types of viruses which may cause herpes simplex, chickenpox, herpes zoster, mononucleosis, Kaposi's sarcoma, sudden exanthema, cytomegalovirus, etc.
In this article we will explain quickly and briefly what is a virus, as it causes damage to humans and which are the main diseases of viral origin.
For most of the scientific community, viruses are not considered living beings. In fact, it is a hybrid between living and non-living things, because it has characteristics of both. The justification for not consider it a living being comes from the fact that the virus does not possess cellular characteristics, are unable to produce their own energy, not grow, not divide and are completely inert in the environment. A virus is basically a small collection of genetic material (DNA or RNA) wrapped in a protein capsule.
For the virus shows any sign of activity and play, it must be within the cell of a living being. Therefore, it is considered an obligate intracellular parasite. Out of intracellular, one virus is an inanimate structure.
For the virus to be able to multiply and cause disease it is essential that it can penetrate into any cell in our body. This process is not always simple.
Our cells have on their surface molecules that act as a kind of lock. For any structure that can cross the cell wall is necessary to have a "key" that combines with the "lock" on the surface of the cell. Cells expressing different "locks" different.
Human papillomavirus structure
So for a virus able to achieve within a given cell, it needs to present on its surface a molecule that serves as a "key" to the "lock" that cell. Viruses have several molecules on their surface which act as a "key" as can be seen in the illustration above. If our body does not exist a cell with a "lock" compatible with one of the "keys" that the virus has, it will enter our body, can not penetrate any cell and will be easily removed by the immune system.
This explains why some viruses are incapable of infecting human, being restricted to plants or animals. This same analogy explains why some viruses only cause respiratory infections while others only attack the gastrointestinal system, liver or nervous system. Thus, we can conclude that the virus does not attack the cells he want, they only attack the cells it can.
Viruses are structures with a single function: to reproduce.
Once inside the cell, the viral genetic material (DNA or RNA) is released and mixes genetic material of the cell that hosts it. As a result, the host cell begins to receive orders from the viral genes in order to replicate virus proteins, such as a photocopier. What the virus does, therefore, it is to take advantage of the organelles in cells to produce thousands of copies. A single virus can lead to millions of its clones.
When the immune system detects the presence of a cell "sequestered" by a virus, it destroys, preventing it to continue to replicate the invading agent. Now imagine you with thousands of infected cells and your immune system acting desperately, causing cell verdeiro genocide, releasing large amounts of enzymes, cytokines, hormones, etc. That's why we feel bad when a virus attacks us. Symptoms of a viral disease are caused not only by cell function change induced by the virus, but mainly by the immune system's response to invaders.
One of the main ways of defending the body against viruses is a substance called interferon. When a cell is invaded by a virus, it starts to produce interferon, which acts warning other cells of the existence of the invading germ. Interferon, in addition to alerting the defense cells under the presence of a virus also causes the not yet infected cells in the body become more difficult to be invaded by millions of new virus produced.
Interferon is a very important substance for our protection, however, he is responsible for several typical symptoms of viral diseases, such as fatigue, malaise, drowsiness, fever, body aches, chills, etc.
There are countless diseases caused by viruses. Let's quote some of them now. If you want more detailed information about the diseases listed below, visit the link that will be next to each.
Influenza: caused by influenza virus causes respiratory tract symptoms. There are several types of flu and influenza, such as influenza A (H1N1) and avian influenza (H5N1).
Cold: caused by many different viruses, including, parainfluenza, rhinovirus, adenovirus and coronavirus. It also causes respiratory tract symptoms.
Infectious mononucleosis: Caused by the Epstein-Barr virus causes sore throat, fever and increased nodes in the neck.
Viral pneumonia: caused by many different viruses, including, influenza, parainfluenza, respiratory syncytial virus, Adenovirus, Coronavirus and hantavirus causes the pulmonary infection.
Viral gastroenteritis: caused by several different viruses, including, Rotavirus, Norovirus, Enteric adenovirus and Astrovirus, causes diarrhea and vomiting frame.
Viral conjunctivitis: mainly caused by adenovirus, causes red eyes, itchy and watery eyes.
Genital herpes: caused by herpes simplex virus 2, it is an STD that causes sores in the genital area.
Varicella (chickenpox): caused by the Varicella-zoster virus, causes fever and rash.
Herpes zoster: also caused by the Varicella-zoster virus causes painful blisters on the skin.
Rubella: caused by the rubella virus causes fever and rash.
Measles: caused by measles virus also causes fever and skin rashes.
Mumps (infectious parotitis): caused by the mumps virus causes fever and swelling of the parotid glands.
Smallpox: caused by the variola virus, a disease is eradicated from the 1970s, which caused skin rashes.
Dengue: caused by the dengue virus and transmitted by the mosquito Aedes aegypti , causes fever, eye pain and body aches.
Yellow fever: caused by the yellow fever virus is also transmitted by mosquitoes and causes fever, chills and body aches.
Chikungunya fever: caused by the Chikungunya (CHIKV) virus causes a very similar picture with dengue also being transmitted by the same mosquito Aedes aegypti.
AIDS (HIV): caused by the human immunodeficiency virus (HIV) is a STD that leads to destruction of the immune system.
Cervical cancer: caused by some sub - types of human papillomavirus (HPV), which is a sexually transmitted virus.
Viral hepatitis: Caused by different types of viruses, causes different types of hepatitis, such as hepatitis A, hepatitis B and hepatitis C.
Poliomyelitis: caused by the polio virus, it is a virus that can attack the nervous system, causing paralysis.
Human rabies: caused by rabies virus is a disease of high mortality, transmitted by animal bites and causes serious damage to the central nervous system.
Hand-foot-mouth syndrome: hand-foot-mouth syndrome (SMPB), also called hand-foot-mouth disease is a common contagious viral infection in children, which is characterized by small sores in the mouth and rashes the hands and feet.
Cytomegalovirus: caused by cytomegalovirus, causes mononucleosis like frame, with fever and swollen lymph nodes.
