Viruses are beings that don't have cells, are made up of nucleic acid which may be the DNA or the RNA, surrounded by a protein envelope called capsid. They are about 0.1µm in diameter, with dimensions only observable under the electron microscope.
Because they are so small they can invade cells, including unicellular organisms such as bacteria. It is by parasitizing cells of other organisms that viruses can reproduce. As they are obligatory parasites, they cause parasitized diseases called viruses.
Viruses have very different forms of organism, but all have a capsule made of protein, where is the genetic material of these beings. This genetic material undergoes modifications, ie mutations, often leading to the emergence of varieties (subtypes) of the same virus. This makes it difficult to combat and compromises the effectiveness of various vaccines, which are prepared to combat specific types of microorganism. The ability to suffer genetic mutations It is one of the characteristics that viruses have in common with living things.
Viruses can only be viewed with the aid of electron microscopes, instruments available only in specialized locations, such as research centers, universities and large laboratories, which can show enlarged images up to hundreds of thousands of times.
Image of an electron microscope showing the HIV virus, circular format.
Viruses and health
The word virus has Latin origin and means "poison". Probably this name was given due to viruses, which are diseases caused by viruses.
Our body has natural defenses like antibodies, which are proteins produced by special blood cells against disease-causing agents. Fever itself is a mechanism to fight infections, as rising temperatures activate metabolism and accelerate the reaction of white blood cells. When the axillary temperature exceeds 37.5 degrees Celcius, however, the person should be treated by the doctor. In addition, we have products such as vaccines, serums and some antiviral medicines (not to be confused with antibiotics).
Viruses generally cause malaise, pain, and fever, but each virus has its own symptoms and can be more or less severe.
Each type of virus "attacks" specific cells. The mumps virus, for example, parasites the salivary or parotid gland cells, causing swelling and pain in the sides of the neck.
In some diseases, including certain viruses, transmission depends on the action of a vector. This term refers to the being that does not itself cause disease in other beings, but carries in its body the causative agent and can transmit it. As an example, we have certain species of mosquito that transmit viruses by biting sick individuals and then healthy individuals, spreading the disease.
Currently approximately 3,600 species of viruses have been identified, which can infect bacteria, plants and animals, as well as settle and cause disease in humans. Each disease with particularities as to the mode of transmission, characteristics of the infection and prophylactic measures.
The viral diseases that most affect the human body are as follows: Flu, Chicken Pox or Chickenpox, Mumps, Dengue, Yellow Fever, Hepatitis, Rubella, Measles, Smallpox, Herpes Simplex and Rabies.
The proteins that make up the virus capsules are different from the proteins in the human body. When we are infected by viruses, the proteins of these beings - "foreign" to our bodies - are "detected" by certain cells in the body. These cells are part of the immune system, which is the body's defense system, and then produce substances that fight the invading virus: antibodies.
When someone gets a cold, for example, the immune system starts producing antibodies. After a few days, the antibodies eliminate the viruses and the person is healed from the cold.
Antibodies have specific action. This means that they only act in the fight against the microorganism for which they were produced. In the previous example, the antibody capable of reacting to the cold virus does not fight the measles virus, and vice versa.