Each Viral Infection Has Its Specific Symptoms

Some time ago one of most terrible diseases was considered natural smallpox, virus of which may live only in human body. During two decades in the world there were registered no cases of infecting human with natural smallpox, it means that the virus causing the disease ceased to exist in wild life. This occurred due to compulsory vaccination against smallpox in past.

Before 1958 each year in the world the diagnosis “smallpox” was made at average 250,000 times. In 1958 the WHO started the campaign of total smallpox liquidation. In 1980 was declared that the Earth is free of natural smallpox.

Each cell in the body performs a number of specific individual functions. After infecting with virus sooner or later do appear problems. Virus damages liver cells – this causes yellow disease and other signs of liver failure. Virus damages mucosa of bronchi – this causes cough, rhonchi in lungs and hurried breathing.

Virus enters cells of the brain – do appear disorder of consciousness, cramps, paralysis. Selectivity of viruses leads to the fact that each viral infection has its specific symptoms and the symptoms will be determined by inability of group of cells damaged by viruses to perform their functions.

Severity of viral infection depends on what cells and how many of them are damaged. It is clear that damage of brain leads to more serious illness than damage of cells of nasal mucosa.

Every cell in human body changes in a certain way during its growth and development. It means that liver cell of a child is not the same as liver cell of an adult. In a child hepatic cell is not maturated yet and hepatitis A virus can hardly multiply in these immature cells, therefore one-year-child never gets diseased with hepatitis A, in older children the disease courses mildly, in teenagers severely than in children, in adults it courses severe.

Childhood infection (rubeola, chickenpox) do course severe in adults. The severity of disease is determined by the condition of a particular cell. For example, hepatic cell of a drunker is weaker than in a non-drunker.

The Variety Of Viruses

 Virus may be seen only with the help of electronic microscope. The vast majority of doctors meet viruses and electronic microscopes only on images in clever medical books. Diseases caused by viruses  have so specific symptoms that it makes no use of  electronic microscope and images because everything is clear.

The essential and most significant biological peculiarity of any virus is that it is unable to multiply without cells of other organisms. Virus enters a particular cell and this infected cell transforms into a factory of virus production.

It is clear that cell cannot work for both virus and body and thus it cannot perform its major function and here appear absolutely specific symptoms of the disease. Major feature of the virus is its selectivity. Virus cannot live in any cell, it needs a proper one which will work for it.

For example, infectious hepatitis virus may live and multiply only in liver cells. Epidemic parotitis virus (mumps) prefers cells of salivary gland, influenza virus – cells of mucous membrane of bronchi and tracheae, encephalitis virus – cells of cerebrum. Each virus may be associated with particular cells and tissues of human body which virus damages.

Virus selectivity is observed not only in damages of particular cells but also in the ability to cause particular diseases in particular biologic species. Measles virus may find necessary cells in human body and is not dangerous for a cat. Virus of hardpad is not dangerous for a human.

These are not common rules. Particular cells of different mammals are analogous with each other and some viruses cause one and the same disease in different animals, for example, rabies virus. The ability of some viruses to affect only particular biological species has a great significance.