A virus is a microorganism that is not visible to the naked eye. It is highly contagious and communicable. A virus attacks and clips to a living cell of the human body. It then discharges its DNA or RNA, which smashes the original genetic material and functioning of the cell. But before the victimized cell expires, it leaves or releases more of that virus. The virus multiplied in such a fashion impedes the growth and working of other healthy cells too, so much so that sooner or later the entire body comes in its grips. However, the immune system of the body endeavours its best to brawl the viral attack. But it does not succeed in all the cases. Due to this reason, the doctors and dieticians prescribe a healthy diet rich in nutrition that strengthens the resistance of the body.
The Residence and Transmission of Virus- there are different types of viruses known. Some infect humans, others animals and a few affect both. Viruses are everywhere in our surroundings. They can be transmitted via the food we eat, air we breathe, water we drink, sexual contact etc.

Some common Viral Infections- there are some well known viruses and the diseases caused by them.
HIV virus is one that destroys the cells in the immune system of our body. It is therefore named as HIV i.e. Human Immunodeficiency Virus. HIV takes the form of AIDS at an advanced later stage. HIV virus reaches the human body through several ways such as- via sex with a partner who is already living with HIV, though infected mothers milk to her child, through human saliva, HIV contaminated needles, syringes and so forth.
Thus, one should be very cautious regarding all these factors. Completely safety should be observed to avert lifelong HIV infection especially because no adequate cure is yet available to eliminate the effect of HIV.

Hepatitis is even caused by virus. Since different kinds of viruses are at work, there are different types of hepatitis. These viruses harm the human liver, which results in its burning or inflammation.
Hepatitis A and E spread via the food and water of the infected person and through anal sex. There exists a vaccine for hepatitis A but not for E. Hepatitis B is caused by unprotected sex, childbirth and contact with infected person. Vaccination is available for hepatitis B and it is better nowadays to get vaccinated against it. This sterilization also ceases the threat to be caught by hepatitis D in future. Hepatitis C virus is transferred by the way of contaminated blood and is cured through medicines. A possible prevention to hepatitis is to maintain hygiene and vigilance in matters of sex and contacts with other persons.

Viruses are a very common type of infectious disease. Many of the most common human diseases are viral. Viruses are the smallest pathogens known, made of genetic material surrounded by protein capsid.

Common viral infections may be diagnosed based on symptoms. For infections that occur in epidemics (such as influenza), the presence of other similar cases may help doctors identify a particular infection. For other infections, blood tests and cultures (growing microorganisms in the laboratory from samples of blood, body fluid, or other material taken from an infected area) may be done. Blood may be tested for antibodies to viruses or for antigens (proteins on or in viruses that trigger the body's defenses).