Viral comes from the word virus. We have heard the word virus long time ago . We know virus is a Latin word for poison.This is the name of a large class of protein substances they are only visible by the electron microscope. They are lifeless until they come into contact with the right cells of a living organism. It triggers into a reproductive activity. This produces the frequently epidemic diseases such as the common cold,influenza,small pox etc.
The deadliest disease is small pox, it can wipe out a community. Vaccines are invented to combat the disease. The World health Organization declared in 1979 that the disease is eradicated. The threat since then is from existing samples of the virus at two research locations, One in the U.S and the other in Russia.