Viruses are the smallest organism, it is difficult to think of them as living because they can only ‘live’ inside another living cell. They do not have a normal cell structure like any other organism. Billions of viruses ‘exist’ around us – it is only when they enter the cells of other organism that they show some of the characteristics of life. There they can reproduce and grow in numbers.
Viruses that attack bacteria are called bacteriophages are simply phages. The phages DNA is infected into the bacterium where it makes 20 : 1000 copies of itself which are released to infect further bacteria.
Viruses have a great impact on life and earth because they can live in every type of living organism, from bacteria to plant to animals. It is evident, that they have change the course of human history because of diseases such as : small pox, measles, AIDs, Middle East Respiratory Syndrome,(MERS-Cov) and Severe Acute Respiratory Syndrome (SARS-Cov) , Coronavirus disease (COVID19) caused by the coronovirus. A novel coronavirus (nCov) is a new strain that has not been previously identified in humans.