Virus is an infectious agent that replicates inside a living organism. A virus can infect all types of living organisms from, human, plants, animals to archaea and bacteria. Viruses can be found in almost every type bionetwork on earth and are most extensive biological unit. Virology is the study of viruses, and a subspecialty of microbiology. More than five thousand types of viruses have been described, and there are millions of others. Viruses are not living organisms because they are simply DNA pieces, which ...