Notes

about a century ago at the time of louis pasteur and robert koch the word virus was generally associated with poison associated with disease and death.the presnt notion of virus is entirely different .viruse are recognized as particles of nucleic acids often with protein coat .they replicate ij living cells and cause many diseases such as influenza hepatitis aids and small pox .bacterial viruses are known as bacteriobenphages .the branch which deals with the stdy of viruses is known as virology.
the word viruse is derived from the latin word venome meaning poisonous fliuid .it ise defined as non cellular infectious entities which contain either rna or dna normally encased in a proteinaceous case .that reproduce inly in living cells .viruses use the biosynthetic machiney of host for its own synthesis and then transfer themselves efficiently to other cells.
some viral diseases have identified for centuries .in fact the first infectious disease against which effictive method of prevention is used was a viral disease.in 1796 Edward Jenner first vaccinated an 8 years old boy with material removed from cowpox lesions on the hand of milk maid .after six weeks the boy was inoculated with pus from small pox victim but he did not develop the disease .late on Jenner used the material for vaccination from cowpox lesions and successfully vaccinated 23 people.as the material he used from obtained from cow latin vacca later on the term vaccination was used by the louis pasteur for the inoculation against diseases.