1. Introduction: Medical Virology Akram Astani Department of Microbiology University of Yazd

2. Basics of Virology VIRUSES?

3. First document of a virus infection Ruma 1.500 B.C.

4.  1882 A. Mayer: transmission of tobacco mosaic disease by plant extract; pathogen can not be isolated  1892 D. Ivanofsky: agent of tobacco-mosaic disease is ‚non filtratable‘ and can not be propagated in culture medium  1898 M. Beijerinck: the pathogen can be propagated in live tissue The pathogen is: ultrafiltratable does not replicate outside of live tissue ultravisible ‚Contagium vivum fluidum‘; later Virus (lat. poison) History of Virology: discovery of viruses

5.  1898: Loeffler and Frosch; foot and mouth disease virus (1. animal virus)  1901: W. Reed; yellow fever virus (first human virus)  1911: first discovery of a tumor virus (Rous Sarcoma Virus)  1915: discovery of bacteriophages (Twort; d‘Herelle)  1935: Crystallization of TMV (Stanley)  1949: propagation of Polio virus (Enders, Weller, Robbins)  1970: discovery of reverse Transcriptase (Baltimore, Temin)  1977: Last case of pox (Somalia)  1983: discovery of HIV History of virology: some important milestones Peyton Rous

6. Leading causes of death in 2008 (World Health Report): Medical importance of viral diseases WorldDeaths in millions% of deaths Ischaemic heart disease7.2512.8% Stroke and other cerebrovascular disease6.1510.8% Lower respiratory infections3.46(Influenza) 6.1% Chronic obstructive pulmonary disease3.285.8% Diarrhoeal diseases2.46(Rotavirus) 4.3% HIV/AIDS1.78(Africa: 20%) 3.1% Trachea, bronchus, lung cancers1.392.4% Tuberculosis1.342.4% Diabetes mellitus1.262.2% Road traffic accidents1.212.1% Measles: 1.4% (2000)

7. Two theories of viral origin can be summarized as follows: May be derived from DNA or RNA nucleic acid components of host cells may be degenerate forms of intracellular parasites. Viral origin

8. Differences between viruses and bacteria con. bacteria rickettsia chlamydia viruses Obligat. Intracell.-++ + Nucleic acid DNA and RNA DNA and RNA DNA and RNADNA or RNA Protein synthesis+++ - Energy metabolism++- - Replication cell division cell division cell division Assembly Sensitivity towards antibiotics+++ - CHLAMYDIA: Obligate intracellular bacterial parasite which depends on eucaryotic cell for energy.

9. ‚Frontiers‘ of Virology Viroid Virosoids Prion genome circular RNA ss RNA - hosts plant plant, human human, animal ExampleCoconut *Hepatitis D Virus Kuru Cadang Cadang * Need a helper virus (HBV) to replicate