Basics about Viruses and History of Viruses

What is a Virus? A virus is a non-living infectious pathogen A virus contains either DNA or RNA and virtually, nothing else A virus has a protein coat A virus has special receptors on the protein coat that allow it to be seen as a “self” cell to a host cell A virus can cause immediate illness, or act as a transposon and jump into the host DNA and sit until later. A virus can cause cancer

Viruses—Examples O’Nyong-NyongHepatitisRabiesPolioHIVRotaSindbisNorwalkCaliciLassaDengueMarburgYellow-FeverRubellaMumpsMeaslesHantaanEpstein-BarrCowpoxInfluenzaEbolaOMSKJuninDuvenhageOropoucheORFCoxsackieChikungunyaBunyamweraHerpes

Anatomy of a Virus A bacteriophage only Invades bacteria. The Most famous is the T4, which invades E.coli bacteria.

Retroviruses: have two strands of RNA. In order to reproduce, they need reverse transcriptase (a protein), which takes their RNA, makes DNA, then makes more RNA.

Animal Viruses Can be single or double DNA or single RNA strand viruses. Animal viruses take over the nucleus of a host cell. This is the influenza virus in a human cell during infection, replication, and transmission.

Infectious Diseases Throughout History Infectious agents have probably always caused disease in humans. Smallpox has been described in ancient Egyptian and Chinese writings and may have been responsible for more deaths than all other infectious diseases combined. There is evidence that malaria and poliomyelitis have existed since ancient times. In the 14 th Century, the bubonic plague, or Black Death, killed about 20 million people in Europe alone. In the 20 th Century, the 1918 influenza may have killed up to 50 million people worldwide Close to 20 million people have died of AIDS to date. Courtesy of CDC Recreated 1918 Influenza virions. The 1918 Spanish flu killed more than 500,000 people in the United States and up to 50 million worldwide.

History of Viral infections heiroglyphs from Memphis, the capital of ancient Egypt, drawn in approximately 3700BC, which depicts a temple priest called Ruma showing typical clinical signs of paralytic poliomyelitis. The Pharaoh Siptah ruled Egypt from BC when he died suddenly at the age of about 20. The mummy shows that his left leg was withered and his foot was rigidly extended like a horse's hoof - classic paralytic poliomyelitis.

The tobacco Mosiac Virus was found on the 12th February 1892 by Dmitri Iwanowsk ( ), a Russian botanist. The Pharoh Ramses V, who died in 1196BC, is believed to have succumbed to smallpox- note the pustular lesions on the face of the mummy.

Viruses—History Invasions, wars, and immigrations can introduce viral diseases to different populations Some viral infections have had major global effects: –Influenza type A is believed to be responsible for global flu outbreaks in 1918, 1957 and th century Spanish explorers brought small pox, measles and influenza viruses to the New World P22

History of Vaccinations On 14th May 1796, Edward Jenner used cowpox-infected material obtained from the hand of a milkmaid from his home village of Berkley in Gloucestershire to successfully vaccinate 8 year old James Phipps, on 1st July He deliberately inoculated him with material from a real case of smallpox ! Cowpox is related to smallpox- luckily this vaccination worked.

Reducing the Spread of Infectious Diseases Vaccines Antimicrobial drugs and soaps Good personal hygiene and sanitation Protection against mosquitoes Quarantine Anti-viral drugs like tamiflue