VIRUSES And PRIONS

STRUCTURE A core nucleic acid (A,T,C, and Gs - DNA or RNA (U) Nucleic Acid surrounded by a protein, called a capsid.

CLASSIFICATION By genomes: DNA viruses, RNA viruses or retroviruses (any of a group of RNA viruses that insert a DNA copy of their genome into the host cell in order to replicate, e.g., HIV.)

Evolution of Viruses Two theories: Evolved from bits of exogenous (escaped) from genes of larger organisms - dead bacteria? Evolved from complex molecules proteins and nucleic acids before cells first appeared on earth Coevolution between viruses and other organisms (can be mutualistic, parasitic, or commensal)-

HOSTS required for viral reproduction All types of organisms are hosts. - bacteria, fungi, humans, cows, bats, sheep, sponges, plants, etc. Enter the host cell because capsid markers adhere to receptor cells of host Highjack the host DNA and reproduce

Ebola Virus Electron micrograph of Avian Flu Virus

Cycles of Viruses Lytic Cycle – infect, reproduce, and lyse (break-open the cell) – influenza, HPV Lysogenic Cycle- infect, remain dormant (“hidden”) in the cell, a trigger will cause the viruses to begin growing and go through the lytic cycle (bursting) to release more viral particles. (Shingles, HIV) Amoeba Sisters Summary https://s-media-cache-ak0.pinimg.com/originals/e2/0f/50/e20f508e9c5a5fcd5eb7d02f0600c823.jpg

VIRUSES CAN BE BAD or DEADLY Smallpox – viral infection 20-60% fatality rate overall 80% in children Responsible for 300-500 million deaths during the early 20th century Eradicated in 1979 (Somalia)

Immune Response Antigenic (protein) markers on capsid of the virus cause the immune system to react. Immune system produces antibodies to attack the infection. Once exposed, the immune system remembers the antigen – re-exposure will attack the virus before knowing you are sick

Edward Jenner and Vaccinations Noticed milk maids had immunity to smallpox Milkmaids were exposed to a less virulent (dangerous) form of the virus (cowpox) Edward Jenner inoculated a boy with cowpox- the boy got sick, but recovered. He then inoculated the boy with smallpox – the boy did not get sick! Beginning of modern day vaccinations

What is a Vaccine Biological agent-improves immunity to a specific agent Vacca- Latin for cow Contains an agent that resembles the disease-causing microbe Similar pathogen (cowpox for smallpox) Killed virus (polio) Weakened virus (measles, mumps) Toxin (usually bacterial- diphtheria)

1918 Flu Pandemic I had a little bird its name was Enza I opened the window And in-flu-enza -poem 1918

Definitions Endemic – disease regularly found in a population Epidemic -a widespread occurrence of an infectious disease in a community at a particular time. Pandemic - whole country or the world. Virulence or pathogenicity– severity of a disease (for viruses: a. Speed of replication, b. ability to enter the host cell, ability to evade the host immune system, ability to lyse the cell) epi = on, upon, above Demic – relating to people or district Pan=all En= within

Definitions Continued Vector -an organism that transmits a disease or parasite Reservoir (disease) – host- infectious agent normally lives and multiplies Zoonotic Infections- disease that can be transmitted from animals to people  (rabies, SARS, influenza, Lyme disease)

1918 Flu Pandemic (Spanish flu) Killed more people than the Great War or World War I 38 million from WWI and approximately 50 million from 1918 flu 1/3 of the World Population Infected (500 million Normally influenza has a 0.1% fatality rate, but 1918 had increased virulence because of new mutations- all those that may have been immune with a slight mutation were not. Economic impacts and impacts to the war effort

Prions protein particle transmissible spongiform encephalopathies (TSE) which -neurodegenerative diseases. Most commonly known- Mad Cow Disease, Scrapie, CJD, Kuru Ceph- head – https://www.youtube.com/watch?v=ujK7KiLt0s8

Virus or Prion Project 20 points - Creation of a colorful, neat, presentation, poster, essay, or movie about a virus. Name of the Virus or prion – both common and scientific, if applicable, (chicken pox - varicella-zoster virus  Picture of the virus or prion Genome of the virus (RNA or DNA or protein if a prion) Epidemiology of the Virus or prion (reservoir(s), vectors, spreading, fatality rate, risk factors etc.) Mention any outbreaks of the viral disease with historical implications Portion of the body infected. Symptoms of infection Preventions of infection Treatments of infection 20 points -