VIRUSES And PRIONS

STRUCTURE DNA strand or RNA strand Covered by a Capsid Capsid (protein covering)

Infection and Reproduction DNA or RNA -into host DNA Uses host proteins (enzymes, etc.) to reproduce Once reproduced to a certain level – burst (lyse) & infects other cells Capsid (covering) – identify host to attach and enter cells Capsid – also is portion that immune system identifies to attack the virus.

HOSTS required to reproduce All organisms may be hosts Usually specific hosts

Cycles Lytic Cycle –lyse cells shortly after infection influenza, HPV Lysogenic Cycle- remain dormant (“hidden”) in the cell - a trigger causes the viruses to begin growing and move to 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 Some 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

Immune Response Antigenic (protein) surface markers on capsid cause an immune response Immune system produces antibodies to attack the infection. Memory: If re-infected the immune system remembers the antigen & will attack the virus before you get sick.

Edward Jenner and Vaccinations milk maids had immunity to smallpox Hypothesis: Milkmaids exposed to a less virulent (dangerous) form of the virus (cowpox) have immunity to smallpox. injected a boy with cowpox- the boy got sick but recovered. then injected the boy with smallpox – the boy did not get sick!

How vaccines work (memory) Vacca- Latin for cow agent that resembles the disease-causing microbe immune response – if exposed to virus the immune system remembers it and destroys the virus before the host gets sick.

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

Definitions Endemic –regularly found in a population Epidemic -widespread occurrence at a certain time. Pandemic - world. Virulence /pathogenicity– severity epi = on, upon, above Demic – relating to people or district Pan=all En= within

Definitions Vector –(carrier) 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 Spanish flu Killed > Great War or World War I 38 million from WWI/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