Viruses: Friend or Foe (3/10/2008 lecture)

Today - focus on traditional bad viruses
Wednesday - more-positive uses of viruses
Long bad history

Egypt - withered legs (from polio?), smallpox lesions
Homer (the old Greek one, not the Simpsons one) discussed rabid dogs

Viruses have reshaped human history
Smallpox - major tactical advantage Europeans had vs. Native Americans
Influenza - post-WWI not the only major epidemic
Polio
HIV

-Role of biological warfare-

Smallpox - very contagious - psutiles of smallpox victims burst to spread lots more of the virus
Smallpox - only infects humans
Declared eradication in 1977

Influenza - smaller particles than smallpox virus
Influenza epidemics - a lot of them, but post-WWI was the worst - 20,000,000 dead (double WWI combat deaths)
1920 epidemic hit mostly the very young and very old, but also deaths inbetween,hich was shocking

Polio - FDR's suffering form the disease galvanized response
Polio often causes paralysis. Iron lung necessary if diaphragm suffers from the paralysis

Polio epidemic in 1952 - side-effect of cleaner society (less mild immunities built up)

HIV-AIDs - Misunderstood in the beginning, misunderstanding-based public fears
Africa being hit especially hard

Polio elimination followed smallpox. Polio endemic area reduced to India and parts of Africa

Chicken v. Egg - viruses or bacteria?
Were virus-like things the first replicators? Modern virii need cells to replicate, did the ancient
ones?

Okay, some bad things that viruses have done.
Now what are they?

They are very very small (20-400 nanometers)
DNA or RNA in genome
Protein shell
Some, such as HIV, have a lipid (fat) envelope
*obligate intracellular parasites*

Different viruses can affect all different types of organisms (any of the other phyla)
Filterable if you can do a filter small enough