1
The Case for Evolutionary Thinking
(The Evolution of Virulence)
Questions to consider from Chapter 1.
1) Why are promising AIDS treatments, like the drug (AZT) proven ineffective in the long run?
2) Why are some people resistant to becoming infected or to progressing to disease status once they
are infected?
3) Why does HIV kill people?
4) Could a vaccine provide protection from the diversity of HIV strains found today?
HIV – Human immunodeficiency virus
AIDS – acquired immune deficiency syndrome
I. Where Does HIV come from?
A. The notoriety of HIV and AIDS. Caused more deaths than the Black Plague.
a. At the end of 2002, 42 million people were living with HIV/AIDS (50 5 women) [Science. Vol.
298, 2003 –70 million people.]
b. Total deaths due to HIV / AIDS as of end 2001 24.8 million. (American Medical Student
Association) [Science. Vol. 298, 2003 –20+ million people.]
B. Two distinct epidemics (comparative epidemiology) that occurred during the 1980-1990s.
a. One in sub-Sahara Africa. Transmitted mostly via heterosexual intercourse.
b. The second occurred in North America and Europe and is transmitted among homosexuals and
needle sharing among intravenous drug users.
II. What is HIV? HIV is a virus. Is it alive? That is, is it considered living?
“A virus is a piece of bad news wrapped in protein” – Sir Peter Medawar.
A. How it operates see pp. 5-6 in Freeman & Herron.
1) HIV is a “retrovirus” because flow of genetic information is backwards.
RNA DNA mRNA protein (instead of DNA RNA protein)
2) Why is an illness due to virus not treatable with antibiotics?
B. Consequences for the host – How does it cause AIDS?
The human body has two courses of action for dealing with viruses.
1) Destroy virions that are traveling in the blood stream.
2) Kill its own infected cells.
3) Because the type of cells attacked are the very ones that the body would use to fight the virus,
HIV hits the body with a double whammy. The immune system becomes severely
compromised.
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