BICD 2014. 9. 17.¢  A good scientist, like a good detective, uses his or her judgment. Not all possibilities

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  • BICD 136! AIDS, Science & Society! Prof. Hedrick! WLH 2001! Final 7-10 pm Friday, December 19, 2014! Class Website: http://hedrick.ucsd.edu/BICD136! Film password: SH136! Section !Instructor ! ! !Opt!Author !Title !! 818124 !Hedrick, Stephen M !HR !Shilts !And The Band Played On! !Hedrick, Stephen M !R !Parham !The immune system!

    ! ! ! ! ! ! !R !Stine !AIDS Update!

    An introduction to all aspects of the AIDS epidemic. Topics will include the epidemiology, biology, and clinical aspects of HIV infection, HIV testing, education and approaches to therapy, and the social, political, and legal impacts of AIDS on the individual and society. !

  • AIDS, Science & Society!

  • HIV epidemic! HIV is a lentivirus, a type of retrovirus that came from chimpanzees and developed into a human pathogen in the last century It will never leave the human species It kills a type T cell that is essential to many aspects of the adaptive immune system As these T cells are diminished, the human body is unable to manage environmental microbes and viruses. Death is inevitable Victims die of multiple infections HIV has killed at least 30 million people thus far

    Deaths in 2011: ~1.7 million With the advent of Highly effective anti- retroviral drugs, people can remain relatively healthy

  • Lecture 1! Epidemiology and HIV!

    Great fleas have little fleas upon their backs to bite 'em, And little fleas have lesser fleas, and so ad infinitum. And the great fleas themselves, in turn, have greater fleas to go on; While these again have greater still, and greater still, and so on Augustus De Morgan Budget of Paradoxes-1872

    Epidemiology, why are some diseases successful (widespread), whereas other’s die out. Why are some highly virulent (even lethal), whereas others are benign? What prevents an infectious agent from wiping out a entire species? What evolutionary pressures guide these interactions? Where does HIV-AIDS fit into these concepts?

  • AIDS in Brief !

    •  Caused by the Human Immunodeficiency virus (HIV).! •  Characterized by severe damage to the immune system.! •  An important clue was the development of a lung

    infection (or pneumonia) caused by a fungus called Pneumocystis in AIDs patients.!

  • What is epistemology?! The theory of knowledge, esp. with regard to its methods, validity, and scope. Epistemology is the investigation of what distinguishes justified belief from opinion.!

    132. Epistemology (4)! Central problems in epistemology such as skepticism; a priori knowledge; knowledge of other minds; self-knowledge; the problem of induction; foundationalist, coherence, and causal theories of knowledge. Prerequisites: upper-division standing or consent of instructor.!

    Philosophy!

  • A good scientist, like a good detective, uses his or her judgment. Not all possibilities are worth considering, not because they are impossible, or because the evidence at hand rules them out, but because, given what we know about how the world works in general, they seem irrelevant and far-fetched. It's not reasonable to worry about far-fetched possibilities!

    Is Science Value-Free?! by ALVA NOË!

    Reasonableness, explanatory adequacy, predictive power, simplicity, coherence: these are the stuff of science!

    Theories and hypotheses are supported based on data, or falsified likewise. But it is a mistake, sometimes perpetuated by those in science themselves, to say we have "proven" anything to be "true." To avoid those entanglements, we speak in probabilities, giving more of our concerns to those things with higher probabilities than lower probabilities. ! --Matthew Bonnan!

  • What is a parasitic agent? How do they replicate? How do they spread?

  • Which factors affect the nature of an obligate parasite?

    Host population density Network of host interactions: local vs. distant Type of interactions (proximity, direct casual contact, intimate contact) Biological or cultural behaviors of the host (frequency of intimate contact, concurrent sex, ritual burial of the dead, sanitation) Presence of a vector Host metabolism Environmental temperature dynamics (seasonal fluctuations) Host mechanisms of immunity

  • SIVcpz is only mildly pathogenic in chimps (close to HIV-1) SIVsm is probably mildly pathogenic sooty mangabey (close

    to HIV-2) each is said to have “natural immunity” Either causes AIDs in other apes (like ourselves) or monkeys We will see later that HIV jumped to humans >5 times from

    ~1920’s 1960’s: end of colonialism…people in Africa move to cities

    and become more mobile 1969: American teenager in St. Louis-HIV infected

    (discovered later) 1976: July 4th, Tall ships sail into NYC, sailors from all over

    the world 1976: Dr. Grethe Rask falls seriously ill in Kinshasa, Zaire

    after 2 yrs of weariness, dies in 1977 of unnamed disease 1980: HIV has landed in a highly connected network of the

    gay flight attendants and iv drug users (And the Band Played On, Randy Shilts)

    1981: Five homosexual men present themselves at Los Angeles hospitals

    Forever more: HIV causes a world-wide epidemic

  • Six degrees of separation: how does community structure affect disease transmission?

  • Scale-free, small-worlds network [Barabási & Albert]

  • Virulence and the course of disease correlates with mechanisms of transmission!

    Pathogens transmitted by respiratory droplets require host mobility (e.g. rhinovirus)!

    Parasites that utilize an intermediate vector for transmission can immobilize the host and be much more virulent (malaria, yellow fever, dengue, etc)!

    Pathogens in diffuse populations, e.g., Herpes viruses in all animals—always chronic, never cleared!

    Secondary (reservoir) hosts (influenza, ebola, etc)!

    Parasites that are enduring and depend upon the mobility of a healthy host can be much more virulent (anthrax, small pox)!

    Venereal transmission-always chronic diseases caused by persistent infectious agents (syphilis, HSV2, HIV)!

    Plague time, Paul W. Ewald

  • Which factors affect the nature of an obligate parasite?

    Host population density Network of host interactions: local vs. distant Type of interactions (proximity, direct casual contact, intimate contact) Biological or cultural behaviors of the host (frequency of intimate contact, concurrent sex, ritual burial of the dead, sanitation) Presence of a vector Host metabolism Environmental temperature dynamics (seasonal fluctuations) Host mechanisms of immunity

  • Disease Transmission Incubation Contagious period [time-course of infection] Etiologic Agent

    Common Cold respiratory spread 2-5 d 40 d (Ordinary) variola major

    Bubonic Plague rsprtry/vector spread 2-5 d 4 d ... Yersinia pestis

    Whooping cough respiratory spread 7-10 d > 21 d Bordetella pertussis

    Diphtheria respiratory spread 2-7 d 14 d Lysogenized C. diphtheriae

    Chicken Pox respiratory spread 10-21 d 6-8 d varicella (a-herpesvirus)

    Influenza respiratory spread 1-3 d 5-7 d influenza A

    Cholera water 1-5 d variable Lysogenized V. cholerae

    Our favorite modern diseases (neolithic era)

  • Disease Transmission Incubation Contagious period [time-course of infection] Etiologic Agent

    Common Cold respiratory spread 2-5 d 40 d (Ordinary) variola major

    Bubonic Plague vector spread 2-5 d 4 d ... Yersinia pestis

    Whooping cough respiratory spread 7-10 d > 21 d Bordetella pertussis

    Diphtheria respiratory spread 2-7 d 14 d Lysogenized C. diphtheriae

    Chicken Pox respiratory spread 10-21 d 6-8 d varicella (a-herpesvirus)

    Influenza respiratory spread 1-3 d 5-7 d influenza A

    Cholera water 1-5 d variable Lysogenized V. cholerae

    10,000 years ago - Late paleolithic

  • Islands of high density populations! Permanent residence! Close contact with domesticated herd animals! Non-existent public health measures! Increased birth rate!

    Holocene human ecology! (10,000 BCE to present) The agricultural revolution!

    Late Pleistocene human ecology! (60,000-10,000 BCE)! Hunter-gatherers! sparse populations! widely dispersed! constantly on the move!

  • Disease Transmission Time-course of infection Etiologic Agent

    Head and body lice contact permanent Pediculus humanus

    Protozoans various long-permanent Giardia, Entamoeba, Cyclospora, Cryptosporidium, etc

    Helminths, eg pinworms contact, oral-fecal weeks to permanent Nematodes, cestodes, trematodes

    None in healthy hosts contact permanent Cytomegalovirus (HHV-5) [b-herpesvirus]

    mononucleosis Burket’s Lymphoma contact permanent

    Epstein-Barr Virus [g-herpesvirus]

    Mouth and genital herpes contact permanent

    HSV Type I and Type II [a-herpesvirus]

    Hepatitis B contact or vertical Newborns, permanent Hepatitis B virus

    Syphilis, Yaws, Pinta contact long-permanent Treponemal spirochetes

    TB respiratory spread permanent (2%) M. tuberculosis

    Paleolithic diseases

  • Which factors affect the nature of an obligate parasite?

    Host population density Network of host interactions: local vs. distant Type of interactions (pro