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.
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BICD 136hedrick.ucsd.edu/BICD136/Lectures/Lecture1-Intro.pdf · 2014. 9. 17. · A good scientist, like a good detective, uses his or her judgment. Not all possibilities are worth
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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?
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 <7 d 200+ viruses: rhino; corona; other
Measles (Rubeola)
respiratory spread 9-12 d ~4-9 d Genus: Morbillivirus
Mumps respiratory spread 16-18 d 15 d mumps virus (paramyxovirus)
Rubella respiratory spread 14-21 d 17 d rubella virus (togovirus)
Small Pox respiratory spread 12 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 <7 d 200+ viruses: rhino; corona; other
Measles (Rubeola)
respiratory spread 9-12 d ~4-9 d Genus: Morbillivirus
Mumps respiratory spread 16-18 d 15 d mumps virus (paramyxovirus)
Rubella respiratory spread 14-21 d 17 d rubella virus (togovirus)
Small Pox respiratory spread 12 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
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 (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
What is Epidemiology?!• Epi means “on or upon.”!• Demos means “people, population.”!• Epidemiology is the study of how diseases affect whole
communities.!• Infectious disease is about HOST-PATHOGEN interactions!• All living entities are parasitized!• The nature of the parasite is evolved to fit the host, its
ecology, its co-evolved mechanisms of immunity!
Epidemiology Definitions!• Endemic—diseases that persist at
a moderate or steady state level within a given geographic area.!• Epidemic—an unusually high
number of cases in excess of normal expectation of a similar illness in a population, community or region.!• Sporadic—disease outbreaks that
have no pattern of occurrence in a given time or location.!
Adapted from Gordis, Leon. Epidemiology. Second Edition W.B. Saunders, 2000.!
• Pandemic—a worldwide epidemic.!• Morbidity—refers to illness or disease state.!• Mortality—numbers of deaths correlated with a particular
disease.!• Incidence—measurement of morbidity; the number of new
cases of a disease that occurs in a specified period of time in a susceptible population.!
• Prevalence—measurement of morbidity; number of cases in an existing population at a specified time.!
• Carrier—an individual who harbors the virus but is not infected as measured by serologic methods or by evidence of clinical illness.!
Epidemiology Definitions, cont’d!
• Mode of transmission—how an infectious disease is spread from host to host!
• Etiological agent/pathogen—disease-causing agent.!• Reservoir—where the etiological agent lives, grows, and
multiplies (probably endemic to a particular host).!• Vector—an animal that spreads an agent from host to host
(e.g., mosquitoes that spread malaria or yellow fever)!• Communicable period—time period when an infected individual
or animal is contagious and he/she can directly or indirectly infect another person, animal, or arthropod.!
• Convalescence—the recovery period after an illness.!• Zoonosis—any infection or infectious disease transmissible
from animals to humans.!
Prevention and Containment of Infectious Diseases: Quarantine!
• Practice of quarantine is still used today to prevent person-to-person transmission of infectious diseases (e.g., SARS outbreak, tuberculosis).!
Some diseases are acute. They strike and they resolve relatively quickly!Some diseases are persistent, they are never cleared and cause life-long infection!Some diseases are mild!Some diseases are often lethal!Is there a conceptual basis for these differences?!
Acute, crowd epidemic diseases 10000 BCE - 1491 CE
None
Common Cold
Measles (Rubeola)
Mumps
Rubella
Small Pox
Bubonic Plague
Whooping cough
Chicken Pox
Polio
Scalett Fever
Diphtheria
Typhoid
Hepatitis A
Meningitis
Influenza
Cholera
Disease-causing agents evolve to accommodate the ecology of their hosts: density, mode and frequency of contact…not the specifics of immune mechanisms!!These principles determine the persistence and virulence of the infectious agent !
Smallpox (430 BC? - 1979): Killed more than 300 million people worldwide in the 20th century alone, and a large proportion of the native inhabitants of the Americas Smallpox is the only human infectious disease to have been completely eradicated from nature. It is also the most stable virus known!
Spanish Flu (1918 - 1919): Killed ~50 million people worldwide in less than 2 years Occurred during and at the end of WWI (Barracks, trenches, high density aggregation of people). People sometimes died within hours of noticing symptoms
Black Death (1340 - 1771): Killed 75 million people worldwide and in 4 years (1347-1351), 1/3 of the population of Europe. Greatly changed culture
Malaria (1600 - today): Kills about 2 million people per year, affects about 500 million people per year
AIDS (1981 - today): Killed ~40 million people worldwide, thus far--the topic of this course; since the beginning of the pandemic, nearly 78 million people have contracted HIV and close to 39 million have died of AIDS-related causes.
Top 5 killer epidemics; Caused by? Transmitted by?
Acute - Chronic Infections!Acute Infection!• Acute infections show
symptoms very rapidly after infection occurs and once the immune response curtails the agent, the symptoms recede. Once a person recovers he or she may be resistant to recurrent infections by the same agent.!
Chronic Infection!• The infected person
responds to the agent immunologically but does not clear the virus entirely.!
• Chronic infections require fewer susceptibles than acute infections and so can be maintained in smaller populations. !
• HIV/AIDS is a chronic infection.!
Crowd-epidemic diseases! Long co-evolved diseases!
Long co-evolved chronic diseases Crowd-epidemic diseases
Disease Vaccine? Disease Vaccine?
Head and body lice NO Common Cold NO
Protozoans NO Measles (Rubeola) YES
Helminths, eg pinworms NO Mumps YES
CMV NO Rubella YES
mononucleosis, Burket’s NO Small Pox YES
TB NO Bubonic Plague Not yet
Yaws, syphillus NO Whooping cough YES
Oral and genital herpes NO Diphtheria YES
HIV NO Chicken Pox YES
Hepatitis B YES Influenza YES
HPV YES Cholera YES
Vaccines
Trade-off theory!• Extent and speed of pathogen replication
equates with virulence!• Transmission depends upon replication
and the ability of the host to exist long-enough to spread the infection!
• Virulence is almost always self-limiting and balanced against transmission!
Figure 02.F01: Population factors that affect epidemics.!
Experimental population variation in the face of disease!
Ectromelia (mouse pox)!
Pasteurella muris!No disease!
Observed with
disease!
A=6! A=0.3!
What are factors that control virulence in:!SARS-coronavirus!West Nile Virus-flavivirus!Hantavirus-bunyavirus, haemorrahgic fever!What about HIV, how can it be so virulent and spread so far across the earth?!