1. Human Biology Sylvia S. Mader Michael Windelspecht
Infectious Diseases Supplement
Lecture Outline
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2. Infectious Diseases Epidemiology: the study of diseases in populations
S.1 AIDS and Other Pandemics
Infectious Diseases
Epidemiology: the study of diseases in populations
Infectious Diseases: diseases caused by pathogens
Bacteria
Viruses
Fungi
Parasites
Protozoans
Prions

3. S.1 AIDS and Other Pandemics
Infectious Diseases
Epidemic: more cases of the disease than expected in a certain area for a certain period
Outbreak: if the epidemic is confined to a
local area
Pandemic: a global epidemic

4. History of HIV Originated in Africa in the late 1950’s
S.1 AIDS and Other Pandemics
History of HIV
Originated in Africa in the late 1950’s
Originally found in nonhuman primates and may have mutated
First documented in the US in 1969
HIV was found to be the cause of AIDS in

5. Prevalence of HIV ~ 33.2 million people are living with HIV
S.1 AIDS and Other Pandemics
Prevalence of HIV
~ 33.2 million people are living with HIV
At least 0.8% of adults have HIV
2.1 million people died during 2007
Over 25 million people have died since the beginning of the epidemic
Most people living with HIV live in developing countries

6. Prevalence of HIV S.1 AIDS and Other Pandemics Eastern Europe
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Eastern Europe
and Central Asia
1.6million
(1.2-–2.1million
Eastern Europe
and Central Asia
1.6million
(1.2-–2.1million
Western and
Central Europe
760,000
(600,000-–1.1million
Western and
Central Europe
760,000
(600,000-–1.1million
North America
1.3million
(480,000-–1.9million
North America
1.3million
(480,000-–1.9million
East Asia
800,000
(620,000-–960,000
East Asia
800,000
(620,000-–960,000
Caribbean
230,000
(210,000-–270,000
Caribbean
230,000
(210,000-–270,000
Middle East
and North Africa
380,000
(270,000-–500,000
Middle East
and North Africa
380,000
(270,000-–500,000
South and
Southeast Asia
4.0 million
( million)
South and
Southeast Asia
4.0 million
( million)
Latin America
1.6million
(1.4–1.9million)
Latin America
1.6million
(1.4–1.9million)
Sub-Saharan
Africa
22.5million
(20.9–24.3million)
Sub-Saharan
Africa
22.5million
(20.9–24.3million)
Oceania
75,000
(53,000-–120,000)
Oceania
75,000
(53,000-–120,000)

7. S.1 AIDS and Other Pandemics
Prevalence of HIV

8. Phases of HIV infection
S.1 AIDS and Other Pandemics
Phases of HIV infection
Category A:
Asymptomatic but highly infectious
CD4 count above 500 cells/mm3
Category B:
Has one or more of a variety of symptoms related to an impaired immune system
CD4 count between cells/mm3
Category C:
At this point the person has AIDS in which they have one or more of the AIDS opportunistic infections that eventually is the cause of death
CD4 count has fallen below 200 cells/mm3

9. Phases of HIV infection
S.1 AIDS and Other Pandemics
Phases of HIV infection
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107
Category A: Acute Phase
Category B: Chronic Phase
Category C: A IDS
1,100
1,000
106
900
800
105
700
CD4 T lymphocytes
CD 4T Lymphocyte in Blood (permm3)
600
HIV in Plasma (per mL)
500
104
400
300
103
200
HIV
100
102 1 2 3 4 5 6 7 8 9 10
Years Since Infection

10. Structure of HIV Two single strands of RNA
S.1 AIDS and Other Pandemics
Structure of HIV
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RNA
envelope
Two single strands of RNA
Enveloped with spikes (Gp120)
Carries 3 enzymes
Reverse transcriptase
Integrase
Protease
protease
gp120
(spike)
integrase
capsid
matrix
reverse
transcriptase

11. HIV life cycle/replication
S.1 AIDS and Other Pandemics
HIV life cycle/replication
Attachment: Gp120 binds to CD4 receptors
Fusion: HIV fuses with the cell membrane
Entry: uncoating occurs to release the RNA
Reverse transcriptase: RNA is transcribed into double-stranded DNA
Integration: new DNA becomes part of the host cell’s DNA in the nucleus (provirus)
Biosynthesis: produces more viral RNA and proteins
Assembly: assemble new parts into viral particles
Budding: viral particles bud from the cell membrane taking a piece with it that becomes the envelope
Transmission to a new host: passed to a new host

12. HIV life cycle S.1 AIDS and Other Pandemics plasma membrane 2. Fusion
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plasma membrane
2. Fusion
envelope
spike
capsid
8. Budding
1. Attachment
protease
capsid
3. Entry
viral RNA
ribosome
reverse
transcriptase
viral
RNA
c DNA
6. Biosynthesis
and cleavage
7. Assembly
4. Reverse
transcription
receptor
viral
RNA
host DNA
double-stranded DNA
HIV
provirus
integrase
5. Integration
nuclear pore
Nucleus
Cytoplasm

13. Transmission and prevention of HIV
S.1 AIDS and Other Pandemics
Transmission and prevention of HIV
Transmission is through sexual contact, dirty needles, a blood transfusion, or to a baby from their mother
Globally, heterosexual sex is the most common mode of transmission
HIV is not passed through casual contact
Prevention is through abstinence, sex with only one uninfected partner, and proper, consistent use of condoms

14. HIV testing and treatment
S.1 AIDS and Other Pandemics
HIV testing and treatment
HIV tests test for the presence of antibodies not the virus itself
Most people develop antibodies within 2-8 weeks of infection but it can take 3-6 months (consider this when being tested!)
Treatments:
Drug therapy: highly active antiretroviral therapy (HAART) uses a combination of drugs to inhibit HIV replication
Vaccines: scientists have studied 50 different preventive vaccines and 30 therapeutic vaccines

15. Science Focus: HIV vaccines
S.1 AIDS and Other Pandemics
Science Focus: HIV vaccines
Difficulties in producing a vaccine development:
HIV viruses locally and globally are genetically different
No vaccine so far is 100% effective and may only provide short-term protection
Concerns that the vaccine may increase the chances of getting the disease or even cause the disease
There is no ideal animal model for testing besides humans themselves

16. Tuberculosis 1/3 of the world’s population has been exposed to TB
S.1 AIDS and Other Pandemics
Tuberculosis
1/3 of the world’s population has been exposed to TB
~ 9 million people are infected and 2 million die each year
Cause and Transmission:
Mycobacterium tuberculosis
Spread when an infected person coughs, sings, or sneezes
Likelihood of infection increase with length and frequency of exposure
Disease:
Incubation period is from 4 to 12 weeks
Latent TB
Active TB
Treatment and Prevention:
Multiple anti-TB drugs are given simultaneously for 12 to 24 months
Common drugs: INH, RIF, ethambutol, and pyrazinamide
It takes at least 6 months to kill all of the TB in the body
Active TB patients are isolated and anyone exposed is treated

17. Malaria ~ 350-500 million cases and over 1 million deaths each year
S.1 AIDS and Other Pandemics
Malaria
~ million cases and over 1 million deaths each year
Cause and Transmission:
Four species of Plasmodium infect humans
Spread by the female Anopheles gambiae mosquito
Disease:
Incubation period is from 7 to 30 days
Symptoms range from very mild to fatal
People develop a flulike illness with chills and fever
Treatment and Prevention:
Antimalarial drugs include quinine and artesunate
Prevention includes eliminating the mosquito by removing its breeding sites

18. S.2 Emerging Diseases
Emerging Diseases
National Institute of Allergy and Infectious Diseases (NIAID) lists 18 pathogens that are newly recognized in the last two decades.
avian influenza (H5N1)
swine flu (H1N1)
severe acute respiratory syndrome (SARS)
Reemerging Diseases: diseases that have reappeared after a significant decline in incidence
Streptococcus: bacteria that causes strep throat and other infections

19. How does antibiotic resistance develop?
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not drug resistant
drug-resistant mutant
exposure
to drug
Remaining
population
grows
overtime.
early
late
a. Initial population of microbes
b. Weaker (non resistant) cells killed
by antibiotic; resistant cells survive.
c. Most cells are now resistant.