Download chaptsup_lecture Supp Mader Disease

Human Biology
Sylvia S. Mader
Michael Windelspecht
Infectious
Diseases
Supplement
Lecture Outline
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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
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
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 19831984
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
S.1 AIDS and Other Pandemics
Prevalence of HIV
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North America
1.3million
(480,000-–1.9million
Caribbean
230,000
(210,000-–270,000
Latin America
1.6million
(1.4–1.9million)
Western and
Central Europe
760,000
(600,000-–1.1million
Middle East
and North Africa
380,000
(270,000-–500,000
Sub-Saharan
Africa
22.5million
(20.9–24.3million)
Eastern Europe
and Central Asia
1.6million
(1.2-–2.1million
East Asia
800,000
(620,000-–960,000
South and
Southeast Asia
4.0 million
(3.3-5.1 million)
Oceania
75,000
(53,000-–120,000)
S.1 AIDS and Other Pandemics
Prevalence of HIV
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 200-499 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
S.1 AIDS and Other Pandemics
Phases of HIV infection
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Category B: Chronic Phase
Category C: A IDS
107
1,100
1,000
106
900
800
105
CD4 T lymphocytes
700
600
500
104
400
300
200
103
HIV
100
102
0
1
2
3
4
5
6
Years Since Infection
7
8
9
10
HIV in Plasma (per mL)
CD 4T Lymphocyte in Blood (permm3)
Category A: Acute Phase
S.1 AIDS and Other Pandemics
Structure of HIV
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RNA
envelope
protease
gp120
(spike)
• Two single strands
of RNA
• Enveloped with
spikes (Gp120)
• Carries 3 enzymes
– Reverse
transcriptase
– Integrase
– Protease
integrase
capsid
reverse
transcriptase
matrix
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
S.1 AIDS and Other Pandemics
HIV life cycle
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plasma membrane
2. Fusion
envelope
spike
capsid
8. Budding
protease
1. Attachment
3. Entry
viral
RNA
receptor
viral RNA
ribosome
capsid
reverse
transcriptase
c DNA
6. Biosynthesis
and cleavage
7. Assembly
4. Reverse
transcription
viral
RNA
host DNA
HIV
provirus
double-stranded DNA
integrase
5. Integration
nuclear pore
Nucleus
Cytoplasm
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
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
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
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
S.1 AIDS and Other Pandemics
Malaria
• ~ 350-500 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
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
S.3 Antibiotic Resistance
How does antibiotic resistance
develop?
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not drug resistant
drug-resistant mutant
exposure
to drug
a. Initial population of microbes
Remaining
population
grows
overtime.
b. Weaker (non resistant) cells killed
by antibiotic; resistant cells survive.
c. Most cells are now resistant.