Unit 3: Biology, Transmission,
Natural History, Prevention and
Treatment of HIV Infection and
AIDS
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Warm Up Questions: Instructions

Take five minutes now to try the Unit 3 warm
up questions in your manual.

Please do not compare answers with other
participants.

Your answers will not be collected or graded.

We will review your answers at the end of the
unit.
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What You Will Learn

By the end of this unit you should be able to:

explain the basic biology of HIV

describe HIV transmission routes

understand the importance of concurrent STIs in
increasing risk of HIV transmission

discuss the natural history of HIV and list the
major opportunistic infections that occur among
AIDS patients in sub-Saharan Africa
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What You Will Learn, Cont.

By the end of this unit you should be able to:

describe the major elements of HIV prevention
and control programmes

recognise that HIV is treated with antiretroviral
drugs and that treatment involves prevention and
treatment of opportunistic infections
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The Virus

HIV is a retrovirus that causes AIDS.

HIV attacks white blood cells (CD4+
lymphocytes and macrophages).

This weakens the immune system, which
becomes unable to protect against
opportunistic infections and certain types of
cancers.
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HIV Types

Two major types of HIV have been recognised:
HIV-1 and HIV-2

The epidemiology of HIV subtype distribution
and evolution worldwide are critical for several
reasons:

For vaccine development

To trace transmission among individuals and
track the spread of the virus through
countries
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Table 3.1. HIV-1 versus HIV-2
HIV-1
Geographic
Distribution
Worldwide
Subtypes
Major group, M, is
classified into 10 subtypes;
additional divergent strains
are known as group O
Natural
History
More easily transmitted
than HIV-2, and faster
progression to AIDS
HIV-2
Primarily confined to
West Africa, although
cases have been
reported in Europe, Asia,
and Latin America
Five genetic subtypes
Less easily transmitted
than HIV-1, and slower
progression to AIDS
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How HIV is Transmitted in SubSaharan Africa

Sexual Transmission (85%)
 unprotected heterosexual intercourse
 homosexual intercourse between men
 there are no documented cases of sexual
transmission between women

Blood and blood products (5%)
 transfusion, clinical use of blood products, transplant
 unsterile surgical and injection equipment
 sharing syringes among drug users
Mother to child (10%)
 during pregnancy
 at delivery
 through breast feeding

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Figure 3.1. Methods of HIV
Transmission in Sub-Saharan
Africa
5%
10%
Sexual
Perinatal
Parenteral
85%
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Increased Risk of Infection

Exposure



number of sexual partners
HIV-infected primary partner
Transmission

viral load of infected person
type of sexual contact (anal intercourse is riskier
than vaginal; vaginal is riskier than oral)
co-existence of untreated STIs

non-use of barrier methods (condoms)


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Role of STIs

STIs may cause inflammation and ulceration, which
increases the risk of acquiring infection by:
 increasing recruitment of uninfected lymphocytes
to the site of the inflammation
 disrupting the genital epithelium and endothelium
 Due to an immature cervix, adolescent women
more easily acquire some STIs such as
chlamydia.

The role of STIs in HIV transmission is illustrated by
the Mwanza and Rakai/Masaka cases
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Natural History of HIV

In sub-Saharan Africa, median of 9 years from
start of HIV infection to full-blown AIDS (without
treatment).

In sub-Saharan Africa, death occurs usually less
than one year after onset of AIDS (without
treatment).

Very few with HIV avoid symptoms and death.

New ARV treatments have greatly extended life
and reduced disease.
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Prevention of Sexual HIV
Transmission

Decreasing the risk of being exposed



delay age of sexual debut
decrease the numbers of sexual partners
If exposed, decreasing the risk for transmission



consistently use male and female condoms
undergo voluntary testing and counselling, know
your HIV status
treat STIs
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Table 3.2. Avoiding
Blood-Borne Transmission of HIV
Method of
transmission
How to prevent
transfusion
• sterilising or not re-using needles
• screening blood and blood products for
HIV prior to administration
re-use of needles and
surgical instruments
without sterilisation
• sterilisation of surgical instruments
(including those used in traditional
practices such as scarification)
• sterilising or not re-using needles
needle stick injuries to
healthcare workers
• universal precautions for healthcare
workers (for example, use of gloves and
eyewear, proper disposal of needles)
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Prevention of
Mother-to-Child HIV Transmission

Short course antiretroviral treatment

Avoidance of breastfeeding


When replacement feeding is acceptable, feasible,
affordable, sustainable and safe, avoidance of all
breastfeeding by HIV-positive mothers is
recommended.
Significant health risks are associated with using
breast milk substitutes, however, including
malnutrition and exposure to other infections.
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HIV/AIDS Treatment

Antiretroviral drugs are used to treat HIV infection.
 nucleoside reverse transcriptase inhibitors (NRTIs)
 non-nucleoside reverse transcriptase inhibitors
(nNRTIs)
 protease inhibitors (PIs)

Treatment will most likely start when patients develop
clinical symptoms from their immunodeficiency or
reach a CD4+ cell count of less than 350 cells per
mm3.
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HIV/AIDS Treatment, Cont.

HIV treatment also includes diagnosis,
prophylaxis and treatment of selected
opportunistic infections

Anti-TB drugs

Cotrimoxazole prophylaxis can prevent the
onset of some opportunistic infections.

Vaccines for some potential opportunistic
infections, such as pneumococcal disease.
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In Summary

HIV is a virus that can be transmitted
sexually, parenterally or perinatally.

Even so, there are precautions to prevent
each type of transmission, including condom
use, needle sterilisation and short course
antiretroviral treatment during pregnancy.

Treatment includes antiretroviral drugs, and
the prevention and treatment of opportunistic
infections.
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Warm Up Review

Take a few minutes now to look back at your
answers to the warm up questions at the
beginning of the unit.

Make any changes you want to.

We will discuss the questions and answers in
a few minutes.
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Answers to Warm Up Questions
1. Which body cells does HIV infect?
a. respiratory cells
b. skin cells
c. red blood cells
d. white blood cells
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Answers to Warm Up Questions
1. Which body cells does HIV infect?
a. respiratory cells
b. skin cells
c. red blood cells
d. white blood cells
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Answers to Warm Up Questions,
Cont.
2. How many major strains of HIV exist?
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Answers to Warm Up Questions,
Cont.
2. How many major strains of HIV exist? Two
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Answers to Warm Up Questions,
Cont.
3. Which of the following is not a method of HIV
transmission?
a. sexual intercourse
b. casual physical contact
c. blood exchange
d. mother to fetus
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Answers to Warm Up Questions,
Cont.
3. Which of the following is not a method of HIV
transmission?
a. sexual intercourse
b. casual physical contact
c. blood exchange
d. mother to fetus
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Answers to Warm Up Questions,
Cont.
4. What type of infectious agent is HIV?
a. bacterium
b. virus
c. prion
d. none of the above
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Answers to Warm Up Questions,
Cont.
4. What type of infectious agent is HIV?
a. bacterium
b. virus
c. prion
d. none of the above
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Answers to Warm Up Questions,
Cont.
5. True or false? HIV infection and the onset of
AIDS occur simultaneously.
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Answers to Warm Up Questions,
Cont.
5. True or false? HIV infection and the onset of
AIDS occur simultaneously. False
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Answers to Warm Up Questions,
Cont.
6. Which region of the world has the greatest
diversity of HIV subtypes, making the
development of one unique treatment or
vaccine difficult?
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Answers to Warm Up Questions,
Cont.
6. Which region of the world has the greatest
diversity of HIV subtypes, making the
development of one unique treatment or
vaccine difficult? Sub-Saharan Africa
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Answers to Warm Up Questions,
Cont.
7. Which of the following is associated with
increased risk of sexual transmission of HIV?
a. failure to use a male or female condom
b. a greater number of sexual partners
c. a high viral load in an infected partner
d. all of the above
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Answers to Warm Up Questions,
Cont.
7. Which of the following is associated with
increased risk of sexual transmission of HIV?
a. failure to use a male or female condom
b. a greater number of sexual partners
c. a high viral load in an infected partner
d. all of the above
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Answers to Warm Up Questions,
Cont.
8. True or false? The presence of existing
sexually transmitted infections increases the
risk of acquiring HIV during sexual
intercourse.
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Answers to Warm Up Questions,
Cont.
8. True or false? The presence of existing
sexually transmitted infections increases the
risk of acquiring HIV during sexual
intercourse. True
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Answers to Warm Up Questions,
Cont.
9. List the three main types of antiretroviral
drugs used to treat HIV infection.
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Answers to Warm Up Questions,
Cont.
9. List the three main types of antiretroviral
drugs used to treat HIV infection.



nucleoside reverse transcriptase
inhibitors (NRTIs)
non-nucleoside reverse transcriptase
inhibitors (nNRTIs)
protease inhibitors (PIs)
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Answers to Warm Up Questions,
Cont.
10. Which of the following ultimately fatal
opportunistic infections commonly occur(s)
in AIDS patients?
a. herpes zoster
b. fungal infections
c. tuberculosis
d. all of the above
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Answers to Warm Up Questions,
Cont.
10. Which of the following ultimately fatal
opportunistic infections commonly occur(s)
in AIDS patients?
a. herpes zoster
b. fungal infections
c. tuberculosis
d. all of the above
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Answers to Warm Up Questions,
Cont.
11. True or false? A vaccine for the prevention
of HIV infection is currently available.
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Answers to Warm Up Questions,
Cont.
11. True or false? A vaccine for the prevention
of HIV infection is currently available. False
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Answers to Warm Up Questions,
Cont.
12. True or false? Some STIs such as
chlamydia are biologically more easily
acquired by young women, making them
more susceptible to HIV infection.
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Answers to Warm Up Questions,
Cont.
12. True or false? Some STIs such as
chlamydia are biologically more easily
acquired by young women, making them
more susceptible to HIV infection. True
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Answers to Warm Up Questions,
Cont.
13. Match the type of transmission with the
percentage of infection that it accounts for
(in sub-Saharan Africa):
___ sexual intercourse
a. 10%
___ perinatal transmission
b. 5%
___ blood exchange
c. 85%
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Answers to Warm Up Questions,
Cont.
13. Match the type of transmission with the
percentage of infection that it accounts for
(in sub-Saharan Africa):
_c_ sexual intercourse
a. 10%
_a_ perinatal transmission
b. 5%
_b_ blood exchange
c. 85%
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Answers to Warm Up Questions,
Cont.
14. ____________ is the term used to describe
the treatment to prevent or suppress
infection.
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Answers to Warm Up Questions,
Cont.
14. Prophylaxis is the term used to describe
the treatment to prevent or suppress
infection.
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Small Group Discussion:
Instructions

Get into small groups to discuss these
questions.

Choose a speaker for your group who will
report back to the class.

Take 15 minutes for this exercise.
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Small Group Reports

Select one member from your group to
present your answers.

Discuss with the rest of the class.
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Case Study: Instructions

Try this case study individually.

We’ll discuss the answers in class.
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Case Study Review

Follow along as we go over the case study in
class.

Discuss your answers with the rest of the
class.
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Questions, Process Check

Do you have any questions on the information
we just covered?

Are you happy with how we worked on Unit 3?

Do you want to try something different that will
help the group?
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