1. Unit 3: Biology, Transmission, Natural History, Prevention and Treatment of HIV Infection and AIDS
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2. 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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3. 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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4. 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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5. 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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6. 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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7. Table 3.1. HIV-1 versus HIV-2 HIV-1 HIV-2 Geographic Distribution
HIV-1
HIV-2
Geographic Distribution
Worldwide
Primarily confined to West Africa, although cases have been reported in Europe, Asia, and Latin America
Subtypes
Major group, M, is classified into 10 subtypes; additional divergent strains are known as group O
Five genetic subtypes
Natural History
More easily transmitted than HIV-2, and faster progression to AIDS
Less easily transmitted than HIV-1, and slower progression to AIDS
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8. How HIV is Transmitted in Sub-Saharan 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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9. Figure 3.1. Methods of HIV Transmission in Sub-Saharan Africa
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10. 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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11. 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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12. 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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13. 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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14. 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)
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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15. 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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16. 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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17. 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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18. 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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19. 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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20. 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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21. 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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22. Answers to Warm Up Questions, Cont.
2. How many major strains of HIV exist?
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23. Answers to Warm Up Questions, Cont.
2. How many major strains of HIV exist? Two
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24. 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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25. 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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26. 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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27. 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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28. Answers to Warm Up Questions, Cont.
5. True or false? HIV infection and the onset of AIDS occur simultaneously.
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29. Answers to Warm Up Questions, Cont.
5. True or false? HIV infection and the onset of AIDS occur simultaneously. False
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30. 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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31. 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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32. 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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33. 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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34. 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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35. 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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36. Answers to Warm Up Questions, Cont.
9. List the three main types of antiretroviral drugs used to treat HIV infection.
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37. 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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38. 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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39. 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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40. 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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41. 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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42. 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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43. 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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44. 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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45. 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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46. Answers to Warm Up Questions, Cont.
14. ____________ is the term used to describe the treatment to prevent or suppress infection.
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47. 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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48. 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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49. Small Group Reports
Select one member from your group to present your answers.
Discuss with the rest of the class.
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50. Case Study: Instructions
Try this case study individually.
We’ll discuss the answers in class.
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51. 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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52. 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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