1. Module 1: Overview of HIV Infection
2005
Module 1: Overview of HIV Infection
Module 1: Overview of HIV Infection

2. Learning Objectives At the end of this module, you will be able to:
Describe the difference between HIV infection and AIDS
Discuss the HIV epidemics globally, regionally, and locally in terms of number of people affected
Define the terms: antibody and antigen
Explain how “window period” may affect HIV testing results
Describe the progression of HIV infection

3. Content Overview What is HIV? What is AIDS? The HIV pandemic
HIV transmission
Window period
Stages of HIV infection

4. Human: Infecting human beings
2005
What is HIV?
Human: Infecting human beings
Immunodeficiency: Decrease or weakness in the body’s ability to fight off infections and illnesses
Virus: A pathogen having the ability to replicate only inside a living cell
HIV stands for Human Immunodeficiency Virus. It is the virus that causes AIDS.
Module 1: Overview of HIV Infection

5. Types of HIV Virus HIV 1 HIV 2
2005
Types of HIV Virus
HIV 1
Most common in sub-Saharan Africa and throughout the world
Groups M, N, and O
Pandemic dominated by Group M
Group M comprised of subtypes A - J
HIV 2
Most often found in West Central Africa, parts of Europe and India
Both produce the same patterns of illness. HIV2 causes a more slow progress of disease than those with HIV 1
It is important for tests to detect the HIV subtypes that are circulating in the region. Otherwise, testing may lead to false negative results.
Module 1: Overview of HIV Infection

6. Structure of HIV Envelope Core p24 Reverse Transcriptase RNA
2005
Structure of HIV
Envelope
Reverse Transcriptase
Core p24
RNA
This is the structure of the HIV virus. It looks like a spherical particle of 80 to 100 mm in diameter. Like all viruses, it is made up of 2 main elements: the external envelope, and the internal core.
HIV is a retrovirus
Viruses in general are made up of a core with RNA or DNA and sometimes an external envelope
Module 1: Overview of HIV Infection

7. Acquired: To come into possession of something new
2005
What is AIDS?
Acquired: To come into possession of something new
Immune Deficiency: Decrease or weakness in the body’s ability to fight off infections and illnesses
Syndrome: A group of signs and symptoms that occur together and characterize a particular abnormality
HIV infection leads to a weakened immune system. This makes a person with HIV vulnerable to a group of illness, e.g., opportunistic infections, that would not as easily affect a healthy person
AIDS results when HIV infection progresses to an advanced stage, damaging the immune system to a point at which the body can no longer fight illness.
AIDS is a syndrome because it is characterized by a group of illnesses
Drugs are available which can treat HIV and AIDS.
These drugs are called antiretrovirals (ARVs). They prevent the virus from replicating and slow the progress of the disease, but there is still no cure for AIDS or vaccine to prevent HIV transmission.
AIDS is the final stage of the disease caused by infection with a type of virus called HIV.
Module 1: Overview of HIV Infection

8. HIV vs. AIDS HIV is the virus that causes AIDS
Not everyone who is infected with HIV has AIDS
Everyone with AIDS is infected with HIV
AIDS is result of the progression of HIV Infection
Anyone infected with HIV, although healthy, can still transmit the virus to another person

9. 2005
How is HIV Transmitted?
Unprotected sexual contact with an infected partner
Exposure of broken skin or wound to infected blood or body fluids
Transfusion with HIV-infected blood
Injection with contaminated objects
Mother to child during pregnancy, birth or breastfeeding
Module 1: Overview of HIV Infection

10. North Africa & Middle East
2005
HIV: A Global Pandemic
Eastern Europe & Central Asia
1.2 – 1.8 million
Western Europe –
North America
– 1.2 million
East Asia & Pacific
– 1.3 million
North Africa & Middle East –
South
& South-East Asia
4.6 – 8.2 million
Caribbean –
Sub-Saharan Africa
25.0 – 28.2 million
Latin America
1.3 – 1.9 million
Australia
& New Zealand –
This slide produced by UNAIDS is familiar to many of you and provides estimates for the numbers of persons living with HIV in different continents. A total of between 34 and 46 million persons live with HIV; most of these in Africa.
HIV infection is a worldwide epidemic – a pandemic – affecting people everywhere.
Adults and children estimated to be living with HIV/AIDS (2003): 34 – 46 million total
Module 1: Overview of HIV Infection

11. HIV Epidemic in Sub-Saharan Africa

12. HIV Epidemic: Local Facts & Impact
Insert -
Local HIV/AIDS Facts
Local Impact

13. Basic Terms
Antigen: A substance which is recognized as foreign by the immune system. Antigens can be part of an organism or virus, e.g., envelope, core (p24) and triggers antibody production.
Antibody: A protein (immunoglobulin) made by the body’s immune system to recognize and attack foreign substances

14. Testing for Viral Infection and Immune Response
2005
Testing for Viral Infection and Immune Response
Viral infection
Viral Load
p24 Antigen
Immune response
Antibody (IgG, IgM)
Cellular response (CD4)
Over a period of time, HIV infects and kills white blood cells called CD4 lymphocytes or (T cells), leaving the body unable to fight off certain kinds of infections
Both T & B cells are types of white blood cells called lymphocytes
Helper T-Cells (also called T4 or CD4+ cells) help other cells destroy infective organisms.  Suppressor T-Cells (also called T8 or CD8+ cells) suppress the activity of other lymphocytes so they don't destroy normal tissue.  Killer T-Cells (also called cytotoxic T lymphocytes, or CTLs, and are another kind of T8 or CD8+ cell) recognize and destroy abnormal or infected cells.
Module 1: Overview of HIV Infection

15. Evolution of Antibodies
Window Period

16. 2005
Window Period
Time from initial infection with HIV until antibodies are detected by a single test
Usually 3-8 weeks before antibodies are detected
May test false-negative for HIV antibodies during this time period
Can still pass the virus to others during this period
Represents the stage when you have been infected with HIV, but your body hasn’t created antibodies.
“Seroconversion” is a term used to describe the change when antibodies are produced and the blood is tested positive.
Seroconversion occurs when your body first begins to produce antibodies to HIV. In other words, your blood may be negative to HIV antibodies during a time period after infection, but may convert to positive to HIV antibodies after a certain period. Generally 3-8 weeks after the initial infection.
Module 1: Overview of HIV Infection

17. 2005
Disease Progression
Severity of illness is determined by amount of virus in the body (increasing viral load) and the degree of immune suppression (decreasing CD4+ counts)
As the CD4 count declines, the immune function decreases.
Define viral load as the amount of HIV virus circulating in the bloodstream.
Immune suppression, measured by CD4+ cells and total lymphocyte counts, alerts us to the risk of opportunistic infections and the need for prophylactic treatment to prevent such infections from developing.
Module 1: Overview of HIV Infection

18. WHO HIV/AIDS Classification System
2005
WHO HIV/AIDS Classification System
Stage I
Asymptomatic
Stage II
Minor Symptoms
Stage III
Moderate Symptoms
Stage IV
AIDS
HIV infection has various stages from primary infection (or acute phase) to asymptomatic phase (or chronic phase) and late stage disease (or AIDS)
The first weeks after primary infection, seroconversion occurs and is associated with a rapid increase in circulating viral titers and a significant drop in the number of CD4+ cells.
Module 1: Overview of HIV Infection

19. Can Disease Progression Be Delayed?
Prevention and early treatment of opportunistic infections (OIs)
Antiretroviral therapy
Positive living
YES

20. Summary What is HIV? What is AIDS? How does HIV relate to AIDS?
What are the means by which HIV is transmitted?
What is “window period?” How does it affect HIV test results?
What is an antibody? Antigen?
How does HIV infection progress?
How can the disease progression of HIV/AIDS be delayed?