# Presentation: 216406

## Module 1:  Overview of HIV Infection

## 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

## Content Overview

- What is HIV?
- What is AIDS?
- The HIV pandemic
- HIV transmission
- Window period
- Stages of HIV infection

## What is HIV?

- _H_uman:  Infecting human beings
- _I_mmunodeficiency:  Decrease or weakness in the body’s ability to fight off infections and illnesses
- _V_irus:  A pathogen having the ability to replicate only inside a living cell

**Notes:**
HIV stands for Human Immunodeficiency Virus.  It is the virus that causes AIDS.

## 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

**Notes:**
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.

## Structure of HIV

**Envelope**

**Core p24**

**RNA**

**Reverse Transcriptase**

**Notes:**
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

## What is AIDS?

- _A_cquired: To come into possession of something new
- _I_mmune _D_eficiency:  Decrease or weakness in the body’s ability to fight off infections and illnesses
- _S_yndrome:  A group of signs and symptoms that occur together and characterize a particular abnormality

- AIDS is the final stage of the disease caused by infection with a type of virus called HIV.

**Notes:**
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.

## 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

## 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

## HIV: A Global Pandemic

**Adults and children estimated to be living with HIV/AIDS (2003)****: 34 – 46 million total**

**Western Europe**
**520 000 – 680 000**

**North Africa & Middle East**
**470 000 – 730 000**

**Sub-Saharan Africa**
**25.0 – 28.2 million**

**Eastern Europe ****& Central Asia**
**1.2 – 1.8 million**

**South **
**& South-East Asia**
**4.6 – 8.2 million**

**Australia **
**& New Zealand**
**12 000 – 18 000****     **

**North America**
**790 000 – 1.2 million**

**Caribbean**
**350 000 – 590 000**

**Latin America**
**1.3 – 1.9 million**

**East Asia & Pacific**
**700 000 – 1.3 million**

**HIV: A Global Pandemic**

**Notes:**
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.

## HIV Epidemic in Sub-Saharan Africa 

## HIV Epidemic: Local Facts & Impact

*Insert - *
*Local HIV/AIDS Facts *
*Local Impact*

## 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

## Testing for Viral Infection and Immune Response 

**Viral infection**
**Viral Load**
**p24  Antigen**
**Immune response**
**Antibody (IgG, IgM)**
**Cellular response (CD4)**

**Notes:**
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.

## Evolution of Antibodies

**Evolution of Antibodies**

**Window Period**

## 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

**Notes:**
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.

## 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.

**Notes:**
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.

## WHO HIV/AIDS Classification System

**Stage I**
**Asymptomatic**

**Stage II**
**Minor Symptoms**

**Stage III**
**Moderate Symptoms**

**Stage IV**
**AIDS **

**Notes:**
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. 

## Can Disease Progression Be Delayed?

- Prevention and early treatment of opportunistic infections (OIs)
- Antiretroviral therapy
- Positive living

## 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?