Lesson 1



After completing this lesson, you will be able to:

·        give the full meanings of HIV and AIDS;

·        explain what a virus is;

·        name two types of HIV; and

·        state how HIV is contracted.


 

HIV is the shortened form for Human Immunodeficiency Virus. It is a virus, such as the virus that causes the flu or cold. A virus is a minute particle that lives as a parasite in plants, animals, and bacteria. It consists of an inside (core) made of a substance known as nucleic acid and an outside (sheath) made of protein. Viruses can only replicate within living cells and are not considered to be independent living organisms.

In order to make more viruses (and to do all of the other nasty things that viruses do), a virus has to infect a cell. HIV mostly infects the white blood cells of the body’s immune system. These cells are known as T-cells or CD4 cells.  Once inside the T-cell or CD4 cell, HIV starts producing millions of little viruses, which eventually kill the cell and then go out to infect other cells. All of the drugs marketed to treat HIV work by interfering with this process

 

If one is infected with HIV, the body will try to fight the infection. It will make "antibodies", special molecules that are supposed to fight HIV. When you get a blood test for HIV, the test looks for these antibodies. If a person has them in the blood, it means that the person has HIV infection. People who have the HIV antibodies are called "HIV-Positive".

 

Infection with HIV does not necessarily mean that a person has AIDS. Some people who have HIV infection may not develop any of the clinical illnesses that define the full-blown disease of AIDS for ten years or more. Physicians prefer to use the term AIDS for cases where a person has reached the final, life-threatening stage of HIV infection.

 

What about AIDS? AIDS is a shortened form for Acquired Immune Deficiency Syndrome. It is a condition caused by HIV. This virus, as stated earlier, attacks the immune system, the body's "security force" that fights off infections. When the immune system breaks down, this protection is lost and can lead to the development of many serious, often deadly infections and cancers. These are called "opportunistic infections (OIs)" because they take advantage of the body's weakened defenses. You have heard it said that someone "died of AIDS." This is not entirely accurate, since it is the opportunistic infections that cause death. AIDS is the condition that lets the OIs take hold.

 

There are some specific criteria for determining when a person living with HIV progresses to AIDS. One thing they look at is T-cell counts: if a person falls below 200 T4 cells, then they have officially progressed to AIDS. Another thing they look for are OIs: if an HIV+ individual is diagnosed with an opportunistic infection the list of over two dozen possible HIV-related OIs, then they are diagnosed with AIDS.

 

What is a Virus?

 

A virus is an infectious agent that is found in virtually all life forms, including humans, animals, plants, fungi, and bacteria. Viruses consist of two major parts- an outer protective coat called a capsid which is made of protein; and an inside which consists of genetic material. The genetic material is either of two substances with rather long names. These names have been abbreviated as DNA and RNA. DNA stands for deoxyribonucleic acid while RNA stands for ribonucleic acid. It is also worth noting that the capsid may or may not have an outer envelope made of fat.

Viruses are between 20 and 100 times smaller than bacteria and hence are too small to be seen by the light microscope. Viruses vary in size from the largest poxviruses of about 450 nanometre in length to the smallest polioviruses of about 30 nanometres. (Note: 1 nanometre is a billionth of a metre) Viruses are not considered free-living, since they cannot reproduce outside of a living cell; they have evolved to transmit their genetic information from one cell to another for the purpose of replication.

 

Viruses often damage or kill the cells that they infect, causing disease in infected organisms. A few viruses stimulate cells to grow uncontrollably and produce cancers.

 

Types of HIV

 

There are two types of this virus: HIV-1, which is the primary cause of AIDS worldwide, and HIV-2, found mostly in West Africa. On its surface, HIV carries a protein structure that recognizes and binds only with a specific structure found on the outer surface of certain cells. HIV attacks any cell that has this binding structure. However, white blood cells of the immune system known as T cells, which orchestrate a wide variety of disease-fighting mechanisms, are especially vulnerable to HIV attack. Particularly vulnerable are certain T cells known as CD4 cells. When HIV infects a CD4 cell, it commandeers the genetic tools within the cell to manufacture new HIV virus. The newly formed HIV virus then leaves the cell, destroying the CD4 cell in the process. No existing medical treatment can completely eradicate HIV from the body once it has integrated into human cells.

 

The loss of CD4 cells endangers health because these immune cells help other types of immune cells respond to invading organisms. The average healthy person has over 1,000 CD4 cells per microlitre of blood. In a person infected with HIV, the virus steadily destroys CD4 cells over a period of years, diminishing the cells’ protective ability and weakening the immune system. When the density of CD4 cells drops to 200 cells per microlitre of blood, the infected person becomes vulnerable to any of about 26 opportunistic infections and rare cancers, which take advantage of the weakened immune defences to cause disease.

 

HOW DO YOU GET AIDS?

 

You don't actually "get" AIDS. You might get infected with HIV, and later you might develop AIDS.

 

You can get infected with HIV from anyone who is infected, even if they don't look sick, and even if they haven't tested HIV-positive yet. The blood, vaginal fluid, semen, and breast milk of people infected with HIV has enough of the virus in it to infect other people. Most people get HIV by:

 

 

Getting a transfusion of infected blood used to be a way people got AIDS, but now the blood supply is screened very carefully and the risk is extremely low.

There are no documented cases of HIV being transmitted by tears or saliva, but it is possible to be infected with HIV through oral sex or in rare cases through deep kissing, especially if you have open sores in your mouth or bleeding gums.

 

IS THERE A CURE FOR AIDS?

 

Currently, there is no cure for AIDS. There are drugs that can slow down the HIV virus, and slow down the damage to your immune system. But there is no way to get all the HIV out of your body.

There are other drugs that you can take to prevent or to treat opportunistic infections (OIs). In most cases, these drugs work very well. The newer, stronger anti-HIV drugs have also helped reduce the rates of most OIs. A few OIs, however, are still very difficult to treat.


 

Resources: Three charts: (A) showing the expansion of HIV as Human Immunodeficiency Virus; and AIDS as Acquired Immune Deficiency Syndrome; (B) showing two diagrams- one of the virus – HIV, the other of an AIDS patient; and (C) listing ways of contracting the disease with relevant illustrative sketches.

 

Procedure: Using chart A, lead pupils to give the full meanings of HIV and AIDS. Remove the chart and call
pupils randomly to give the meanings.

 

Using chart B, explain to the pupils that a virus is an infectious agent that is found in virtually all life forms, including humans, animals, plants, fungi, and bacteria. Viruses are not considered free-living, since they cannot reproduce outside of a living cell; they have evolved to transmit their genetic information from one cell to another for the purpose of replication. Viruses often damage or kill the cells that they infect, causing disease in infected organisms. A few viruses stimulate cells to grow uncontrollably and produce cancers.

 

Name the two types of HIV as HIV-1, which is the primary cause of AIDS worldwide, and HIV-2, found mostly in West Africa. Emphasise that the virus attacks the immune system, the body's "security force" that fights off infections. When the immune system breaks down, this protection is lost and can lead to the development of many serious, often deadly infections and cancers. The infections are called "opportunistic infections (OIs)" because they take advantage of the body's weakened defenses. You have heard it said that someone "died of AIDS." This is not entirely accurate, since it is the opportunistic infections that cause death. AIDS is the condition that lets the OIs take hold.

 

Using chart C, explain to the pupils how HIV can be contracted. Most people get HIV by:

 

 

Let pupils know that there are no documented cases of HIV being transmitted by tears or saliva, but it is possible to be infected with HIV through oral sex or in rare cases through deep kissing, especially if you have open sores in your mouth or bleeding gums.

 

Conclude with the discussion on the cure for AIDS that currently, there is no cure for AIDS. There are drugs that can slow down the HIV virus, and slow down the damage to the immune system. But there is no way to get all the HIV out of the body.

 

Assist pupils to develop a simple concept map of the lesson. An example is given below.


 

In this lesson, we learned that

 

·        HIV is the shortened form for Human Immunodeficiency Virus.

·        A virus is an infectious agent that is found in virtually all life forms consisting of two major parts- an outer protective coat called a capsid which is made of protein; and an inside which consists of genetic material- DNA or RNA.

·        HIV mostly infects T-cells, also known as CD4+ cells, or T-helper cells. These cells are white blood cells that turn the immune system on to fight disease. Once inside the cell, HIV starts producing millions of little viruses, which eventually kill the cell and then go out to infect other cells.

·        There are two types of this virus: HIV-1, which is the primary cause of AIDS worldwide, and HIV-2, found mostly in West Africa.

·        AIDS is a shortened form for Acquired Immune Deficiency Syndrome). It is a condition caused by HIV.

·        Most people get the HIV virus by having sex with an infected person; sharing a needle or sharp instruments with someone who's infected; and being born when the mother is infected, or drinking the breast milk of an infected woman.

 

We also learned how to teach the lesson to our pupils using three charts and a concept map.