AIDS

Introduction

Previous chapters looked at the human immune system and its components.
A damaged immune system leads to immunodeficiency diseases. AIDS is one of these diseases. This chapter looks at AIDS which stands for Acquired Immunodeficiency Syndrome.

What is AIDS?

Acquired Immunodeficiency Syndrome (AIDS) is a collection of disorders resulting from the destruction of T cells by the Human Immunodeficiency Virus (HIV). During the late stage of this disease an organism is very prone to opportunistic infections (infections caused by organisms that normally do not cause disease) and tumours (abnormal growth of an organ's tissue). Today, AIDS is still an incurable and fatal disease.

HIV

HIV is a retrovirus. It is the type of virus that, when not infecting a cell, stores its genetic information on a single-stranded RNA molecule instead of the double-stranded DNA. After a retrovirus penetrates a cell, it constructs a DNA version of its genes. This DNA then becomes part of the infected cell's genetic material. HIV is a 'slow' type of virus that falls into the category of lentiviruses. Lentiviruses are called slow viruses because they take a long time to cause damage to the body. See image 1.

It is hard to believe but HIV is actually a very fragile organism. If HIV is outside the body, its capsid disintegrates very quickly which instantly 'disarms' the virus. That is why infection is virtually impossible without direct blood-to-blood contact or through the mixing of body fluids containing the virus.

Once inside the body, HIV starts replicating within T cells called T helpers or Th. T helpers are responsible for the 'danger' signal transmission to the antibody-producing B cells. The infected organism's Th cell count gradually falls, which leads to the shut down of the immune system.

Sometimes HIV-affected people can live for many years if their body is able to replace these destroyed Th cells. When their Th cell count falls below a critical threshold, they start to display symptoms of AIDS. Technically, HIV infected people do not die from AIDS. They die because their damaged immune system makes them susceptible to a wide range of infections that are generally harmless to healthy people. See image 2.

See animation 1.

AIDS origin

The HIV virus has not been around for long. It is quite a young virus. The first recognised cases of AIDS occurred in the USA in the early 1980s. A number of gay men in New York and San Francisco suddenly began to develop rare opportunistic infections and cancers that were resistant to any treatment. It quickly became obvious that all infected people were suffering from a common syndrome - their immune systems were severely damaged.

According to all scientific research results, it seems highly likely that Africa was the place where the transfer of HIV to humans first occurred. Monkeys from Asia and South America have never been found to have the HIV forerunner - SIV (Simian immunodeficiency virus).

The 'hunter' theory

The most commonly accepted theory is the 'hunter' theory implying that the virus was transferred to humans as a result of chimpanzees being killed and eaten, or their blood penetrating cuts or wounds on the hunter. A viral transfer between animals and humans is called zoonosis.

AIDS pandemic

The outbreak of an infectious disease over large geographical areas is called a pandemic. Because of the number of people killed by the HIV virus, AIDS is sometimes called 'The plague of the 20th Century'. At the moment, the continent of Africa has the largest HIV-affected population. Countries like Russia are catching up fast.

There are a number of factors that have contributed to the spread of HIV, most of which occurred in the latter half of the twentieth century.

Travel
Blood industry
Drug use

See image 3.

HIV prevention

Sexual contact remains the most common form of HIV transmission globally. But the easiest way for HIV to spread is through sharing hypodermic needles. Hypodermic needles are syringe needles used for injections beneath the upper skin layer, epidermis.

For each type of transmission there are things that an individual can do to reduce or eliminate the risk. They are the following:

Sex education for young people is an essential part of HIV prevention. This should include accurate and explicit information about how to practise safer sex.
The safety of medical procedures and other activities that involve contact with blood, such as tattooing and circumcision, can be improved by routinely sterilising or disposing of equipment
HIV can be transmitted from a mother to her baby during pregnancy, labour and later through breastfeeding. The first step towards reducing the number of HIV-infected babies is to prevent unwanted pregnancies and the HIV infection in women.

HIV treatment

A cure for AIDS has not yet been discovered. There are, however, treatments that can stop people from becoming ill for many years. The treatment consists of drugs that have to be taken every day for the rest of the infected person's life. These drugs slow down the replication of HIV in the body. These drugs are often referred to as: