HIV stands for Human Immunodeficiency Virus. It is the virus that causes AIDS. A member of a group of viruses called retroviruses, HIV infects human cells and uses the energy and nutrients provided by those cells to grow and reproduce.

How is HIV transmitted?

A person who has HIV carries the virus in certain body fluids, including blood, semen, vaginal secretions, and breast milk. The virus can be transmitted only if such HIV-infected fluids enter the bloodstream of another person.

HIV must get into the bloodstream. It is not enough to be in contact with an infected fluid for HIV to be transmitted. Healthy, intact skin does not allow HIV to get into the body.

HIV can enter through an open cut or sore, or through contact with the mucous membranes. Transmission risk is very high when HIV comes in contact with the more porous mucous membranes in the genitals, the anus, and the rectum, which are inefficient barriers to HIV. Transmission is also possible through oral sex because body fluids can enter the bloodstream through cuts in the mouth.

Paths of Infection - HIV can be transmitted through:
1. Unprotected vaginal, anal and oral sex
2. Direct blood contact, which may occur through needle sharing, transfusions, accidents in health care settings, or certain blood products
3. Mother to baby; before or during birth or through breast milk

Is there a vaccine to prevent HIV infection?

Despite continued intensive research, experts believe it will be at least a decade before we have a safe, effective, and affordable AIDS vaccine. And even after a vaccine is developed, it will take many years before the millions of people at risk of HIV infection worldwide can be immunized. Until then, other HIV prevention methods, such as practicing safer sex and using sterile syringes, will remain critical.

How do I know if I’m infected?

Immediately after infection, some people may develop mild, temporary flu-like symptoms or persistently swollen glands. Even if you look and feel healthy, you may be infected. The only way to know your HIV status for sure is to be tested for HIV antibodies-proteins the body produces in an effort to fight off infection. This usually requires a blood sample. If a person's blood has HIV antibodies, that means the person is infected.

The stages of HIV infection

The mechanism and stages of infection

HIV infects immune system cells and cells of the central nervous system. The main cell that HIV infects is called the 'T helper' lymphocytes. This type of T lymphocytes is crucial cells of our immune (defense) system for coordinating all the other immune cells, and any damage or loss of T helper cells seriously impairs the immune system.

HIV infects the T helper cell because it contains on its surface CD4 protein which is necessary for HIV to infect a cell. T helper cells are therefore also known as CD4 lymphocytes.

Once it enters the T-helper cell, HIV takes control of it and begins to replicate (reproduce), and infected T-helper cells die in a few days. New viruses then look for a new T-helper cell to infect and replicate the entire process while, on the other hand, immune system rapidly kills HIV and HIV-infected cells, and replaces the T-helper cells that are destroyed.

HIV progression can generally goes through four distinct phases:
1. primary infection
2. clinically asymptomatic stage
3. symptomatic HIV infection
4. Progression from HIV to AIDS.

PHASE 1: Primary HIV Infection

The initial phase of the infection may be completely absent in many people. In the case of about 20% of those infected, it occurs immediately after the transmission of the infection, lasts for several weeks and has symptoms similar to a flu, which is sometimes called a seroconversion illness. After that the immune system begins to respond to a large amount of HIV in the peripheral blood by producing antibodies to the virus and cytotoxic lymphocytes.

At this stage, when the test results for antibodies to HIV (ELISA test), may be falsely negative.

PHASE 2: Clinical asymptomatic phase

The duration of this phase is individual, although the average is about 10 years. As its name suggests, is has no symptoms, but sometimes swollen glands may be present.

The amount of virus in peripheral blood drops to a very low levels, but the HIV antibodies are detectable in the blood.

Researchs show that during this phase, the virus is extremely active in the lymph nodes. Large amounts of T-helper cells are infected and die, and large amounts of virus is produced.

It is a new kind of test that measures small amounts of HIV to flee from the lymph nodes. This test, which measures HIV RNA (genetic material) is called a test of the virulence of HIV (viral load test) and has an increasing role in the treatment of HIV infection.

PHASE 3: Symptomatic HIV Infection

Over time the immune system loses the struggle and it is no longer able to contain HIV, which occurs due to three main reasons:
• The lymph nodes and tissues become damaged or depleted due to years of activity;
• HIV mutates and becomes more pathogenic, in other words, it becomes stronger and more diverse, leading to increased destruction of T-helper lymphocytes;
• The body is no longer able to keep up with replacing the T-helper cells that are destroyed and their number is rapidly decreasing.

Immune system fails and there are first signs of illness. Initially, symptoms are mild, with a further deterioration of the immune system; symptoms can get worse and become more difficult.

Where do opportunistic infections and cancers occure?

Symptomatic HIV infection is characterized by the appearance of opportunistic infections and cancers that would normaly be prevented by a healthy immune system. These diseases can occur in almost entire body and the most common examples are shown in the table below.

As the table indicates, symptomatic HIV infection includes multi-system diseases. The resulting disease or cancers are treated, but the real underlying cause is the HIV, and he continues to weaken the immune system allowing new diseases to appear. If the virus does not slow down the symptoms of immune suppression will continue to deteriorate.

Examples of the infection / tumor

The respiratory system
Pneumocystis carinii pneumonia (PCP), tuberculosis (TB), Kaposi's sarcoma (KS)

Gastro-intestinal tract
Cryptosporidioza, Candida, Cytomegolavirus (CMV), Isosporiasis, Kaposi's Sarcoma

Central / peripheral nervous system
Cytomegolavirus, Toxoplasmoza, Cryptococcosa, Non-Hodgkin lymph, Varicella Zoster, Herpes simplex

Herpes simplex, Kaposi's sarcoma, Varicella Zoster

STAGE 4: Progression from HIV infection to AIDS

As the immune system becomes more and more damaged the illnesses become more severe leading eventually to the diagnosis of AIDS.

AIDS diagnosis is confirmed when a person develops one or more serious opportunistic infections or tumors.

People can become very sick from HIV and still not develop AIDS.

Basic information on treatment

Twenty drugs have been approved to treat individuals infected with HIV. They are called antiretroviral drugs because they attack HIV, which is a retrovirus

After entering the host cell, HIV uses specific enzymes to survive and multiply. The first approved classes of antiretroviral drugs work by interfering with the virus' ability to use these enzymes. These drugs fall into two categories.

Reverse transcriptase (RT) inhibitors - RT inhibitors interfere with an enzyme called reverse transcriptase that HIV needs to make copies of itself. There are two main types of RT inhibitors, and they each work differently.

Protease inhibitors (PI) - Protease inhibitors interfere with the protease enzyme that HIV uses to produce infectious viral particles
The newest class of antiretroviral drugs works by changing the shape of the outer covering of the HIV virus. This class of drugs is called fusion inhibitors. Fusion inhibitors interfere with the virus' ability to fuse with the cellular membrane, thereby blocking entry into the host cell.

Currently available drugs do not cure HIV infection. They can suppress HIV but are unable to completely eliminate it from the body. Because HIV can become resistant to any one drug, people with HIV infection must take a combination of antiretroviral drugs to suppress the virus. The combination of drugs, usually from at least two classes, is referred to as highly active antiretroviral therapy (HAART).

Although the use of HAART has greatly reduced the number of deaths due to HIV, this powerful combination of drugs cannot suppress the virus completely. People infected with HIV who receive antiretroviral drugs can still transmit HIV to others through unprotected sex and needle sharing.

People with HIV take medicines with complicated regimens, often taking several drugs per day and some of which may require fasting. Hence, some people may have difficulty adhering to these complicated regimens, find the food restrictions difficult to deal with, and may experience unpleasant side effects such as nausea and vomiting.

Aside from the complicated dosing regimens, antiretroviral drugs themselves may cause medical problems. Metabolic changes can occur in people with HIV taking antiretroviral drugs. They may include abnormal fat distribution, abnormal lipid and glucose metabolism, and bone loss.