Difference between HIV and AIDS | Stages of HIV | Testing for HIV
What is an "Opportunistic Infection"? | Why treat HIV? | How is HIV treated?
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Difference between HIV and AIDS
HIV (Human Immunodeficiency Virus) is a virus that attacks the immune system
and damages it. A damaged immune system cannot fight germs well.
There are many stages during the HIV infection. AIDS is an advanced HIV stage.
AIDS stands for Acquired Immunodeficiency Syndrome. "Acquired" means
that it is given by someone else as opposed to being something that just happens.
"Immunodeficiency" means that the immune system is weak. "Syndrome"
means a group of conditions.
AIDS is diagnosed when the immune system is weak, as shown by a CD4 count of less than 200 cells/milliliter, or by the presence of certain opportunistic infections (for example, pneumocystis carinii pneumonia, and fungal infection of the esophagus), tumors or wasting. AIDS is the condition that results from HIV after it has done significant damage to the immune system.
A person who is HIV positive (meaning a person who has HIV) does not necessarily have AIDS, but a person who has AIDS is HIV positive. If a person has been diagnosed with AIDS as some point in their lives, the diagnosis of AIDS as opposed to HIV positive alone will remain even if there is a significant improvement in their health status.
The course of HIV varies greatly from one person to another. When untreated, the average time from transmission of HIV to death is 10 to 11 years. It can be shorter or longer. The main stages from transmission to advanced disease in an untreated person are:
- Stage 1: Primary HIV Infection
- Stage 2: Asymptomatic chronic infection
- Stage 3: Symptomatic HIV infection
- Stage 4: Advanced HIV Infection
Shortly after the transmission of HIV from one person to another, CD4 cells get destroyed. HIV multiplies itself at a rate of 10,000,000,000 virions per day. As a result, while the amount of virus in the blood increases, the amount of CD4 cells decreases. This initial stage is called "Primary HIV Infection". It is often characterized by flu-like signs and symptoms like fever, sore throat, swollen glands and cough. These signs and symptoms usually last a few weeks, but only about 20% of people will see a doctor because of them. Thus, the diagnosis is often missed during that stage.
It is also during the stage of "Primary HIV Infection" that the immune system tries to fight HIV and starts developing antibodies. The development of antibodies against HIV is called "seroconversion". Time to seroconversion is around 21 to 90 days. Periods of greater than 6 months to seroconversion have been reported. The tests that are used to diagnose HIV detect the presence of antibodies in the blood. An HIV test can, therefore, be negative (i.e., show that a person does not have HIV) if it is done before the body has had enough time to produce enough antibodies for the test to detect. This is why there is a 3-month period necessary between the time of transmission and the time the test is done, for the test to be accurate.
The next stage is called "Asymptomatic Chronic Infection". During this stage, people don’t feel sick, but the virus continues to attack and destroy the immune system. HIV can also become harder to treat. This stage usually lasts several years. Starting treatment against HIV prolongs that stage so that people live longer and healthier.
The following stages are called "Symptomatic Infection" and "Advanced Stage". During these stages, the body’s immune system is too weak to fight infections that would normally be easily fought. The infected person becomes very sick. Other health problems may also develop. Several types of problems can happen to the lungs, the skin, the nerves and the digestive system. In the "Advanced stage", the body looses the fight to opportunistic infections, tumors, wasting, and neurological complications.
To fight HIV, the body produces antibodies against it. There are different ways to detect HIV, but the most common one is by detecting the presence of antibodies against HIV in the blood.
In order to work, the test must be done 3 months or more after the time
of transmission of HIV. This is because it may take 3 months for the body
to produce enough antibodies that can be detected by the test. A test that
shows the absence of antibodies may be because the person does not have HIV,
or because there are not enough antibodies in the blood at the time the test
was done to detect them. In this latter case, another test should be done
later.
There are now 2 tests available to detect HIV. The first test is done with
a blood sample, and it takes about 2 weeks to get the results. If the test
is negative (i.e., the results show that a person does not have HIV), it may
be because the person does not have HIV or because there are not enough antibodies
at that time in the blood for the test to detect.
There is a new test called "Rapid testing" or "Point of care testing" that gives preliminary results in 15 minutes, and only requires a drop of blood. Once again, if this test is negative, it may be because the person is not infected, or because the person got infected less than 3 months ago. If the test is positive, further testing that will take an additional 2 weeks will be necessary before a diagnosis is made.
What is an "Opportunistic Infection"?
An opportunistic infection is an infection that develops in people with a damaged immune system. Germs such as fungus, parasites, bacteria and viruses constantly attack the body, and are normally easily fought by a healthy immune system. If, however, the immune system is damaged, the germs take advantage of the immune system, hence the term "opportunistic", and bring on an infection.
The number of possible opportunistic infections increases as the immune system becomes damaged (as indicated by a decreasing CD4 count).
Can Opportunistic Infections be prevented ?
Opportunistic infections can be prevented with medications against opportunistic
infections (see below : Information Sheets), and by strengthening the immune
system with antiretroviral agents.
Other measures may also help. These include avoiding eating raw or uncooked
meat; washing hands after contact with raw meat and soil (gardening); washing
fruit and vegetables before eating them raw; and washing hands thoroughly
after changing a cat litter box.
Although there is currently no cure for HIV, it can be treated. There are many reasons for treating HIV. Treating HIV:
- slows down its progression
- prolongs life
- improves the quality of life
- decreases the reproduction of HIV
- prevents or reverses a damaged immune system
HIV adapts very quickly and becomes resistant to a drug or a drug class when only one drug is used. It is, therefore, important to use several drugs against HIV at the same time. This way, it is more difficult for HIV to become resistant to the drugs.
Although there are many different drugs that can be taken together, not all combinations of drugs work. In fact, when certain drugs are taken together, they can cancel each other out or increase each other’s side effects.
Types of antiretroviral drugs and how they work
The drugs used to treat HIV are called "antiretrovirals". There are currently 15 antiretrovirals commercially available. They belong to one of 3 main types or classes of antiretrovirals, depending on how they attack the virus:
- the nucleoside reverse transcriptase inhibitors, also called "NRTIs" or "Nukes"
- the non-nucleoside reverse transcriptase inhibitors, also called the "NNRTIs" or "non-Nukes"
- the protease inhibitors - also called the "PIs"
- the fusion inhibitor - also called the entry inhibitor
The way they attack HIV is by preventing it from reproducing itself. The
three types of antiretrovirals do this in a different way during the lifecycle
of HIV.
The lifecycle of HIV can be divided into many steps. The reverse transcriptase is a protein necessary for HIV to reproduce itself. It plays an important role at the beginning of the lifecycle of HIV. The NRTIs (or Nukes) and the NNRTIs (or non-Nukes) interfere with the reverse transcriptase, but in different ways. The PIs interfere with a different enzyme called protease, which is essential at the end of the lifecycle of HIV. When a person takes these drugs, HIV has a very hard time reproducing itself because essential enzymes do not work properly. The fusion inhibitor works by preventing entry of the virus into the cell.
English Version - The Glossary of HIV/AIDS-Related Terms 5th Edition
Spanish version -The Glossary of HIV/AIDS-Related Terms 5th Edition
