AIDS (acquired immunodeficiency syndrome) is the most severe stage of the infection caused by the human immunodeficiency virus (HIV). According to the WHO (World Health Organization), AIDS is the fourth and final stage of HIV infection (WHO stage 4) marked by the presence of potentially life threatening and otherwise rare infections and cancers which arise since the body’s immune defenses are almost totally compromised. These infections are referred to as opportunistic infections because it is only when the body’s immunity drops to a certain point that it can manifest and persist.
AIDS is the most serious health hazard of the 21st century. More than 35 million people around the world are believed to be living with HIV at present. However, these estimates may be conservative as the stigma associated with HIV/AIDS and ignorance about the disease has often hampered screening programs and affected epidemiological efforts. Nevertheless, it is also one of the greatest barriers to economic and social development in countries where large populations are affected by the disease.
Difference from HIV
A person infected with HIV usually has mild symptoms or sometimes none at all. The immune system is still able to overcome infections to a large degree although not as efficiently. This is dependent on the level of a certain type of immune cell known as CD4+ T-lymphocytes. Therefore the person is termed “HIV positive”. When the level of CD4+ T-cells drops below 200 cells/mm3, it is termed as AIDS and no longer being just HIV positive.
The presence of certain diseases which are not otherwise seen in a person with a normal immune system is also an indication of AIDS, irrespective of the CD4 cell count. These diseases are therefore known as AIDS-defining illnesses. AIDS should not be viewed as a different condition from HIV infection but rather a another stage in the progressions of HIV infection – the final stage. An HIV positive does not automatically have AIDS but it is inevitable, within years or decades, depending on the management of HIV infection.
Causes of AIDS
Picture of the virus (green) on
the surface of white blood cells
from CDC.gov website
AIDS is caused by the HIV virus. The virus on entering the body multiplies in the immune cells (mainly the CD4 T-lymphocytes). The lymphocytes are destroyed as the virus multiplies within it thereby releasing many HIV particles into blood. Each HIV particle can infect a new lymphocyte and repeat the cycle. Over a period of time, the continuous destruction of lymphocytes leads to a fall in the CD4 T-cell counts below the critical level that is needed to maintain its protective capability. This predisposes the infected person to opportunistic infections and cancers. Read more on HIV cancers.
HIV is spread mainly through blood and other body fluids like semen and vaginal secretions. It is in a high risk situation where a non-infected individual is exposed to the body fluids of an infected person that HIV transmission occurs. Important risk factors are :
- Sexual contact with an HIV infected individual is the most important risk factor and accounts for the main mode of HIV transmission globally. High risk situations include :
- Unprotected sex
- Wounds over the genital areas
- Aggressive and unnatural sexual practices that can cause wounds
- Having multiple sexual partners
- Visits to professional sex workers
- Contact with blood through transfusions, sharing of needles among IV drug users and needle-stick injuries in health care workers.
- Mother-to-child transmission (MCT) during pregnancy, at the time of delivery or while breastfeeding.
The symptoms of the different stages of HIV and of AIDS is dependent on several factors, including the person’s general state of health, nutrition and lifestyle, CD4 cell count and the presence of opportunistic infections or cancer. Acute HIV infection features can develop within the first few weeks of HIV infection. The symptoms here may include :
- generalized weakness
- skin rashes
- muscle aches and joint pains
- sore throat
- lymph node enlargement
- ulcers in the mouth and esophagus
This stage will be followed by latent phase wherein patients do not have any symptoms. The latent phase may extend from several months to around 20 years. The lack of symptoms does not indicate that the infection has resolved or stagnated. There is a gradual progression towards AIDS and the decline of the CD4 T-cell count and rise of the viral load (amount of virus particles in the blood) indicates this progression.
AIDS is characterized by generalized symptoms like :
- recurrent fever with chills
- unexplained diarrhea lasting more than one month
- unintentional weight loss
These symptoms are non-specific meaning that it does not clearly indicate that a person has AIDS and can be seen with several other disease including other types of infections and cancer. AIDS patients also suffer from a wide variety of opportunistic infections, the symptoms of which are more specific. AIDS defining illnesses include :
- Candidiasis (thrush) of the esophagus
- Cerebral lymphoma, primary
- Coccidiodomycosis, extrapulmonary
- Cryptococcal meningitis
- CNS toxoplasmosi
- Cytomegalovirus (CMV) infection (retinitis, colitis and/or other organs)
- Dementia, HIV associated
- Mycobacterium avium intracellulare, disseminated
- Histoplasmosis, extrapulmonary
- Invasive cervical cancer
- Kaposi sarcoma
- Leukoencephalopathy, progressive multifocal
- Non-Hodgkin lymphoma
- Pneumocystis pneumonia
- Salmonella bacteremia, recurrent non-typhoidal
- Tuberculosis, pulmonary (lung) or extrapulmonary
- Wasting (cachexia), HIV associated
What does AIDS look like?
There is no specific appearance of AIDS. Some AIDS patients may appear otherwise healthy while others are severely ill. Even the presence of AIDS-defining illnesses is not always a sign of HIV and AIDS. Many of these infections and cancers categorized as AIDS-defining illnesses can occur in a person without HIV (HIV seronegative) but it is often uncommon in these individuals. Therefore these illnesses can only be considered as AIDS-defining illnesses when a person has already been tested and diagnosed with HIV.
Similarly, a person living with HIV who looks healthy should not assume that the AIDS stage has not as yet been reached. Frequent immune monitoring is necessary. Once the CD4 count drops to levels below 200 cells/mm3, an HIV positive person has AIDS irrespective of how they look or whether they have opportunistic infections and HIV cancers. Therefore it is important that opportunistic infections and cancers particularly of the skin and eye should not be assumed to be a feature of AIDS without proper medical assessment.
Screening for HIV infection is done by ELISA test and the confirmation is usually done by the Western Blot test. Treatment is generally based on the CD4 cell count. Viral RNA load in the blood is also tested in some patients to monitor the progression of the disease by the multiplication of the virus over time.
The treatment of HIV infected patients is initiated when the CD4 lymphocyte counts fall below 200 cells/mm3 although newer guidelines advocate commencing treatment at levels below 350 cells/mm3. There is no treatment that can completely cure AIDS at present although virus-combating drugs known as antiretrovirals (ARVs) has helped increase the lifespan of AIDS patients. Treatment is aimed at :
- suppressing the virus
- reducing the viral load
- increasing the CD4 count above 200
- reducing opportunistic infections
The treatment of AIDS is usually using combination therapy against the virus referred to as ‘highly active antiretroviral therapy’ (HAART). This therapy includes combination of :
- one of the protease inhibitors (like ritonavir, lopinavir etc) or one of the non-nucleoside reverse transcriptase inhibitor (like efaviranz, nevirapine), and
- two nucleoside reverse transcriptase inhibitor (like zidovudine, lamivudine)
Newer drugs like entry inhibitors or HIV integrase inhibitors may also be included in the combination therapy. Other main aspects of treatment of AIDS patients is prophylaxis against opportunistic infections and treatment of complications related to HIV.
Article reviewed by Dr. Greg. Last updated on April 18, 2012