AIDS overview

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Overview

Acquired immune deficiency syndrome (AIDS) is a collection of symptoms and infections resulting from the specific damage to the immune system caused by the human immunodeficiency virus (HIV) in humans, and similar viruses in other species (SIV, FIV, etc.). The late stage of the condition leaves individuals susceptible to opportunistic infections and tumors. Although treatments for AIDS and HIV exist to decelerate the virus's progression, there is currently no known cure. HIV is transmitted through direct contact of a mucous membrane or the bloodstream with a bodily fluid containing HIV, such as blood, semen, vaginal fluid, preseminal fluid, and breast milk. This transmission can come in the form of anal, vaginal or oral sex, blood transfusion, contaminated hypodermic needles, exchange between mother and baby during pregnancy, childbirth, or breastfeeding, or other exposure to one of the above bodily fluids.

Classification

Since June 5, 1981, many definitions have been developed for epidemiological surveillance such as the Bangui definition and the 1994 expanded World Health Organization AIDS case definition. However, clinical staging of patients was not an intended use for these systems as they are neither sensitive, nor specific. In developing countries, the World Health Organization staging system for HIV infection and disease, using clinical and laboratory data, is used and in developed countries, the Centers for Disease Control (CDC) Classification System is used.

Pathophysiology

Human Immunodeficiency virus causes AIDS by depleting CD4+ T helper lymphocytes. T lymphocytes are essential to the immune response and without them, the body cannot fight infections or kill cancerous cells. Thus the weakened immune system allows opportunistic infections and neoplastic processes. The mechanism of CD4+ T cell depletion differs in the acute and chronic phases, to sum it all AIDS has a complex pathophysiology.

Differentiating AIDS from other Diseases

AIDS is an immunodeficiency disease. It should be considered in patient presenting with symptoms of immunodeficiency. AIDS should be distinguished from congenital disorders and considered in the differential diagnosis of childhood immunodeficiency.

The possibility of HIV infection should be considered on a case-by-case basis and other causes of immune suppression must be considered.

Various medical conditions that cause immunosuppression are chemotherapy, immune disorders, severe combined immune deficiency [SCID], severe malnutrition.

Epidemiology and Demographics

Most researchers believe that HIV originated in sub-Saharan Africa during the twentieth century. It is now a pandemic. In 2007, an estimated 33.2 million people lived with the disease worldwide, and it claimed the lives of an estimated 2.1 million people, including 330,000 children. Over three-fourths of these deaths occurred in sub-Saharan Africa, retarding economic growth and destroying human capital Antiretroviral treatment reduces both the mortality and the morbidity of HIV infection, but routine access to antiretroviral medication is not available in all countries.

HIV/AIDS stigma is more severe than that associated with some other life-threatening conditions and extends beyond the disease itself to providers and even volunteers involved with the care of people living with HIV.

In 2010, an estimated 34 million people were living with HIV, of whom more than 30 million were living in low- and middle-income countries.

Screening

At the end of 2006, an estimated 1,106,400 persons (range: 1,056,400 – 1,156,400) in the United States were living with HIV. CDC estimates that 56,300 new HIV infections occurred in the United States in 2006. About 1 million Americans have HIV — to a surprise, an estimated 25 percent do not know they have the infection. Therefore, HIV screening is important to both extend their lives and prevent further spreading of the disease.

Diagnosis

Laboratory Findings

A number of laboratory tests are important for initial evaluation of HIV-infected paients. Two surrogate markers (CD4 T-cell count (CD4 count), plasma HIV RNA) are routinely used to asses immune function and level of viral viremia.

Electrocardiogram

The pericardium is frequently involved in HIV infections. Also medications used in AIDS therapy can cause EKG changes.

Chest X Ray

Chest X-ray is an extremely common procedure done to evaluate the organs located in the chest area i.e. lungs, heart, and chest wall. It also helps in diagnosing the cause of various symptoms. (for example persistent cough, shortness of breath, chest pain or injury, and fever)

CT

CT scans of chest are important part of diagnosis in HIV patients having pulmonary symptoms. It has an advantage over X-Ray in being more sensitive in detection of early interstitial lung disease, lymphadenopathy, and nodules.

MRI

Magnetic resonance imaging or MRI is used in great deal for the care of HIV-positive patients. MRI is the first-choice among neuroimaging modality in the workup for AIDS dementia complex. An MRI is more sensitive than a head CT in determining if a lesion is truly solitary.

Echocardiography

Patients infected with the human immunodeficiency virus (HIV) have an increased risk of developing heart disease and they may need an echocardiogram.

Treatment

Medical Therapy

The primary goal of antiretroviral therapy (ART) is to reduce HIV-associated morbidity and mortality. This goal is best accomplished by using effective ART to maximally inhibit HIV replication, as defined by achieving and maintaining plasma HIV RNA (viral load) below levels detectable by commercially available assays. Durable viral suppression improves immune function and quality of life, lowers the risk of both AIDS-defining and non-AIDS-defining complications, and prolongs life. Based on emerging evidence, additional benefits of ART include a reduction in HIV-associated inflammation and possibly its associated complications.

Surgery

HIV infected patients may require surgery to treat infections and diseases associated with the condition. Childbirth and organ transplant are two of the many conditions that may require surgery in a HIV patient.

Primary Prevention

There is currently no vaccine or cure for HIV or AIDS. The only known methods of prevention are based on avoiding exposure to the virus or, failing that, an antiretroviral treatment directly after a highly significant exposure, called post-exposure prophylaxis (PEP).

Cost-Effectiveness of Therapy

HIV and AIDS retard economic growth by destroying human capital. Without proper nutrition, health care and medicine that is available in developed countries, large numbers of people are falling victim to AIDS. They will not only be unable to work, but will also require significant medical care. The forecast is that this will likely cause a collapse of economies and societies in the region. In some heavily infected areas, the epidemic has left behind many orphans cared for by elderly grandparents.

Future or Investigational Therapies

Research to improve current treatments includes decreasing side effects of current drugs, further simplifying drug regimens to improve adherence, and determining the best sequence of regimens to manage drug resistance. A number of studies have shown that measures to prevent opportunistic infections can be beneficial when treating patients with HIV infection or AIDS. Vaccination against hepatitis A and B is advised for patients who are not infected with these viruses and are at risk of becoming infected. Patients with substantial immunosuppression are also advised to receive prophylactic therapy for Pneumocystis jiroveci pneumonia (PCP), and many patients may benefit from prophylactic therapy for toxoplasmosis and Cryptococcus meningitis as well.

Daily multivitamin and mineral supplements have been found to reduce HIV disease progression among men and women. This could become an important low-cost intervention provided during early HIV disease to prolong the time before antiretroviral therapy is required. Some individual nutrients have also been tried. Anti-retroviral drugs are expensive, and the majority of the world's infected individuals do not have access to medications and treatments for HIV and AIDS. It has been postulated that only a vaccine can halt the pandemic because a vaccine would possibly cost less, thus being affordable for developing countries, and would not require daily treatments. However, after over 20 years of research, HIV-1 remains a difficult target for a vaccine.