What Is It?

The human immunodeficiency virus (HIV) weakens the body’s immune defenses by destroying CD4 (T-cell) lymphocytes, which are a group of white blood cells that normally help guard the body against attacks by bacteria, viruses and other germs. When HIV destroys CD4 lymphocytes, the body becomes vulnerable to many different types of infections. These infections are called opportunistic because they have an opportunity to invade the body when the immune defenses are weak. HIV infection also increases the risk of certain cancers, illnesses of the brain (neurological) and nerves, body wasting and death. The entire spectrum of symptoms and illnesses that can happen when HIV infection significantly depletes the body’s immune defenses is called acquired immunodeficiency syndrome or AIDS.

Since 1981, when HIV/AIDS was first recognized as a new illness, scientists have learned much about the HIV infection process. HIV is spread through contact with an infected person’s body fluids, especially through blood, semen and vaginal fluids. Once inside the body, HIV particles invade CD4 lymphocytes and use the cells’ own genetic material to produce billions of copies. For newly manufactured HIV particles to enter the bloodstream and infect more CD4 cells, they first burst (or lyse) the infected CD4 cell. This allows the cycle of HIV infection to continue. The total number of normal CD4 cells decreases progressively from the time someone is infected with HIV.

Eventually, the number of CD4 cells drops below the threshold level needed to defend the body against opportunistic infections, and the person develops AIDS. Doctors used to think that HIV was dormant or latent during the time between the initial infection and the diagnosis of AIDS. We now know that HIV is active, replicating and killing CD4 cells from the time the infection starts through and beyond the diagnosis of AIDS.

Within the past two decades, about 40 million people worldwide have become infected with HIV. Approximately 12 million have died. More than 90 percent of these people live in developing countries. In some parts of Africa, more than half of adult deaths are caused by HIV infection, leaving millions of children orphaned after their mothers died of AIDS. In the United States, as of mid 1997, there were more than 612,000 cases of AIDS reported, with almost 380,000 deaths, including 4,600 children. HIV rates are increasing most rapidly among minority populations. The infection occurs six times as often in African-Americans and three times as often in Hispanics compared with whites.


In its early stages, HIV infection has no symptoms or causes only a flu-like illness with many of the following symptoms: fever, sore throat, rash, nausea and vomiting, diarrhea, fatigue, swollen lymph nodes, muscle aches, headaches and joint pain. Although 50 percent to 90 percent of people experience symptoms within the first few weeks of contracting HIV infection, most people and doctors dismiss the illness as a routine cold or flu. In a small number of cases, this early stage of infection may progress to meningitis (inflammation of membranes covering the brain) or other severe flu-like symptoms that require hospitalization.

As the destruction of CD4 cells causes them to drop below normal (normal is 800 to 1,200 cells per cubic millimeter of blood), the person may begin to develop swollen lymph nodes and abnormalities of the skin, such as seborrheic dermatitis (dandruff), new or worsening psoriasis and minor infections. Ulcers around the mouth can develop.

Over the next few years, as the CD4 level continues to drop, the frequency of skin problems and mouth ulcers increases. Recurrent herpes and varicella-zoster infections (shingles) can occur. Many people develop diarrhea, fever, unexplained weight loss, joint and muscle pain and fatigue. Old tuberculosis infections may reactivate even before AIDS develops. (Tuberculosis is one of the most common AIDS related infections in the developing world.)

Finally, with further decreases in CD4 levels, the person develops AIDS. In an HIV infected person, some signs that AIDS has developed are:

  • The CD4 count has decreased to 200 cells or below.
  • An infection has developed, causing certain types of pneumonia, diarrhea, eye infections or meningitis. Some of the germs that can cause these opportunistic infections include Candida fungus, cryptococcosis, cytomegalovirus, herpes simplex virus, Mycobacterium avium complex and Pneumocystis carinii. Additionally, fungal infections specific to certain areas of the U.S., such as histoplasmosis and coccidioidomycosis, can occur.
  • A tumor has developed, including cervical cancer, Kaposi’s sarcoma (cancer causing round, reddish spots in the skin and mouth), non-Hodgkin’s lymphoma (certain types) or brain lymphoma.
  • An AIDS related brain illness has developed, including HIV encephalopathy (AIDS dementia) or progressive multifocal leukoencephalopathy.
  • There is severe body wasting (HIV wasting syndrome).
  • There is an AIDS related lung illness, such as pulmonary lymphoid hyperplasia or lymphoid interstitial pneumonia (usually seen only in children).


Your doctor will ask about possible HIV risk factors, such as previous sexual partners, intravenous drug use, blood transfusion and occupational exposure to blood. Your doctor will ask about a variety of symptoms, such as fever, weight loss, muscle and joint aches, fatigue and headache, and about medical problems you may have had, such as skin rashes or infections, sinusitis, Pneumonia and yeast infections. This typically is followed by a complete physical examination. Your doctor will look for a thick white coating on your tongue that may represent thrush (a sign of infection with Candida fungus), skin abnormalities such as Kaposi’s sarcoma or recurrent infections and other abnormalities that suggest the diagnosis of AIDS.

HIV testing can be done in your doctor’s office, in an anonymous clinic or with at home. Your doctor will confirm the diagnosis of HIV infection through blood tests. The initial screening test is called enzyme linked immunosorbent assay (ELISA). It detects disease fighting proteins in your immune system (antibodies) specific to HIV. A Western blot test, which also measures the body’s response to HIV, is performed to more accurately confirm the infection. Neither the ELISA nor Western blot is accurate immediately after exposure. It can take a few months for these tests to become positive.

The period between infection with HIV and the development of positive test results on ELISA and Western blot is called the window period. This term refers to the window of time between getting the HIV infection and the ability to detect the body’s response to infection with one of these two tests. If the test results are positive, another test, called the HIV RNA blood test, can measure the amount of HIV virus in the blood (viral load). To confirm the diagnosis of AIDS, your doctor will order a blood test for CD4 cell count. A count less than 200 cells indicates AIDS. You may also undergo tests to diagnose AIDS related conditions, including opportunistic infections, brain illness, a tumor, body wasting or lung illness, depending on the symptoms.

Expected Duration

Because there is currently no cure, HIV infection is a lifelong illness.


HIV infection can be passed from person to person in any of the following ways:

  • Unprotected sexual intercourse (heterosexual or homosexual)
  • Oral sex with an infected person
  • A contaminated blood transfusion (very rare in the U.S. since 1985, when HIV blood testing began)
  • Needle sharing (if one intravenous drug user is infected)
  • Occupational exposure (needle stick with infected blood)
  • Artificial insemination with infected semen
  • Organ transplant taken from an HIV infected donor

Newborns can catch HIV infection from their mothers before birth or through breastfeeding.

There is no evidence that HIV can be spread through the following: kissing; sharing food utensils, towels or bedding; swimming in pools; using toilet seats; using telephones; or having mosquito or other insect bites.

Although several HIV vaccines are being tested, none has been approved. You can decrease your chances of acquiring HIV infection by avoiding high-risk behaviors. To decrease the risk of HIV infection:

  • Practice sexual abstinence, have sex with only one partner who is also committed to having sex with only you (a monogamous relationship) or use barrier methods of contraception such as condoms.
  • Intravenous drug users should never share needles.
  • If you are a health care worker, strictly follow universal precautions (the established infection-control procedures to avoid contact with bodily fluids).
  • If you are a woman thinking about becoming pregnant, have a test for HIV beforehand, especially if you have a history of behaviors that put you at risk of HIV infection. Pregnant women who are HIV-positive need special prenatal care and medications to decrease the risk that HIV will pass to their newborn babies.


After checking the level of active HIV infection (by measuring plasma HIV RNA) and checking CD4 cell counts (to determine the amount of immune system damage), your doctor may choose a combination of drugs to fight HIV infection. These drugs are called antiretroviral. By using several drugs simultaneously (often called a drug cocktail), your doctor hopes to increase the effectiveness of AIDS treatment by attacking HIV at multiple points. Combining drugs also limits the risk that HIV will become resistant (and therefore ineffective) to drugs.

Many studies have shown that people with high levels of HIV RNA in the blood will progress more rapidly to AIDS, and that the destruction of CD4 cells is speed up by larger numbers of viral copies (the viral load). The ultimate goal is to suppress HIV RNA to undetectable levels on blood tests. Currently available antiretroviral drugs include:

  • Nucleoside analogs — such as zidovudine (Retrovir, AZT), didanosine (Videx, ddI), zalcitabine (HIVID, ddC), stavudine (Zerit, d4T), abacavir (ABC) and lamivudine (Epivir, 3TC). There is a combination pill called Combivir, which contains lamivudine and zidovudine.
  • Protease inhibitors — such as saquinavir (Invirase, Fortovase), ritonavir (Norvir), indinavir (Crixivan), nelfinavir (Viracept)
  • Non-nucleoside reverse transcriptase inhibitors — such as nevirapine (Viramune), delavirdine (Rescriptor) and efavirenz (Sustiva)

One common treatment approach is HAART (highly active antiretroviral therapy), which combines three nucleoside analogues, two nucleoside analogues and one protease inhibitor, or two nucleoside analogues and one non-nucleoside reverse transcriptase inhibitor. Many other variations exist. It is important to note that many of these drugs have side effects, such as nausea and diarrhea. In addition, some have severe drug interactions with commonly used medications.

The U.S. Food and Drug Administration (FDA) has approved more than 22 drugs for treating AIDS related conditions, including drugs that fight opportunistic infections and Kaposi’s sarcoma. In addition to these medications, people with low CD4 counts should take certain medications to prevent the development of opportunistic infections. For example, people should take trimethoprim-sulfamethoxazole (Bactrim) if their CD4 count is less than 200.

Treatment scams for AIDS rob trusting people of up to $10 billion annually. To fight these scams, the FDA formed the AIDS Health Fraud Task Force in 1989. Based on results of FDA investigations, some unapproved therapies to avoid are “energized” water, “ozone therapy” and the hydrogen-peroxide “treatment.”

When To Call A Professional

Call your doctor if you believe that you have been exposed to the infected body fluids of someone who has HIV or AIDS. If you test yourself for HIV at home, call your doctor immediately if your result is positive. Even if your result is negative, speak with your doctor about your concerns, questions, HIV prevention or the need for follow up testing.


The average time for HIV infection to progress to AIDS is 10 to 11 years — if the person does not use antiviral medication or if just one antiviral drug (monotherapy) is used. However, in about 20 percent of people with HIV infection, usually those with the highest viral load, AIDS develops sooner (five years after infection). In 2 percent of people it develops later (more than 12 years after infection).

Once HIV infection has progressed to AIDS, there is an increased risk of death that varies dramatically from person to person. For example, some people with AIDS have died shortly after they were diagnosed, whereas others have lived 12 years or more. Since the FDA approved newer antiretroviral drugs in 1995, the number of deaths from AIDS has decreased dramatically in the U.S. The rate of AIDS hospitalizations and complications also declined.

Johns Hopkins patient information

Last revised:

Diseases and Conditions Center

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All ArmMed Media material is provided for information only and is neither advice nor a substitute for proper medical care. Consult a qualified healthcare professional who understands your particular history for individual concerns.