HIV Infection and AIDS: An Overview


Because early HIV infection often causes no symptoms, a doctor or other health care worker usually can diagnose it by testing a person's blood for the presence of antibodies (disease-fighting proteins) to HIV. HIV antibodies generally do not reach levels in the blood which the doctor can see until one to three months following infection, and it may take the antibodies as long as six months to be produced in quantities large enough to show up in standard blood tests.

People exposed to the virus should get an HIV test as soon as they are likely to develop antibodies to the virus. By getting tested early, they can get the right treatment at a time when their immune systems are most able to combat HIV and thus prevent the emergence of certain opportunistic infections (see Treatment below). Early testing also alerts HIV-infected people to avoid high-risk behaviors that could spread the virus to others.

Most doctors' offices or health clinics can do HIV testing and will usually offer counseling to the patient at the same time. Of course, individuals can be tested anonymously at many sites if they are concerned about confidentiality.

Doctors diagnose HIV infection by using two different types of antibody tests, ELISA and Western Blot. If a person is highly likely to be infected with HIV and yet both tests are negative, a doctor may look for HIV itself in the blood. The person also may be told to repeat antibody testing at a later date, when antibodies to HIV are more likely to have developed.

Babies born to mothers infected with HIV may or may not be infected with the virus, but all carry their mothers' antibodies to HIV for several months. If these babies lack symptoms, a definitive diagnosis of HIV infection using standard antibody tests cannot be made until after 15 months of age. By then, babies are unlikely to still carry their mothers' antibodies and will have produced their own, if they are infected. New technologies to detect HIV itself are being used to more accurately determine HIV infection in infants between ages 3 months and 15 months. A number of blood tests are being evaluated to determine if they can diagnose HIV infection in babies younger than 3 months.


When AIDS first surfaced in the United States, no medicines were available to combat the underlying immune deficiency and few treatments existed for the opportunistic diseases that resulted. Over the past 10 years, however, researchers have developed drugs to fight both HIV infection and its associated infections and cancers.

The Food and Drug Administration has approved a number of drugs for treating HIV infection. The first group of drugs used to treat HIV infection, called nucleoside reverse transcriptase (RT) inhibitors, interrupts an early stage of the virus making copies of itself. Included in this class of drugs (called nucleoside analogs) are AZT (also known as zidovudine or ZDV), ddC (zalcitabine), ddI (dideoxyinosine), d4T (stavudine), and 3TC (lamivudine). These drugs may slow the spread of HIV in the body and delay the onset of opportunistic infections.

Non-nucleoside reverse transcriptase inhibitors (NNRTIs), such as delvaridine (Rescriptor) and nevirapine (Viramune), are also available for use in combination with other antiretroviral drugs.

More recently, a second class of drugs has been approved for treating HIV infection. These drugs, called protease inhibitors, interrupt virus replication at a later step in its life cycle. They include ritonavir (Norvir), saquinivir (Invirase), indinavir (Crixivan), amprenivir (Agenerase), and nelfinavir (Viracept). Because HIV can become resistant to both classes of drugs, combination treatment using both is necessary to effectively suppress the virus.

Currently available antiretroviral drugs do not cure people of HIV infection or AIDS, however, and they all have side effects that can be severe. Some of the nucleoside RT inhibitors may cause a depletion of red or white blood cells, especially when taken in the later stages of the disease. Some may also cause an inflammation of the pancreas and painful nerve damage. Other complications, including lactic acidosis and severe hepatomegaly (enlarged liver) with steatosis (fatty liver) that may result in liver failure and death, have also been reported with the use of antiretroviral nucleoside analogs alone or in combination, including AZT, ddI, ddC, 3TC, and abacavir.

The most common side effects associated with protease inhibitors include nausea, diarrhea, and other gastrointestinal symptoms. In addition, protease inhibitors can interact with other drugs resulting in serious side effects.

Researchers have credited highly active antiretroviral therapy, or HAART, as being a major factor in reducing the number of deaths from AIDS in this country by 47 percent in 1997. HAART is a combination of several drugs to treat patients. These drugs include reverse transcriptase inhibitors and protease inhibitors. Patients who are newly infected with HIV as well as AIDS patients can take the combination.

HAART is not a cure. The health of HIV and AIDS patients has benefited dramatically by combining protease inhibitors with other AIDS drugs, but there are drawbacks. Also, though HIV may not be found in the patients successfully treated with HAART, researchers know that it is still present, lurking in hiding places such as the lymph nodes, the brain, testes, and the retina of the eye.

A number of drugs are available to help treat opportunistic infections to which people with HIV are especially prone. These drugs include foscarnet and ganciclovir, used to treat cytomegalovirus eye infections, fluconazole to treat yeast and other fungal infections, and trimethoprim/sulfamethoxazole (TMP/SMX) or pentamidine to treat Pneumocystis carinii pneumonia (PCP).

In addition to antiretroviral therapy, adults with HIV whose CD4+ T-cell counts drop below 200 are given treatment to prevent the occurrence of PCP, which is one of the most common and deadly opportunistic infections associated with HIV. Children are given PCP preventive therapy when their CD4+ T-cell counts drop to levels considered below normal for their age group. Regardless of their CD4+ T-cell counts, HIV-infected children and adults who have survived an episode of PCP are given drugs for the rest of their lives to prevent a recurrence of the pneumonia.

HIV-infected individuals who develop Kaposi's sarcoma or other cancers are treated with radiation, chemotherapy or injections of alpha interferon, a genetically engineered naturally occurring protein.


Because no vaccine for HIV is available, the only way to prevent infection by the virus is to avoid behaviors that put a person at risk of infection, such as sharing needles and having unprotected sex.

Many people infected with HIV have no symptoms. Therefore, there is no way of knowing with certainty whether a sexual partner is infected unless he or she has repeatedly tested negative for the virus -- and has not engaged in any risky behavior.

People should either abstain from having sex or or use latex condoms, which may offer partial protection, during oral, anal, or vaginal sex. Only condoms made of latex should be used, and water-based lubricants should be used with latex condoms.

Although some laboratory evidence shows that spermicides can kill HIV, researchers have not found that these products can prevent a person from getting HIV.

The risk of HIV transmission from a pregnant woman to her baby is significantly reduced if she takes AZT during pregnancy, labor and delivery, and her baby takes it for the first six weeks of life.


NIAID-supported investigators are conducting an abundance of research on HIV infection, including the development and testing of HIV vaccines and new therapies for the disease and some of its associated conditions. Twenty-eight HIV vaccines are being tested in people, and many drugs for HIV infection or AIDS-associated opportunistic infections are either being developed or being tested. Researchers also are investigating exactly how HIV damages the immune system. This research is suggesting new and more effective targets for drugs and vaccines. NIAID-supported investigators also continue to trace how the disease progresses in different people.

Scientists are investigating and testing chemical barriers, such as topical microbicides, that people can use in the vagina or in the rectum during sex to prevent HIV transmission. They also are looking at other ways to prevent transmission such as controlling sexually transmitted diseases and modifying people's behavior as well as ways to prevent transmission from mother to child.

NIAID, a component of the National Institutes of Health, supports research on AIDS, tuberculosis and other infectious diseases as well as allergies and immunology.

Prepared by:
Office of Communications and Public Liaison
National Institute of Allergy and Infectious Diseases
National Institutes of Health
Bethesda, MD 20892

Public Health Service
U.S. Department of Health and Human Services

May 2000