HIV infection is a condition caused by the human immunodeficiency virus (HIV). The condition gradually destroys the immune system, which makes it harder for the body to fight infections.

This article provides a general overview. For more detailed information, see:

• AIDS
• Acute HIV infection
• Asymptomatic HIV infection
• Early symptomatic HIV infection

Human immunodeficiency virus infection

The human immunodeficiency virus (HIV) can be spread by the following:

• Through sexual contact -- including oral, vaginal, and anal sex
• Through blood -- via blood transfusions (now very rare in the U.S.) or needle sharing
• From mother to child -- a pregnant woman can transmit the virus to her fetus through their shared blood circulation, or a nursing mother can pass it to her baby in her breast milk

People who become infected with HIV may have no symptoms for up to 10 years, but they can still pass the infection to others. After being exposed to the virus, it usually takes about 3 months for the HIV ELISA blood test to change from HIV negative to HIV positive.

HIV has spread throughout the U.S. The disease is more common in urban areas, especially in inner cities.

See also: AIDS for a more complete description of how AIDS is spread.

Symptoms related to HIV are usually due to an infection in part of the body. Some symptoms related to HIV infection include:

• Diarrhea
• Fatigue
• Fever
• Frequent vaginal yeast infections
• Headache
• Mouth sores, including yeast infection (thrush)
• Muscle stiffness or aching
• Rash of different types, including seborrheic dermatitis
• Sore throat
• Swollen lymph glands

Note: When they are diagnosed with HIV infection, many people have not had any symptoms.

The HIV ELISA and HIV Western blot tests detect antibodies to the HIV virus in the blood. Both tests must be positive to confirm an HIV infection. Having these antibodies means you are infected with HIV.

• If the test is negative (no antibodies found) and you have risk factors for HIV infection, you should be retested in 3 months.
• If the HIV ELISA and HIV Western blot tests are positive, other blood tests can be done to determine how much HIV is in your bloodstream.

A complete blood count (CBC) and white blood cell differential may also show abnormalities.

A lower-than-normal CD4 cell count may be a sign that the virus is damaging your immune system.

Doctors often recommend drug therapy for patients who are committed to taking all their medications and have a CD4 count below 500 cells/mm³ (indicating their immune system is suppressed). Some people, including pregnant women and people with kidney or neurological problems related to HIV, may need treatment regardless of their CD4 count.

It is extremely important for people with HIV to take all doses of their medications, otherwise the virus may become resistant to the drugs. Therapy always involves a combination of antiviral drugs. Pregnant women with HIV infection are treated to reduce the chance of transmitting HIV to their babies.

People with HIV infection need to become educated about the disease and treatment so that they can be active participants in making decisions with their health care provider.

See: AIDS - support group

HIV is a chronic medical condition that can be treated, but not yet cured. There are effective ways to prevent complications and delay, but not always prevent, progression to AIDS.

Almost all people infected with HIV will develop AIDS if not treated. However, there is a small group of people who develop AIDS very slowly, or never at all. These patients are called long-term nonprogressors.

• Cancers
• Chronic wasting (weight loss) from HIV infection
• HIV dementia
• HIV lipodystrophy
• Opportunistic infections
  • Bacillary angiomatosis
  • Candidiasis
  • Cytomegalovirus infection
  • Cryptococcal infection
  • Cryptosporidium enterocolitis (or other protozoal infections)
  • Mycobacterium avium complex (MAC) infection
  • Pneumocystis jiroveci pneumonia (previously called Pneumocystis carinii pneumonia or PCP)
  • Salmonella infection in the bloodstream
  • Toxoplasmosis
  • Tuberculosis (in the lungs or spread throughout the body)
  • Viral infection of the brain (progressive multifocal leukoencephalopathy)

Call your health care provider if you have had a possible or actual exposure to AIDS or HIV infection.

• Avoid injected illicit drugs. If you use injected drugs, avoid sharing needles or syringes. Always use new needles. (Boiling or cleaning them with alcohol does not guarantee that they're sterile and safe.)
• Avoid oral, vaginal, or anal contact with semen from HIV-infected people.
• Avoid unprotected anal intercourse, since it causes small tears in the rectal tissues, through which HIV in an infected partner's semen may enter directly into the other partner's blood.
• If you have sex with people who use injected drugs, always use protection.
• If you have sex with many people or with people who have multiple partners, always use protection.
• People with AIDS or who have had positive HIV antibody tests can pass the disease on to others. They should not donate blood, plasma, body organs, or sperm. They should not exchange genital fluids during sexual activity.
• Safer sex behaviors may reduce the risk of getting the infection. There is still a slight risk of getting the infection even if you practice "safe sex" by using condoms. Abstinence is the only sure way to prevent sexual transmission of the virus.
• Use protection when having sexual contact with people you know or suspect of being infected with HIV. Even better, use protection for ALL sexual contact.

Piot P. Human immunodeficiency virus infection and acquired immunodeficiency syndrome: A global overview. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier;2007:chap 407.

Del Rio C, Curran JW. Epidemiology and prevention of acquired immunodeficiency syndrome and human immunodeficiency virus infection. In: Mandell GL, Bennett JE, Dolin R, eds. Principles and Practice of Infectious Diseases. 7th ed. Philadelphia, Pa: Elsevier Churchill Livingstone; 2009:chap 118.

Sterling TR, Chaisson RE. General clinical manifestations of human immunodeficiency virus infection (including the acute retroviral syndrome and oral, cutaenous, renal, ocular, metabolic, and cardiac diseases. In: Mandell GL, Bennett JE, Dolin R, eds. Principles and Practice of Infectious Diseases. 7th ed. Philadelphia, Pa: Elsevier Churchill Livingstone; 2009:chap 121.