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This article waslast modified on 18 February 2019.
What is HIV?

HIV (human immunodeficiency virus) is the virus that causes AIDS (acquired immunodeficiency syndrome). By killing or damaging cells of your body's immune system, HIV progressively destroys your body's ability to fight infections and certain cancers. People diagnosed with AIDS may get life-threatening diseases called opportunistic infections, which are caused by microbes such as viruses or bacteria that usually do not make healthy people sick.

How is HIV transmitted?

HIV is spread most commonly in these ways:

  • By having sex with an infected partner. The virus can enter the body through the lining of the vagina, vulva, penis, rectum, or mouth during sex.
  • Through contact with infected blood. Before blood was screened for evidence of HIV infection and before heat-treating techniques were introduced to destroy HIV in blood products, such as factor 8 and albumin, HIV was transmitted through transfusions of contaminated blood or blood components. Today, because of blood screening and heat treatment of blood derivatives, the risk of getting HIV from such transfusions is extremely small.
  • By sharing needles or syringes (such as during injection drug use), which can be contaminated with very small quantities of blood from someone infected with the virus. It is rare, however, for a patient to give HIV to a health care worker or vice-versa from contaminated needles or other medical instruments.
  • During pregnancy or birth. Approximately one-quarter to one-third of all untreated pregnant women infected with HIV will pass the infection to their babies. HIV also can be spread to babies through the breast milk of mothers infected with the virus. If the mother takes the drug AZT during pregnancy, she can significantly reduce the chances that her baby will be infected with HIV. If doctors treat mothers with AZT and deliver their babies by caesarean section, the chances of the baby being infected can be reduced to a rate of one percent.
  • Having a sexually transmitted disease such as syphilis, genital herpes, chlamydia, gonorrhoea, or bacterial vaginosis, which appears to make people more susceptible to and at higher risk for acquiring HIV infection during sex with infected partners.


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About HIV
  • Tests

    There are several types of tests associated with HIV disease. Some test for antibodies that the body makes in response to the virus, some test for the concentration of a protein (called p24) found in the virus, some test for the actual number of copies of the virus per milliliter of blood (called viral load testing), some test for levels of immune cells called CD4 cells that are attacked by HIV, and some test for whether patients are resistant to anti-HIV drugs.

    • Antibody testing—to diagnose HIV infection.
    • p24 protein testing—may be used to detect early HIV infection, to monitor HIV therapy and HIV progression, and to screen blood for HIV.
    • Viral load testing—to decide when to start therapy and to monitor therapy and HIV progression.
    • CD4 testing—to decide when to start therapy and to monitor therapy, HIV progression, and the status of the immune system.
    • Genotypic resistance testing—to determine if a particular strain of HIV is resistant to the therapy you are on and if the therapy should be switched.

    When are these tests requested?

    One or more of these tests are ordered after a person is exposed to HIV and decides to be tested, either at the doctor's surgery or a local clinic. Several of the tests listed above are then requested at intervals by a doctor to monitor the course of therapy.


  • Symptoms

    Many people do not develop any symptoms when they first become infected with HIV. Some people, however, have a flu-like illness within a month or two after exposure to the virus. This illness may include fever, headache, fatigue, and enlarged lymph nodes (organs of the immune system easily felt in the neck and groin). These symptoms usually disappear within a week to a month and are often mistaken for those of another viral infection. During this period, people are very infectious, and HIV is present in large quantities in genital fluids.

    More persistent or severe symptoms may not surface for a decade or more after HIV first enters the body in adults, or within two years in children born with HIV infection. This period of "asymptomatic" infection is highly individual. Some people may have symptoms in a few months, while others may be symptom-free for more than 10 years. During the asymptomatic period, however, the virus is actively multiplying, infecting, and killing immune system cells.

    The effect of HIV is most obvious in the decline in the blood levels of your CD4 T cells (also called T4 cells), the immune system's key infection fighters. At the beginning of its life in the human body, the virus disables or destroys these cells without causing symptoms.

    As the immune system deteriorates, a variety of complications occur. For many people, their first sign of infection is large lymph nodes or “swollen glands” that may be enlarged for more than three months. Other symptoms often experienced months to years before the onset of AIDS include:

    • lack of energy
    • weight loss
    • frequent fevers and sweats
    • persistent or frequent yeast infections (oral or vaginal)
    • persistent skin rashes or flaky skin
    • pelvic inflammatory disease (PID) in women that does not respond to treatment; or
    • short-term memory loss.

    Some people develop frequent and severe herpes infections that cause mouth, genital, or anal sores, or a painful nerve disease called shingles. Children may grow slowly or be sick a lot.


  • AIDS

    The term AIDS applies to the most advanced stages of HIV infection. The Centers for Disease Control (CDC) in Atlanta, GA, develops official criteria for the definition of AIDS. Their definition includes all HIV-infected people who have fewer than 200 CD4 T cells per cubic millimetre of blood. (Healthy adults usually have CD4 T-cell counts of 1,000 or more.) In addition, the definition includes 26 opportunistic infections that affect people who have advanced HIV disease. Most of these conditions are called opportunistic infections because they rarely cause medical problems in healthy people. In people with AIDS, these infections are often severe and sometimes fatal because the immune system is so damaged by HIV that the body cannot fight off certain bacteria, viruses, fungi, parasites, and other microbes.

    Opportunistic infections common in people with AIDS cause symptoms such as:

    • coughing and shortness of breath
    • seizures and lack of coordination
    • difficult or painful swallowing
    • mental symptoms such as confusion and forgetfulness
    • severe and persistent diarrhoea
    • fever
    • vision loss
    • feeling sick, abdominal cramps, and vomiting
    • weight loss and extreme fatigue;
    • severe headaches; and
    • coma


  • Common Questions

    1. How do I know whether I should get tested for HIV?

    Consider getting tested if:

    • you are sexually active,
    • you have shared needles for injecting drugs, or
    • you are an emergency worker who has come into contact with a hypodermic needle or a patient’s or victim’s blood.

    2. How confidential are HIV test results?

    Certain testing centres provide either anonymous (your name is never given) or confidential (your name is given but kept private) HIV testing and counselling.

    3. Should I tell anyone else of my results?

    Yes. If you test positive for HIV, it is important that you tell your health care providers as well as all current and future sex partners and/or anyone with whom you share needles. Counseling services are available that will help you to inform the people who need to know. For more information, visit the CDC’s Division of HIV/AIDS Prevention website for their HIV Counseling, Testing, and Referral Guidelines and Partner Counseling and Referral Services Guidance.

    4. Are there treatments for HIV/AIDS?

    Currently, there is no cure for HIV or AIDS. However, certain therapies can help. The CDC’s booklet, called Living with HIV/AIDS, is available online.

    5. Does everyone who has HIV get AIDS?

    Most people infected with HIV will develop AIDS. However, it may take several years. It is estimated that roughly 50% of people with HIV will develop AIDS within 10 years of becoming infected.

    6. Can you get HIV/AIDS from donating blood?

    No. It is very safe to donate blood because sterile needles are used.