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HIV (human immunodeficiency virus) is a virus that attacks the immune system, the body's natural defence system. Without a strong immune system, the body has trouble fighting off disease. Both the virus and the infection it causes are called HIV.
White blood cells are an important part of the immune system. HIV infects and destroys certain white blood cells called CD4+ cells. If too many CD4+ cells are destroyed, the body can no longer defend itself against infection.
The last stage of HIV infection is AIDS (acquired immunodeficiency syndrome). People with AIDS have a low number of CD4+ cells and get infections or cancers that rarely occur in healthy people. These can be deadly.
But having HIV doesn't mean you have AIDS. Even without treatment, it takes a long time for HIV to progress to AIDS—usually 10 to 12 years.
When HIV is diagnosed before it becomes AIDS, medicines can slow or stop the damage to the immune system. If AIDS does develop, medicines can often help the immune system return to a healthier state.
With treatment, many people with HIV are able to live long and active lives.
There are two types of HIV:
HIV infection is caused by the human immunodeficiency virus. You can get HIV from contact with infected blood, semen, or vaginal fluids.
HIV doesn't survive well outside the body. So it can't be spread by casual contact like kissing or sharing drinking glasses with an infected person.
HIV may not cause symptoms early on. People who do have symptoms may mistake them for the flu or mono. Common early symptoms include:
Symptoms may appear from a few days to several weeks after a person is first infected. The early symptoms usually go away within 2 to 3 weeks.
After the early symptoms go away, an infected person may not have symptoms again for many years. After a certain point, symptoms reappear and then remain. These symptoms usually include:
A doctor may suspect HIV if symptoms last and no other cause can be found.
If you have been exposed to HIV, your immune system will make antibodies to try to destroy the virus. Doctors use tests to find these HIV antibodies or antigens in urine, saliva, or blood.
If a test on urine or saliva shows that you are infected with HIV, you will probably have a blood test to confirm the results.
Most doctors use a blood test to diagnose HIV infection. If the test is positive (meaning that HIV antibodies or antigens are found), a test to detect HIV DNA or RNA will be done to be sure.
HIV antibodies or antigens usually show up in the blood within 3 months. If you think you have been exposed to HIV but you test negative for it:
You can get HIV testing in most doctors' offices, public health units, hospitals, and HIV care clinics.
The standard treatment for HIV is a combination of medicines called antiretroviral therapy, or ART. Antiretroviral medicines slow the rate at which the virus multiplies.
Taking these medicines can reduce the amount of virus in your body and help you stay healthy.
To monitor the HIV infection and its effect on your immune system, a doctor will regularly do two tests:
After you start treatment, it's important to take your medicines exactly as directed by your doctor. When treatment doesn't work, it is often because HIV has become resistant to the medicine. This can happen if you don't take your medicines correctly.
HIV is often spread by people who don't know they have it. So it's always important to protect yourself and others by taking these steps:
If you are at high risk for getting infected with HIV, you can take antiretroviral medicine to help protect yourself from HIV infection. Experts may recommend this for:footnote 1, footnote 2
To keep your risk low, you still need to practice safer sex even while you are taking the medicine.
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The HIV infection is caused by the human immunodeficiency virus (HIV).
After HIV is in the body, it starts to destroy CD4+ cells, which are white blood cells that help the body fight infection and disease.
HIV is spread when blood, semen, or vaginal fluids from an infected person enter another person's body, usually through sexual contact, from sharing needles when injecting drugs, or from mother to baby during birth.
HIV may not cause symptoms early on. People who do have symptoms may mistake them for influenza (flu) or mono. Early symptoms of HIV are called acute retroviral syndrome. The symptoms may include:
These first symptoms can range from mild to severe and usually disappear on their own after 2 to 3 weeks. But many people don't have symptoms or they have such mild symptoms that they don't notice them at this stage.
After the early symptoms go away, an infected person may not have symptoms again for many years. After a certain point, symptoms reappear and then remain.
Untreated HIV infection progresses in stages. These stages are based on your symptoms and the amount of the virus in your blood.
Later symptoms may include:
HIV is spread when blood, semen, or vaginal fluids from an infected person enter another person's body, usually through:
HIV may be spread more easily in the early stage of infection and again later, when symptoms of HIV-related illness develop.
A woman who is infected with HIV can spread the virus to her baby during pregnancy, delivery, or breastfeeding.
The virus doesn't survive well outside the body. So HIV cannot be spread through casual contact with an infected person, such as by sharing drinking glasses, by casual kissing, or by coming into contact with the person's sweat or urine.
It is now extremely rare in Canada or the United States for HIV to be transmitted by blood transfusions or organ transplants.
After you've been infected, it can take 2 weeks to 3 months for your body to start making HIV antibodies.
This means that during this time you could have a negative HIV test, even though you have been infected and can spread the virus to others.
This is commonly called the "window period," or seroconversion period.
If the HIV infection is not treated, people go through the following stages:
The first stage of HIV infection is defined as a CD4+ cell count of at least 500 cells per microlitre or a percentage of CD4+ cells at least 29% of all lymphocytes. People in this stage don't have any symptoms.footnote 5
The second stage of HIV infection is defined by the CDC as a CD4+ cell count of 200 to 499 or a percentage of CD4+ cells of 14% to 28%.footnote 5 It may take years for HIV symptoms to develop during this stage. But even though no symptoms are present, the virus is making copies of itself (multiplying) in the body during this time.
HIV multiplies so quickly that the immune system can't destroy the virus. After years of fighting HIV, the immune system starts to weaken.
AIDS occurs when the CD4+ cell counts drop below 200, the percentage of CD4+ cells is less than 14%, or an AIDS-defining condition is present.footnote 6
If HIV isn't treated, most people get AIDS within 10 to 12 years after the initial infection. With treatment for HIV, the progression to AIDS may be delayed or prevented.
After your immune system starts to weaken, you are more likely to get certain infections or illnesses, called opportunistic infections. Examples include some types of pneumonia or cancer that are more common when you have a weakened immune system.
A small number of people who are infected with HIV are rapid progressors. They develop AIDS within a few years if they don't get treatment. It is not known why the infection progresses faster in these people.
Left untreated, AIDS is often fatal within 18 to 24 months after it develops. Death may occur sooner in people who rapidly progress through the stages of HIV or in young children.
A few people have HIV that doesn't progress to more severe symptoms or disease. They are referred to as non-progressors.
A small number of people never become infected with HIV despite years of exposure to the virus. These people are said to be HIV-resistant.
You have an increased risk of becoming infected with HIV through sexual contact if you:
People who inject drugs or steroids, especially if they share needles, syringes, cookers, or other equipment used to inject drugs, are at risk of being infected with HIV.
Babies who are born to mothers who are infected with HIV are also at risk of infection.
Most children younger than 13 years who have HIV were infected with the virus by their mothers.
If you are infected with HIV or caring for someone who is, call 911 or other emergency services immediately if any of the following conditions develop:
Call your doctor if any of the following conditions develop:
Call your doctor to find out whether HIV testing is needed if you suspect you have been exposed to HIV, particularly if you engage in high-risk behaviour and have any of the following symptoms:
If you have not been tested for HIV, call your doctor if:
Getting tested for HIV can be scary, but the condition can be managed with treatment. So it is important to get tested if you think you have been exposed.
Your family doctor or general practitioner can diagnose and may treat HIV. You may be referred to a specialist, such as an internist, infectious disease specialist, or medical microbiologist.
HIV can also be diagnosed and treated at an HIV care clinic.
Complications of HIV may require treatment by the following doctors:
Public health units and other organizations may provide free or low-cost, confidential testing and counselling about HIV and high-risk behaviour.
If you don't have a doctor, contact one of the following for information on HIV testing in your area:
The Public Health Agency of Canada recommends HIV testing for:footnote 7
HIV testing may also be recommended for:
You and your doctor can decide if testing is right for you.
Some people are afraid to be tested for HIV. But if there is any chance you could be infected, it is very important to find out. HIV can be treated. Getting early treatment can slow down the virus and help you stay healthy. And you need to know if you are infected so you can prevent spreading the infection to other people.
Your doctor may recommend counselling before and after HIV testing. It is usually available at the hospital or clinic where you will be tested. This will give you an opportunity to:
Testing positive for HIV will probably make you anxious and afraid about your future. Denial, fear, and depression are common reactions.
Don't be afraid to ask for the emotional support you need. If your family and friends aren't able to provide you with support, a professional counsellor can help.
The good news is that people being treated for HIV are living longer than ever before with the help of medicines that can often prevent AIDS from developing. Your doctor can help you understand your condition and how best to treat it.
HIV is diagnosed when HIV antibodies or antigens are found in the blood.
A diagnosis of HIV infection is not made until a positive ELISA test is confirmed by a positive test to detect HIV DNA or RNA, such as a PCR test.
Until you know the results of your test:
If you test positive, your doctor will complete a medical history and physical examination.
He or she may order several lab tests to check your overall health, including:
Other tests may be done to check for current or past infections that may become worse because of HIV. You may be tested for:
When you have HIV, two tests are done regularly to see how much of the virus is in your blood (viral load) and how the virus is affecting your immune system:
The results of these tests may help you make decisions about starting treatment or switching to new medicines if the ones you are taking aren't helping.
HIV often changes or mutates in the body. Sometimes these changes make the virus resistant to certain medicines. Then the medicine no longer works.
Medical experts recommend testing the blood of everyone diagnosed with HIV to look for this drug resistance.footnote 8 This information helps your doctor know what medicines to use.
You also may be tested for drug resistance when:
AIDS is the last and most severe stage of HIV infection. It is diagnosed if the results of your test show that you have a certain kind of infection called an opportunistic infection that is common in people who have weakened immune systems, such as Kaposi's sarcoma or Pneumocystispneumonia.
The most effective treatment for HIV is antiretroviral therapy (ART), a combination of several medicines that aims to control the amount of virus in your body. For more information, see Medications.
Other steps you can take include the following:
Medical experts recommend that people begin treatment for HIV as soon as they know that they are infected.footnote 9, footnote 10 Treatment is especially important for pregnant women, people who have other infections (such as tuberculosis or hepatitis), and people who have symptoms of AIDS.
Research suggests that treatment of early HIV with antiretroviral medicines has long-term benefits, such as a stronger immune system, delay in onset of AIDS, and longer life expectancy.footnote 9, footnote 11
If you put off treatment, you will still need regular checkups to measure the amount of HIV in your blood and your CD4 cell count to see how well your immune system is working.
You may want to start HIV treatment if your sex partner doesn't have HIV. Treatment of your HIV infection can help prevent the spread of HIV to your sex partner.footnote 12
Learning how to live with HIV infection may keep your immune system strong, while also preventing the spread of HIV to others.
If your partner has HIV:
If HIV progresses to a late stage, treatment will be started or continued to keep your immune system as healthy as possible.
If you get any diseases that point to AIDS, such as Pneumocystis pneumonia or Kaposi's sarcoma, your doctor will treat them.
Many important end-of-life decisions can be made while you are active and able to communicate your wishes. For more information, see the topic Care at the End of Life.
Health care workers who are at risk for HIV because of an accidental needle stick or other exposure to body fluids may need medicine to prevent infection.footnote 13
Medicine may also prevent HIV infection in a person who has been raped or was accidentally exposed to the body fluids of a person who may have HIV.footnote 14 This type of treatment is usually started within 72 hours of the exposure.
Studies have shown that treatment with antiretroviral medicine also can reduce the risk of an uninfected person getting infected through sex.footnote 15, footnote 16
Practice safer sex. This includes using a condom unless you are in a relationship with one partner who does not have HIV or other sex partners.
If you do have sex with someone who has HIV, it is important to practice safer sex and to be regularly tested for HIV.
Talk with your sex partner or partners about their sexual history as well as your own sexual history. Find out whether your partner has a history of behaviours that increase his or her risk for HIV.
You may be able to take a combination medicine (tenofovir plus emtricitabine) every day to help prevent infection with HIV. This medicine can lower the risk of getting HIV.footnote 18, footnote 19, footnote 20 But the medicine is expensive, and you still need to practice safer sex to keep your risk low.
If you use alcohol or drugs, be very careful. Being under the influence can make you careless about practicing safer sex.
And never share intravenous (IV) needles, syringes, cookers, cotton, cocaine spoons, or eyedroppers with others if you use drugs.
If you are infected with HIV, you can greatly lower the risk of spreading the infection to your sex partner by starting treatment when your immune system is still healthy.
Experts recommend starting treatment as soon as you know you are infected.footnote 21
Studies have shown that early treatment greatly lowers the risk of spreading HIV to an uninfected partner.footnote 22, footnote 23
Your partner may also be able to take medicine to prevent getting infected.footnote 17 This is called pre-exposure prophylaxis (PrEP).
Steps to avoid spreading HIV
The risk of a woman spreading HIV to her baby can be greatly reduced if she:
The baby should also receive treatment after it is born.
If you are infected with HIV, you can lead an active life for a long time.
Support groups are often good places to share information, problem-solving tips, and emotions related to HIV infection.
You may be able to find a support group by searching the Internet. Or you can ask your doctor to help you find one.
Get the immunizations and the medicine treatment you need to prevent certain infections or illnesses, such as some types of pneumonia or cancer that are more likely to develop in people who have a weakened immune system.
A skilled caregiver can provide the emotional, physical, and medical care that will improve the quality of life for a person who has HIV.
Medicines used to treat HIV are called antiretrovirals. Several of these are combined for treatment called antiretroviral therapy, or ART.
When choosing medicines, your doctor will think about:
Medicines for HIV may have unpleasant side effects. They may sometimes make you feel worse than you did before you started taking them. Talk to your doctor about your side effects. He or she may be able to adjust your medicines or prescribe a different one.
You may be able to take several medicines combined into one pill. This reduces the number of pills you have to take each day.
Resistance to HIV medicines can occur when:
Using antiretroviral therapy (ART) reduces your risk of developing resistance to HIV medicines.
If your viral load doesn't drop as expected, or if your CD4+ cell count starts to fall, your doctor will try to find out why the treatment didn't work.
There are two main reasons that treatment fails:
Counselling may help you to:
Reducing stress can help you better manage the HIV illness. Some methods of stress reduction include:
Cannabis has been shown to stimulate the appetite and relieve nausea. Talk to your doctor if you're interested in trying it.
Alternative and complementary treatments for HIV need to be carefully evaluated.
Some people with HIV may use these types of treatment to help with fatigue and weight loss caused by HIV infection and reduce the side effects caused by antiretroviral therapy (ART).
Some complementary therapies for other problems may actually be harmful. For example, St. John's wort decreases the effectiveness of certain prescription medicines for HIV.
Make sure to discuss complementary therapies with your doctor before trying them.
CitationsU.S. Centers for Disease Control and Prevention (2017). Preexposure prophylaxis for the prevention of HIV infection in the United States—2017 update: A clinical practice guideline. U.S. Centers for Disease Control and Prevention. https://www.cdc.gov/hiv/pdf/risk/prep/cdc-hiv-prep-guidelines-2017.pdf. Accessed July 28, 2018.CATIE (2016). Pre-exposure prophylaxis (PrEP) resources. CATIE. http://www.catie.ca/en/prep. Accessed October 26, 2016. U.S. Department of Health and Human Services Panel on Antiretroviral Guidelines for Adults and Adolescents (2015). Guidelines for the use of antiretroviral agents in HIV-1-infected adults and adolescents. U.S. Department of Health and Human Services. http://aidsinfo.nih.gov/contentfiles/lvguidelines/adultandadolescentgl.pdf. Accessed May 5, 2015.Thompson MA, et al. (2012). Antiretroviral treatment of adult HIV infection: 2012 recommendations of the International Antiviral Society—USA Panel. JAMA, 308(4): 387–402.Schneider E, et al. (2008). Revised surveillance case definitions for HIV infection among adults, adolescents, and children aged < 18 months and for HIV infection and AIDS among children aged 18 months to < 13 years—United States, 2008. MMWR, 57(RR-10): 1–12. Also available online: http://www.cdc.gov/mmwr/PDF/rr/rr5710.pdf.U.S. Centers for Disease Control and Prevention (1992). 1993 Revised classification system for HIV infection and expanded surveillance case definition for AIDS among adolescents and adults. MMWR, 41(RR-17): 1–19.Public Health Agency of Canada (2012). Human immunodeficiency virus: HIV screening and testing guide. Available online: https://www.canada.ca/en/public-health/services/hiv-aids/hiv-screening-testing-guide.html#c1U.S. Department of Health and Human Services Panel on Antiretroviral Guidelines for Adults and Adolescents (2015). Guidelines for the use of antiretroviral agents in HIV-1-infected adults and adolescents. U.S. Department of Health and Human Services. http://aidsinfo.nih.gov/contentfiles/lvguidelines/adultandadolescentgl.pdf. Accessed May 5, 2015.U.S. Department of Health and Human Services Panel on Antiretroviral Guidelines for Adults and Adolescents (2015). Guidelines for the use of antiretroviral agents in HIV-1-infected adults and adolescents. U.S. Department of Health and Human Services. http://aidsinfo.nih.gov/contentfiles/lvguidelines/adultandadolescentgl.pdf. Accessed May 5, 2015.Thompson MA, et al. (2012). Antiretroviral treatment of adult HIV infection: 2012 recommendations of the International Antiviral Society—USA Panel. JAMA, 308(4): 387–402.CATIE (2016). Pre-exposure prophylaxis (PrEP) resources. CATIE. http://www.catie.ca/en/prep. Accessed October 26, 2016. U.S. Department of Health and Human Services Panel on Antiretroviral Guidelines for Adults and Adolescents (2013). Guidelines for the Use of Antiretroviral Agents in HIV-1-Infected Adults and Adolescents. Available online: http://www.aidsinfo.nih.gov/ContentFiles/AdultandAdolescentGL.pdf.Centers for Disease Control and Prevention (2005). Updated U.S. Public Health Services guidelines for the management of occupational exposures to HIV and recommendations for postexposure prophylaxis. MMWR, 50(RR-09): 1–17. Available online: http://www.cdc.gov/mmwr/preview/mmwrhtml/rr5409a1.htm.Centers for Disease Control and Prevention (2005). Antiretroviral postexposure prophylaxis after sexual, injection-drug use, or other nonoccupational exposure to HIV in the United States. Recommendations from the U.S. Department of Health and Human Services. Available online: http://www.cdc.gov/mmwr/preview/mmwrhtml/rr5402a1.htm.Grant RM, et al. (2010). Preexposure chemoprophylaxis for HIV prevention in men who have sex with men. New England Journal of Medicine, 363(27): 2588–2599.U.S. Centers for Disease Control and Prevention (2011). Interim guidance: Preexposure prophylaxis for the prevention of HIV infection in men who have sex with men. MMWR, 60(03): 65–68. Also available online: http://www.cdc.gov/mmwr/preview/mmwrhtml/mm6003a1.htm.U.S. Centers for Disease Control and Prevention (2017). Preexposure prophylaxis for the prevention of HIV infection in the United States—2017 update: A clinical practice guideline. U.S. Centers for Disease Control and Prevention. https://www.cdc.gov/hiv/pdf/risk/prep/cdc-hiv-prep-guidelines-2017.pdf. Accessed July 28, 2018.Grant RM, et al. (2010). Preexposure chemoprophylaxis for HIV prevention in men who have sex with men. New England Journal of Medicine, 363(27): 2588–2599.Baeten JM, et al. (2012). Antiretroviral prophylaxis for HIV prevention in heterosexual men and women. New England Journal of Medicine, 367(5): 399–410.Thigpen MC, et al. (2012). Antiretroviral preexposure prophylaxis for heterosexual HIV transmission in Botswana. New England Journal of Medicine, 367(5): 423–434.U.S. Department of Health and Human Services Panel on Antiretroviral Guidelines for Adults and Adolescents (2015). Guidelines for the use of antiretroviral agents in HIV-1-infected adults and adolescents. U.S. Department of Health and Human Services. http://aidsinfo.nih.gov/contentfiles/lvguidelines/adultandadolescentgl.pdf. Accessed May 5, 2015.Cohen MS, et al. (2011). Prevention of HIV-1 infection with early antiretroviral therapy. New England Journal of Medicine, July 18, epub ahead of print (doi:10.1056/NEJMoa1105243).Porco TC, et al. (2004). Decline in HIV infectivity following the introduction of highly active antiretroviral therapy. AIDS, 18(1): 81–88.Lazzaretti RK, et al. (2012). Dietary intervention prevents dyslipidemia associated with highly active antiretroviral therapy in human immunodeficiency virus type 1-infected individuals: A randomized trial. Journal of the American College of Cardiology, 59(11): 979–988.Triant VA, et al. (2007). Increased acute myocardial infarction rates and cardiovascular risk factors among patients with HIV disease. Journal of Clinical Endocrinology and Metabolism. Available online: http://jcem.endojournals.org/cgi/rapidpdf/jc.2006-2190v1 (e-pub ahead of print).Chaturvedi AK, et al. (2007). Elevated risk of lung cancer among people with AIDS. AIDS, 21(2): 207–213.Other Works ConsultedAmerican College of Obstetricians and Gynecologists (2008, reaffirmed 2011). Prenatal and perinatal human immunodeficiency virus testing: Expanded recommendations. ACOG Committee Opinion No. 418. Obstetrics and Gynecology, 112(3): 739–742.Eron JJ Jr, Hirsch MS (2008). Antiviral therapy of human immunodeficiency virus infection. In KK Holmes et al., eds., Sexually Transmitted Diseases, 4th ed., pp. 1393–1421. New York: McGraw-Hill.Gunthard HF, et al. (2016). Antiretroviral drugs for treatment and prevention of HIV infection in adults; 2016 Recommendations of the International Antiviral Society-USA Panel. JAMA, 316(2): 191–210. DOI: 10.1001/jama.2016.8900. Accessed August 2, 2016.Jia Z, et al. (2012). Antiretroviral therapy to prevent HIV transmission in serodiscordant couples in China (2003–11): A national observational cohort study. Lancet. Published online November 30, 2012 (doi:10.1016/S0140-6736(12)61898-4).Kitahata MM, et al. (2009). Effect of early versus deferred antiretroviral therapy for HIV on survival. New England Journal of Medicine. Published online April 1, 2009 (doi:10.1056/NEJMoa0807252).Panel on Opportunistic Infections in HIV-Exposed and HIV-Infected Children (2013). Guidelines for the prevention and treatment of opportunistic infections in HIV-exposed and HIV-infected children. Rockville, MD: Department of Health and Human Services. http://aidsinfo.nih.gov/contentfiles/lvguidelines/oi_guidelines_pediatrics.pdf. Accessed April 16, 2014.Rerks-Ngarm S, et al. (2009). Vaccination with ALVAC and AIDSVAX to prevent HIV-1 infection in Thailand. New England Journal of Medicine, 361(23): 2209–2220.U.S. Centers for Disease Control and Prevention (2009). Guidelines for prevention and treatment of opportunistic infections in HIV-infected adults and adolescents: Recommendations from CDC, the National Institutes of Health, and the HIV Medicine Association of the Infectious Diseases Society of America. MMWR, 58(Early Release): 1–207.World Health Organization (2010). Antiretroviral drugs for treating pregnant women and preventing HIV infection in infants: Recommendations for a public health approach, 2010 version. Available online: http://www.who.int/hiv/pub/mtct/antiretroviral2010/en/index.html.World Health Organization (2010). Antiretroviral therapy for HIV infection in adults and adolescents: Recommendations for a public health approach. Available online: http://whqlibdoc.who.int/publications/2010/9789241599764_eng.pdf.World Health Organization (2010). Antiretroviral therapy for HIV infection in infants and children: Towards universal access. Available online: http://whqlibdoc.who.int/publications/2010/9789241599801_eng.pdf.World Health Organization (2010). Guidelines on HIV and infant feeding 2010: Principles and recommendations for infant feeding in the context of HIV and a summary of evidence. Available online: http://whqlibdoc.who.int/publications/2010/9789241599535_eng.pdf.
Current as of: February 11, 2020
Author: Healthwise StaffMedical Review: E. Gregory Thompson MD - Internal MedicineAdam Husney MD - Family MedicinePeter Shalit MD, PhD - Internal Medicine
Current as of: February 11, 2020
Author: Healthwise Staff
Medical Review:E. Gregory Thompson MD - Internal Medicine & Adam Husney MD - Family Medicine & Peter Shalit MD, PhD - Internal Medicine
To learn more about Healthwise, visit Healthwise.org.
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