The human immunodeficiency virus (HIV) targets the immune system and weakens people's defense against many infections and some types of cancer that people with healthy immune systems can fight off. As the virus destroys and impairs the function of immune cells, infected individuals gradually become immunodeficient. Immune function is typically measured by CD4 cell count.
The most advanced stage of HIV infection is acquired immunodeficiency syndrome (AIDS), which can take many years to develop if not treated, depending on the individual. AIDS is defined by the development of certain cancers, infections or other severe long-term clinical manifestations.
Signs and symptoms
The symptoms of HIV vary depending on the stage of infection. Though people living with HIV tend to be most infectious in the first few months after being infected, many are unaware of their status until the later stages. In the first few weeks after initial infection people may experience no symptoms or an influenza- illness including fever, headache, rash or sore throat.
As the infection progressively weakens the immune system, they can develop other signs and symptoms, such as swollen lymph nodes, weight loss, fever, diarrhoea and cough. Without treatment, they could also develop severe illnesses such as tuberculosis (TB), cryptococcal meningitis, severe bacterial infections, and cancers such as lymphomas and Kaposi's sarcoma.
HIV can be transmitted via the exchange of a variety of body fluids from infected people, such as blood, breast milk, semen and vaginal secretions.
HIV can also be transmitted from a mother to her child during pregnancy and delivery.
Individuals cannot become infected through ordinary day-to-day contact such as kissing, hugging, shaking hands, or sharing personal objects, food or water.
It is important to note that people with HIV who are taking ART and are virally suppressed do not transmit HIV to their sexual partners. Early access to ART and support to remain on treatment is therefore critical not only to improve the health of people with HIV but also to prevent HIV transmission.
Behaviours and conditions that put individuals at greater risk of contracting HIV include:
- having unprotected anal or vaginal sex;
- having another sexually transmitted infection (STI) such as syphilis, herpes, chlamydia, gonorrhoea and bacterial vaginosis;
- sharing contaminated needles, syringes and other injecting equipment and drug solutions when injecting drugs;
- receiving unsafe injections, blood transfusions and tissue transplantation, and medical procedures that involve unsterile cutting or piercing; and
- experiencing accidental needle stick injuries, including among health workers
HIV can be diagnosed through rapid diagnostic tests that provide same-day results. This greatly facilitates early diagnosis and linkage with treatment and care. People can also use HIV self-tests to test themselves.
However, no single test can provide a full HIV diagnosis; confirmatory testing is required, conducted by a qualified and trained health or community worker at a community centre or clinic.
HIV infection can be detected with great accuracy using WHO prequalified tests within a nationally approved testing strategy.
Most widely-used HIV diagnostic tests detect antibodies produced by the person as part of their immune response to fight HIV. In most cases, people develop antibodies to HIV within 28 days of infection.
During this time, people experience the so-called “window” period – when HIV antibodies haven’t been produced in high enough levels to be detected by standard tests and when they may have had no signs of HIV infection, but also when they may transmit HIV to others.
After infection, an individual may transmit HIV transmission to a sexual or drug-sharing partner or for pregnant women to their infant during pregnancy or the breastfeeding period.
Following a positive diagnosis, people should be retested before they are enrolled in treatment and care to rule out any potential testing or reporting error. Notably, once a person diagnosed with HIV and has started treatment they should not be retested.
While testing for adolescents and adults has been made simple and efficient, this is not the case for babies born to HIV-positive mothers.
For children less than 18 months of age, serological testing is not sufficient to identify HIV infection – virological testing must be provided as early as birth or at 6 weeks of age.
New technologies are now becoming available to perform this test at the point of care and enable same-day results, which will accelerate appropriate linkage with treatment and care.
Individuals can reduce the risk of HIV infection by limiting exposure to risk factors. Key approaches for HIV prevention, which are often used in combination, include:
- male and female condom use;
- testing and counselling for HIV and STIs;
- testing and counselling for linkages to tuberculosis (TB) care;
- voluntary medical male circumcision (VMMC);
- use of antiretroviral drugs (ARVs) for prevention;
- harm reduction for people who inject and use drugs; and
- elimination of mother-to-child transmission of HIV.
HIV disease can be managed by treatment regimens composed of a combination of three or more antiretroviral (ARV) drugs.
Current antiretroviral therapy (ART) does not cure HIV infection but highly suppresses viral replication within a person's body and allows an individual's immune system recovery to strengthen and regain the capacity to fight off opportunistic infections and some cancers.
Since 2016, WHO has recommended that all people living with HIV be provided with lifelong ART, including children, adolescents, adults and pregnant and breastfeeding women, regardless of clinical status or CD4 cell count.
By June 2021, 187 countries had already adopted this recommendation, covering 99% of all people living with HIV globally.
In addition to the treat all strategy, WHO recommends a rapid ART initiation to all people living with HIV, including offering ART on the same day as diagnosis among those who are ready to start treatment.
By June 2021, 82 low- and middle-income countries reported that they have adopted this policy, and approximately half of them reported country-wide implementation.
Globally, 27.5million [26.5–27.7 million] people living with HIV were receiving ART in 2020. This equates to a global ART coverage rate of 73% [56–88%]. However, more efforts are needed to scale up treatment, particularly for children and adolescents. Only 54% [37–69%] of children (0–14 years old) were receiving ART at the end of 2020.
The Sixty-Ninth World Health Assembly endorsed the “Global health sector strategy on HIV for 2016–2021”. The strategy includes five strategic directions that guide priority actions by countries and by WHO over six years.
The strategic directions are:
- Information for focused action (know your epidemic and response)
- Interventions for impact (covering the range of services needed)
- Delivering for equity (covering the populations in need of services)
- Financing for sustainability (covering the costs of services)
- Innovation for acceleration (looking towards the future).
WHO is a cosponsor of the Joint United Nations Programme on AIDS (UNAIDS). Within UNAIDS, WHO leads activities on HIV treatment and care, and HIV and TB coinfection, and jointly coordinates the work on elimination of MTCT of HIV with UNICEF.
- Global health sector strategy on HIV, 2016-2021
- Consolidated HIV strategic information guidelines
Who Should Get Tested?
The only way to know for sure whether you have HIV is to get tested. CDC recommends that everyone between the ages of 13 and 64 get tested for HIV at least once as part of routine health care.
Knowing your HIV status gives you powerful information to help you take steps to keep you and your partner(s) healthy. About 1 in 8 people in the United States who have HIV do not know they have it.
Should You Get Tested for HIV?
Everyone between the ages of 13 and 64 should get tested for HIV at least once. If your behavior puts you at risk after you are tested, you should think about being tested again. Some people at higher risk should get tested more often.
If your last HIV test result was negative, you should get an HIV test if you answer «yes» to any of the questions below about your risk since that test:
- Are you a man who has had sex with another man?
- Have you had sex—anal or vaginal—with an HIV-positive partner?
- Have you had more than one sex partner?
- Have you injected drugs and shared needles or works (for example, water or cotton) with others?
- Have you exchanged sex for drugs or money?
- Have you been diagnosed with, or sought treatment for, another sexually transmitted disease?
- Have you been diagnosed with or treated for hepatitis or tuberculosis (TB)?
- Have you had sex with someone who could answer «yes» to any of the above questions or someone whose sexual history you don't know?
Sexually active gay and bisexual men may benefit from more frequent testing (for example, every 3 to 6 months).
If you're pregnant, talk to your health care provider about getting tested for HIV and other ways to protect you and your child from getting HIV.
Anyone who has been sexually assaulted or has had a high-risk exposure to HIV should consider taking post-exposure prophylaxis (PEP) and getting an HIV antigen test that can detect infection sooner than standard antibody testing. PEP may prevent HIV infection after possible exposure to HIV if it is started as soon as possible within 3 days after exposure to HIV.
How Can Testing Help You?
The only way to know for sure whether you have HIV is to get tested.
Knowing your HIV status gives you powerful information to help you take steps to keep you and your partner(s) healthy.
- If you test positive, you can take medicine to treat HIV . People with HIV who take HIV medicine as prescribed can live long and healthy lives. There’s also an important prevention benefit. If you take HIV medicine daily as prescribed and get and keep an undetectable viral load, you have effectively no risk of transmitting HIV to an HIV-negative partner through sex.
- If you test negative, you have more prevention tools available today to prevent HIV than ever before.
- If you are pregnant, you should be tested for HIV so that you can begin treatment if you're HIV-positive. If an HIV-positive woman is treated for HIV early in her pregnancy, the risk of transmitting HIV to her baby can be very low.
Is Self-Testing an Option?
Yes. HIV self-testing allows people to take an HIV test and find out their result in their own home or other private location. You can buy a self-test kit at a pharmacy or online, or your health care provider may be able to order one for you. Some health departments or community-based organizations also provide self-test kits for free.
Read the U.S. Food and Drug Administration’s (FDA) fact sheet on the OraQuick In-Home HIV Test, the only FDA-approved in-home HIV test.
The coronavirus (COVID-19) pandemic has made it more difficult for some people to access traditional places where HIV testing is provided. Self-testing allows people to get tested for HIV while still following stay-at-home orders and social distancing practices. Ask your local health department or HIV service organization if they offer self-testing kits.
Should You Get Tested for HIV If You Don’t Think You’re at High Risk?
Some people who test positive for HIV were not aware of their risk. That's why CDC recommends that everyone between the ages of 13 and 64 get tested for HIV at least once as part of routine health care and that people with certain risk factors should get tested more often (see above).
Even if you are in a monogamous relationship (both you and your partner are having sex only with each other), you should find out for sure whether you or your partner has HIV.
Should You Get Tested for HIV If You’re Pregnant?
All pregnant women should be tested for HIV so that they can begin treatment if they're HIV-positive.
If a woman is treated for HIV early in her pregnancy, the risk of transmitting HIV to her baby can be very low.
Testing pregnant women for HIV infection, treating those who are infected, and treating their babies with antiretroviral therapy (ART) after delivery have led to a big decline in the number of children born with HIV.
The treatment is most effective for preventing HIV transmission to babies when started as early as possible during pregnancy. If pregnant women are treated for HIV early in their pregnancy, the risk of transmitting HIV to their baby can be 1% or less. However, there are still great health benefits to beginning preventive treatment even during labor or shortly after the baby is born.
Learn more about how to protect yourself and your partners, and get information tailored to meet your needs from CDC's HIV Risk Reduction Tool (BETA).