HIV is a retrovirus that infects cells of the immune system, destroying or impairing their function. As the infection progresses, the immune system becomes weaker, and the person becomes more susceptible to infections.
- HIV continues to be a major global public health issue, having claimed more than 25 million lives over the past three decades.
- There were approximately 34 [31.4–35.9] million people living with HIV in 2011.
- Sub-Saharan Africa is the most affected region, with nearly 1 in every 20 adults living with HIV. Sixty nine per cent of all people living with HIV are living in this region.
- HIV infection is usually diagnosed through blood tests detecting the presence or absence of HIV antibodies.
- There is no cure for HIV infection. However, effective treatment with antiretroviral drugs can control the virus so that people with HIV can enjoy healthy and productive lives.
- In 2011, more than 8 million people living with HIV were receiving antiretroviral therapy (ART) in low- and middle-income countries. Another 7 million people need to be enrolled in treatment to meet the target of providing ART to 15 million people by 2015.
The Human Immunodeficiency Virus (HIV) targets the immune system and weakens people's surveillance and defense systems against infections and some types of cancer. 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. Immunodeficiency results in increased susceptibility to a wide range of infections and diseases that people with healthy immune systems can fight off. The most advanced stage of HIV infection is Acquired Immunodeficiency Syndrome (AIDS), which can take from 2 to 15 years to develop depending on the individual. AIDS is defined by the development of certain cancers, infections, or other severe 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, many are unaware of their status until later stages. The first few weeks after initial infection, individuals may experience no symptoms or an influenza-like illness including fever, headache, rash or sore throat.
As the infection progressively weakens the person's immune system, the individual 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, cryptococcal meningitis, and cancers such as lymphomas and Kaposi's sarcoma, among others.
HIV can be transmitted via the exchange of a variety of body fluids from infected individuals, such as blood, breast milk, semen and vaginal secretions. Individuals cannot become infected through ordinary day-to-day contact such as kissing, hugging, shaking hands, or sharing personal objects, food or water.
Behaviours and conditions that put individuals at greater risk of contracting HIV include:
- having unprotected anal or vaginal sex;
- having another sexually transmitted infection 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, medical procedures that involve unsterile cutting or piercing; and
- experiencing accidental needle stick injuries, including among health workers.
An HIV test reveals infection status by detecting the presence or absence of antibodies to HIV in the blood. Antibodies are produced by an individual’s immune system to fight off foreign pathogens. Most people have a "window period" of usually 3 to 6 weeks during which antibodies to HIV are still being produced and are not yet detectable. This early period of infection represents the time of greatest infectivity, but transmission can occur during all stages of the infection. If someone has had a recent possible HIV exposure, retesting should be done after 6 weeks to confirm test results, which enables sufficient time to pass for antibody production in infected individuals.
Testing and counselling
HIV testing should be voluntary and the right to decline testing should be recognized. Mandatory or coerced testing by a health-care provider, authority or from a partner or family member is not acceptable as it undermines good public health practice and infringes on human rights.
All testing and counselling services must include the five C’s recommended by WHO: informed Consent, Confidentiality, Counselling, Correct test results and linkage to Care, treatment and other services.
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:
1. Male and female condom use
Correct and consistent use of male and female condoms during vaginal or anal penetration can protect against the spread of sexually transmitted infections, including HIV. Evidence shows that male latex condoms have an 85% or greater protective effect against the sexual transmission of HIV and other sexually transmitted infections (STIs).
2. Testing and counselling for HIV and STIs
Testing for HIV and other STIs is strongly advised for all people exposed to any of the risk factors so that they can learn of their own infection status and access necessary prevention and treatment services without delay. WHO also recommends offering testing for partners or couples.
3. Voluntary medical male circumcision
Medical male circumcision, when safely provided by well-trained health professionals, reduces the risk of heterosexually acquired HIV infection in men by approximately 60%. This is a key intervention in generalized epidemic settings with high HIV prevalence and low male circumcision rates.
4. ARV based prevention
4.1 ART as prevention
A recent trial has confirmed if an HIV-positive person adheres to an effective antiretroviral therapy regimen, the risk of transmitting the virus to their uninfected sexual partner can be reduced by 96%. For couples in which one partner is HIV-positive and the other HIV-negative, WHO recommends offering ART for the HIV-positive partner regardless of her/his CD4 count.
4.2 Pre-exposure prophylaxis (PrEP) for HIV-negative partner
Trials among serodiscordant couples have demonstrated that antiretroviral drugs taken by the HIV-negative partner can be effective in preventing HIV acquisition from the HIV-positive partner. This is known as pre-exposure prophylaxis (PrEP).
4.3 Post-exposure prophylaxis for HIV (PEP)
Post-exposure prophylaxis (PEP) is the use of ARV drugs within 72 hours of exposure to HIV in order to prevent infection. PEP is often recommended for health-care workers following needle stick injuries in the workplace. PEP includes counselling, first aid care, HIV testing, and depending on risk level, administering of a 28-day course of antiretroviral drugs with follow-up care.
5. Harm reduction for injecting drug users
People who inject drugs can take precautions against becoming infected with HIV by using sterile injecting equipment, including needles and syringes, for each injection. A comprehensive package of interventions for HIV prevention and treatment includes:
- needle and syringe programmes;
- opioid substitution therapy for people dependent on opioids and other evidence based drug dependence treatment;
- HIV testing and counselling;
- HIV treatment and care;
- access to condoms; and
- management of STIs, tuberculosis and viral hepatitis.
6. Elimination of mother-to-child transmission of HIV (eMTCT)
The transmission of HIV from an HIV-positive mother to her child during pregnancy, labour, delivery or breastfeeding is called vertical or mother-to-child transmission (MTCT). In the absence of any interventions HIV transmission rates are between 15-45%. MTCT can be nearly fully prevented if both the mother and the child are provided with antiretroviral drugs throughout the stages when infection could occur.
WHO recommends a range of options for prevention of MTCT (PMTCT), which includes providing ARVs to mothers and infants during pregnancy, labour and the post-natal period, or offering life-long treatment to HIV-positive pregnant women regardless of their CD4 count. New guidelines for PMTCT will be issued in 2013.
In 2011, 57% of the estimated 1.5 million pregnant women living with HIV in low- and middle-income countries received effective antiretroviral drugs to avoid transmission to their children, up from 48% in 2010.
HIV can be suppressed by combination antiretroviral therapy (ART) consisting of three or more antiretroviral (ARV) drugs. ART does not cure HIV infection but controls viral replication within a person's body and allows an individual's immune system to strengthen and regain the capacity to fight off infections. With ART, people living with HIV can live healthy and productive lives.
More than 8 million people living with HIV in low- and middle-income countries were receiving ART at the end of 2011. Of this, about 562 000 were children. This is a 20-fold increase in the number of people receiving ART in developing countries between 2003 and 2011, and a 20% increase in just one year (from 6.6 million in 2010 to more than 8 million in 2011).
By the end of 2011, 54% of the people eligible for treatment were receiving ART. Coverage is highest in Latin America (70%) and the Caribbean (67%), followed by sub-Saharan Africa (56%), Asia (44%), Eastern Europe and Central Asia (23%) and lowest in the Middle-East and North Africa (13%).