The Human Immunodeficiency Virus (HIV) targets the immune system and weakens people's surveillance and defence systems against infections and some types of cancer. As the virus destroys and impairs the function of immune cells, infected individuals gradually become immunodeficient. 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 10-15 years to develop. This stage is defined by the development of certain cancers, infections, or other severe clinical manifestations.
HIV is one of the world's leading infectious killers, claiming more than 25 million lives over the last 30 years. In 2010, there were approximately 34 million people living with HIV. Over 60% of people living with HIV are in sub-Saharan Africa.
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 a flu-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 unprotected and close contact with a variety of body fluids of 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.
Examples of HIV transmission routes include:
There are certain behaviours that put individuals at a greater risk for contracting HIV. These include:
An HIV test reveals infection status by detecting the presence or absence of antibodies to HIV in the blood. Antibodies are produced by individuals' immune systems to fight off foreign pathogens. Most people have a "window period" of 3 to 12 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. Retesting should be done after three months to confirm test results once sufficient time has passed for antibody production in infected individuals.
People must agree to be tested for HIV and appropriate counselling should be provided. HIV test results should be kept confidential, and everyone should receive post-test counselling and follow-up care, treatment and prevention measures as appropriate.
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 power to fight off infections. With ART, HIV-infected individuals can live healthy and productive lives.
An estimated 6.6 million people living with HIV in low- and middle-income countries were receiving ART at the end of 2010. Of this, an estimated 420 000–460 000 were children. This is a 16-fold increase in the number of people receiving ART in developing countries between 2003 and 2010.
Individuals can reduce the risk of HIV infection by limiting exposure to risk factors. Key approaches for HIV prevention include:
1. 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.
3. Pre-exposure prophylaxis (PrEP) for HIV-negative partner
Two trials have demonstrated that a daily dose of antiretroviral drugs tenofovir and tenofovir/emtricitabine taken by an HIV-negative partner is effective in preventing acquisition from an HIV-positive partner. These results are being further investigated by WHO.
4. Post-exposure prophylaxis for HIV (PEP)
This method includes immediate use of ARV drugs within the first 72 hours following accidental exposure to HIV in order to prevent infection. PEP is often recommended for health care workers exposed to needle stick injuries in the workplace. PEP also 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. Male circumcision
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 epidemics with high HIV prevalence and low male circumcision rates.
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. In the absence of any interventions transmission rates are between 15-45%. MTCT can be fully prevented if both the mother and the child are provided with ART or antiretroviral drug prophylaxis throughout the stages when infection could occur.
A new 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%. WHO is recommending ART as a key part of HIV prevention strategies.
8. 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 HIV prevention and treatment, particularly opioid substitution therapy for drug users includes drug dependence treatment HIV testing and counselling, HIV treatment and care, and access to condoms and management of STIs, tuberculosis and viral hepatitis.
(Source: WHO Fact sheet N°360)