HIV/AIDS

The Human Immunodeficiency Virus (HIV) targets the immune system and weakens people's 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, cancers and other 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.

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 immune system, an individual can develop other signs and symptoms, such as swollen lymph nodes, weight loss, fever, diarrhea and cough. Without treatment, they could also develop severe illnesses such as tuberculosis, cryptococcal meningitis, severe bacterial infections 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.

Behaviors 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, gonorrhea, and bacterial vaginosis;
• sharing contaminated needles, syringes and other injecting equipment and drug solutions when injecting drugs;
• receiving unsafe injections, blood transfusions, tissue transplantation, medical procedures that involve unsterile cutting or piercing; and
• experiencing accidental needle stick injuries, including among health workers.

Serological tests, such as rapid diagnostic tests (RDTs) or enzyme immunoassays (EIAs), detect the presence or absence of antibodies to HIV-1/2 and/or HIV p24 antigen. No single HIV test can provide an HIV-positive diagnosis. It is important that these tests are used in combination and in a specific order that has been validated and is based on HIV prevalence of the population being tested. HIV infection can be detected with great accuracy, using WHO prequalified tests within a validated approach.

It is important to note that serological tests detect antibodies produced by an individual as part of their immune system to fight off foreign pathogens, rather than direct detection of HIV itself. Most individuals develop antibodies to HIV within 21 days of infection, during the so-called window period. This early period of infection represents the time of greatest infectivity; however, HIV transmission can occur during all stages of the infection. No currently available serological or virological assay can detect any marker of HIV with less than 10 days of infection.

It is best practice to also retest all people initially diagnosed as HIV-positive before they enroll in care and/or treatment 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.

Testing and diagnosis of HIV-exposed infants has been a challenge. For infants and children less than 18 months of age, serological testing is not sufficient to identify HIV infection – virological testing must be provided (at 6 weeks of age, or as early as birth) to detect the presence of the virus in infants born to mothers living with HIV.

However, new technologies are now available to perform the test at the point of care and enable return of the result on the same day to accelerate appropriate linkage and treatment initiation.

Individuals can reduce the risk of HIV infection by limiting exposure to risk factors. However, besides reducing risk-taking behaviors, the prevention of HIV and other STIs also depend on the level of vulnerability of individual and communities.

In the context of HIV/AIDS, prevention is a result the interaction of: 
(i) personal aspects;
(ii) the quality and coverage of health services, including those aimed at prevention, care, social support and impact-alleviation; and
(iii) interpersonal, societal and environmental factors, including gender and social inequities across different contexts and cultures.

See Combination HIV Prevention.

Antiretroviral therapy (ART) is treatment of people infected with human immunodeficiency virus (HIV) using anti-HIV drugs. The standard treatment consists of a combination of drugs (often called "highly active antiretroviral therapy" or HAART) that suppress HIV replication. The combination of drugs is used in order to increase potency and reduce the likelihood of the virus developing resistance. ART reduces mortality and morbidity rates among HIV-infected people, and improves their quality of life. The benefits of ART also include the prevention of HIV transmission by suppressing HIV replication in persons living with the virus. This benefit of ART is also defined as “undetectable equal untransmittable” , or U=U.