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.

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 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.

Transmission

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.

Risk factors

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.

HIV Diagnosis

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.

Key facts

  • The number of new HIV cases in Latin America has had with only 1% reduction since 2010 with approximately 100 000 new persons infected each year. The Caribbean had a reduction of 18% from 2010 to 2017, down from an estimated 19 000 new cases to 15 000 per year. Approximately one third of new infections occur in young people (15-24 years old).
  • The HIV epidemic in the Region disproportionally affects certain sub-population (key populations), including gay men and other men who have sex with men (MSM) transgender women, and female sex workers. In Latin America, these three key populations account for approximately half of the new infections in 2017, and 37% in the Caribbean.
  • In 2017, an estimated 1.8 million people were living with HIV in Latin America, and 310 thousand in the Caribbean.
  • In Latin America, the number of people dying of AIDS-related death have decreased from its peak of 45 thousand in 2005 to 37 thousand in 2017, while the Caribbean had a reduction from 18 thousand to 10 thousand in the same period.
  • It is estimated that 23% of people with HIV in Latin America and 27% in the Caribbean are unaware of their infection, and approximately one third are diagnosed late, with advanced immunodeficiency (under 200 CD4 per mm3 of blood).
  • Approximately 1.1 million people living with HIV were receiving antiretroviral treatment (ART) in Latin America and 180 thousand in the Caribbean by the end of 2017, accounting for 61% ART coverage among all persons estimated to be living with HIV in Latin America and 57% in the Caribbean.

PAHO/WHO response

The 69th 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 the next 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).

In the Americas, countries have also endorsed the Plan of Action for the Prevention and Control of HIV and Sexually Transmitted Infections 2016-2021 to help accelerate the progress towards the end of AIDS and STI epidemics as public health problems by 2030 in the Region of the Americas. The goals of the regional Plan of Action are to reduce the incidence of new HIV infections, AIDS-related mortality, and STI-related complications. The Plan also integrates the goals of the previous Regional Strategy and Plan of Action for the Elimination of Mother-to-Child Transmission of HIV and Congenital Syphilis, reducing the rate of mother-to-child transmission of HIV and congenital syphilis to elimination levels.

For more information, visit: www.paho.org/hiv