HIV in adults

HIV is believed to have peaked in the late 1990s and to have stabilised recently. An estimated 40 million people were living with HIV at the end of 2023 globally, with 1.3 million new infections.

Most adults are infected through sexual contact or injection drug use.

Diagnosis is established using an HIV antibody/antigen immunoassay. An HIV-1/HIV-2 antibody differentiation immunoassay is recommended if the initial test is reactive, in order to confirm the diagnosis.

Guidelines recommend that all patients with HIV, regardless of CD4 count, start antiretroviral therapy (ART) as soon as possible.

Pre-exposure prophylaxis reduces the risk of infection and is recommended in sexually active adults and people who inject drugs and who are at substantial ongoing risk of HIV exposure and acquisition.

HIV is caused by a retrovirus that infects and replicates in human lymphocytes and macrophages, eroding the integrity of the human immune system over a number of years, culminating in immune deficiency and a susceptibility to a series of opportunistic and other infections as well as the development of certain malignancies.

A patient with HIV may present at any stage of the natural history from acute to chronic infection, ranging from asymptomatic through to severely unwell. The initial assessment is key for prognosis and formulation of short- to long-term management plans.

Primary infection refers to the first 6 months following HIV acquisition and is associated with an evolving HIV antibody response and high-level plasma HIV viremia.[1]Fidler S, Fox J. Primary HIV infection: a medical and public health emergency requiring rapid specialist management. Clin Med (Lond). 2016 Apr;16(2):180-3. https://www.rcpjournals.org/content/clinmedicine/16/2/180 http://www.ncbi.nlm.nih.gov/pubmed/27037390?tool=bestpractice.com

AIDS (a syndrome of a constellation of infections, conditions, or malignancies based on set criteria) occurs as a result of chronic infection and increasing immune depletion over time, and usually develops over 10-15 years in the absence of treatment, but sometimes longer.​[2]World Health Organization. HIV/AIDS: online QA. Jul 2024 [internet publication]. https://www.who.int/news-room/questions-and-answers/item/hiv-aids

This topic focuses on the diagnosis and initial management of adults with HIV-1 infection. The management of HIV-2 infection, treatment-experienced patients, special patient populations (including children and adolescents, and pregnant and breastfeeding women), and opportunistic infections is beyond the scope of this topic. See Overview of HIV for other available HIV topics.