HIV infection

HIV infection is believed to have peaked in the late 1990s and to have stabilised recently. Globally, an estimated 38.4 million people were living with HIV at the end of 2021, with 1.5 million people newly infected.

Most people are infected through sexual contact, before birth or during delivery, during breastfeeding, or when sharing contaminated needles and syringes.

Diagnosis is established using an HIV antibody test and confirmed using a more specific test. Patients should be clinically staged according to World Health Organization or US Centers for Disease Control and Prevention criteria.

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

Pre-exposure prophylaxis with daily oral antiretroviral therapy or long-acting intramuscular cabotegravir reduces the risk of HIV 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.

Diagnosis and management varies between resource-intensive settings and resource-limited settings.

HIV infection 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.

At the initial consultation with the medical practitioner, an infected patient may be 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.

AIDS (a syndrome of a constellation of infections, conditions, or malignancies) occurs as a result of HIV infection, and usually develops over 10-15 years.​[1]World Health Organization. HIV/AIDS: online QA. Nov 2022 [internet publication]. https://www.who.int/news-room/questions-and-answers/item/hiv-aids

This topic focuses on the diagnosis and initial management of non-pregnant adults with HIV infection. The management of treatment-experienced patients and special patient populations is beyond the scope of this topic. See Overview of HIV for details of our other topics.