Last reviewed: 30 Oct 2023
Last updated: 25 Oct 2022

This page compiles our content related to HIV. For further information on diagnosis and treatment, follow the links below to our full BMJ Best Practice topics on the relevant conditions and symptoms.



HIV infection is a pandemic infectious disease whose impact on societies is without precedent. Globally, an estimated 37.7 million people were living with HIV at the end of 2020, with 1.5 million people newly infected.[4] It 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.

Pregnancy in women living with HIV is complicated not only by HIV infection itself but also by the medical and psychosocial comorbidities associated with HIV. HIV infection in pregnancy poses a threat to maternal immune health and can lead to perinatal transmission of HIV in utero, intrapartum, or through breastfeeding postnatally.

The administration of antiretroviral therapy to HIV-negative people who may have been occupationally or sexually exposed to HIV. Once exposed to HIV, there may be a brief period before the infection is established, during which antiretroviral therapy may successfully prevent viral replication.[5][6]

Clinical syndromes that arise as a consequence of impaired immunity in advanced stages of HIV infection. These illnesses tend to occur most often in patients who have untreated HIV infection or who fail to benefit from antiretroviral therapy. Tuberculosis, Pneumocystis jirovecii pneumonia, candidiasis, cryptococcosis, toxoplasmosis, cytomegalovirus, and Mycobacterium avium complex (MAC) infections are among the HIV-related opportunistic infections often encountered in clinical practice.[3]

One of the most common AIDS-defining illnesses in children, adolescents, and adults.[7] It is an infection of the lung caused by the fungal organism Pneumocystis jirovecii (formerly known as Pneumocystis carinii). Typically, it causes clinical disease in severely immunocompromised patients, such as HIV-positive patients with CD4 cell counts <200 cells/microliter, hematopoietic cell transplant patients, solid-organ transplant patients, or patients on chronic immunosuppressive therapy.

One of the most common causes of death among patients with AIDS worldwide.[3] It is an infectious disease caused by Mycobacterium tuberculosis. In many patients, M tuberculosis becomes dormant before it progresses to active tuberculosis. It most commonly involves the lungs and is communicable in this form, but may affect almost any organ system including the lymph nodes, central nervous system, liver, bones, genitourinary tract, and gastrointestinal tract.

Mycobacterium avium complex (MAC), also known as Mycobacterium avium-intracellulare (MAI), consists of 2 mycobacterium species, M avium and M intracellulare. It traditionally causes 3 disease syndromes: pulmonary disease, cervical lymphadenitis, and disseminated disease. People living with HIV with a CD4 count <50 cells/microliter are at increased risk of infection.[3]

Caused by the protozoan parasite Toxoplasma gondii. Cats are the definitive hosts for the parasite. Humans are intermediate hosts, and become infected by ingesting uncooked meat infected with tissue cysts (bradyzoites), by ingestion of other food or water contaminated with oocysts, or by transplacental spread of tachyzoites. Infection in humans is lifelong and often asymptomatic, unless a patient becomes immunosuppressed. People living with HIV with CD4 counts <50 cells/microliter are at greatest risk of symptomatic disease.[3]

An opportunistic fungal infection caused by Cryptococcus species. Cryptococcus neoformans var. grubii and Cryptococcus neoformans cause morbidity and mortality, especially in immunosuppressed populations, such as those with HIV. Patients with compromised cell-mediated immunity are at higher risk of acquiring cryptococcosis, particularly those with CD4 cell counts <100 cells/microliter.[3]

Cytomegalovirus (CMV) is a ubiquitous beta-herpes virus that infects the majority of humans. Primary infection in individuals with normal immune function is usually asymptomatic. After primary infection, CMV establishes a state of lifelong latency in various host cells, with periodic subclinical reactivations that are controlled by a functioning immune system. When reactivation (or primary infection) occurs in patients with severely compromised immune function (transplant patients, or patients with AIDS with a CD4 count <50 cells/microliter), uncontrolled CMV replication often ensues, which leads to the clinical manifestations characterized by fever, bone marrow suppression, and tissue-invasive disease.[8][9]

One of the most diagnosed opportunistic infections among people living with HIV, particularly in patients with a CD4 count <200 cells/microliter.[3] It involves a local infection of oral tissues by yeasts of the genus Candida, mostly C albicans. Although Candida are considered normal flora in the gastrointestinal and genitourinary tracts in humans, they are capable of local infection of mucus membranes (oropharyngeal candidiasis, oesophagitis, vulvovaginitis), focal invasion (endophthalmitis, meningitis, endocarditis), and dissemination (candidemia).

The most common neoplasm arising in people with HIV. It is a low-grade vasoformative neoplasm associated with human herpesvirus-8 (HHV-8, also known as Kaposi sarcoma-associated herpesvirus).[10] Lesions frequently involve mucocutaneous sites, but may become more extensive to involve the lymph nodes and visceral organs. Skin lesions evolve from an early patch, to a plaque, and later to ulcerating tumor nodules.

Cutaneous manifestations often reflect immune status and may offer insight into the long-term prognosis of HIV-infected patients. The etiologies of different diseases involving the entire spectrum of skin and HIV vary, but a useful etiologic distinction to note is that some skin diseases are fairly specific to HIV (e.g., Kaposi sarcoma, oral hairy leukoplakia, papular pruritic eruption of HIV, HIV photodermatitis), and other skin diseases may appear in non-HIV-infected populations but have altered presentation with HIV.

Causes of altered mental status in HIV infection include both acutely presenting conditions (which often represent HIV-related opportunistic infection or associated systemic illness) and more progressive neurocognitive disease or psychological comorbidity. Neuropsychological issues may arise as a direct effect of HIV infection: for example, as part of a spectrum of HIV-associated neurocognitive disorders or as a psychiatric comorbidity (e.g., depression or alcohol/substance abuse).



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