Chronic infection by HIV (a retrovirus) that destroys CD4+ T cells, causing progressive immunodeficiency. Untreated, it progresses to AIDS with opportunistic infections.
Without treatment, HIV infection is uniformly fatal as the immune system collapses. With modern therapy, however, it has become a manageable chronic illness—patients with HIV can live long, healthy lives on ART.
Acute (primary infection): ~2–4 weeks after exposure, a mononucleosis-like illness often occurs (fever, sore throat, lymphadenopathy, rash). Some may be asymptomatic or have mild flu-like symptoms.
Chronic phase: An asymptomatic latency that can last years. Persistent generalized lymphadenopathy may be present. Gradual immune decline leads to candidal infections (e.g., oral thrush) or zoster outbreaks as early clues.
AIDS (advanced HIV): Defined by CD4 count <200 or an AIDS-defining illness. Patients develop severe opportunistic infections (e.g., Pneumocystis pneumonia, Kaposi sarcoma, TB, Cryptococcus meningitis, CMV retinitis).
Follow the HIV testing algorithm: screen with a 4th-generation HIV-1/2 Ag/Ab combo test (detects p24 antigen ~14 days post-exposure). If positive, perform a confirmatory differentiation immunoassay to distinguish HIV-1 vs HIV-2.
If acute infection is suspected (exposure within ~2 weeks) or initial test is indeterminate, obtain an HIV RNA NAAT for detection (RNA can be positive as early as 5–10 days post-transmission).
Upon diagnosis, get baseline CD4 count and HIV viral load; screen for coinfections (e.g., TB, hepatitis B/C) and check HIV genotype for drug resistance. Monitor CD4 and viral load regularly to track treatment response (goal = undetectable viral load).
Prevent opportunistic disease: start prophylaxis when CD4 falls below key thresholds (e.g., TMP-SMX if CD4 <200 for PCP). Keep routine vaccines up-to-date (avoid live vaccines if CD4 is very low).
Prevent transmission: counsel on safe sex and needle practices. Offer PrEP (e.g., tenofovir-emtricitabine) to high-risk HIV-negative individuals and give PEP within 72 hours after high-risk exposures. In pregnancy, ensure maternal ART to minimize vertical transmission.
Condition
Distinguishing Feature
Infectious mononucleosis (EBV/CMV)
EBV causes fever, pharyngitis, and lymphadenopathy in young adults (Monospot test positive). CMV can cause a mono-like syndrome (heterophile negative). Neither typically presents with diffuse rash.
Influenza
Acute flu with high fever, myalgias, and cough. Often seasonal; typically lacks lymphadenopathy or rash and symptoms resolve in <2 weeks.
Secondary syphilis
Systemic Treponema pallidum infection causing fever, generalized rash (often including palms/soles), and mucous patches. Distinguished by a history of genital ulcer and positive syphilis serologies.
Antiretroviral therapy (ART) for all patients, started as soon as possible after diagnosis. Standard regimens use a combination of 3 drugs (e.g., 2 NRTIs + 1 integrase inhibitor). Lifelong strict adherence is crucial.
Goals of therapy: achieve an undetectable viral load (prevents disease progression and transmission) and restore immune function (increase CD4 count). When viral load is undetectable, risk of sexual transmission is effectively zero (U=U principle).
Manage opportunistic diseases: provide prophylactic antibiotics at specific CD4 cutoffs (e.g., TMP-SMX for PCP, azithromycin for MAC) and treat any active infections aggressively (e.g., itraconazole for Histoplasma, etc.). In advanced cases, monitor for IRIS (inflammatory flare) after starting ART.
AIDS definition: CD4 count <200 or any AIDS-defining illness (e.g., Pneumocystis pneumonia, Kaposi sarcoma).
CD4 count thresholds for OIs: <200 for PCP pneumonia, <100 for Toxoplasma brain abscess or Cryptococcus, <50 for MAC and CMV retinitis.
Neonatal diagnosis: maternal HIV IgG crosses placenta (persists ≤18 months), so use virologic tests (PCR) in infants—HIV antibody tests are unreliable.
Severe opportunistic infection in an HIV patient – e.g., Pneumocystis pneumonia with hypoxia, cryptococcal meningitis, or cerebral toxoplasmosis – is a medical emergency requiring prompt treatment and urgent initiation of ART.
Blurred vision or floaters in a patient with AIDS (CD4 <50) → suspect CMV retinitis, a treatable cause of blindness. Urgent ophthalmologic therapy is needed to prevent permanent vision loss.
Possible exposure or acute retroviral syndrome → HIV test (4th-gen Ag/Ab).
Initial screen positive → do HIV-1/HIV-2 antibody differentiation assay to confirm type.
If initial test negative but high suspicion (early window period) → perform HIV RNA test (detects infection ~1–2 weeks sooner).
Confirmed HIV diagnosis → baseline labs (CD4 count, viral load, resistance testing, co-infection screen) → start ART promptly.
Follow-up: monitor HIV RNA (expect undetectable in 6 months) and CD4 count; add OI prophylaxis when CD4 drops below thresholds; ensure adherence and regular care.
Young adult with fever, sore throat, generalized rash ~3 weeks after unprotected sex → acute HIV infection (acute retroviral syndrome).
Patient with untreated HIV presents with weight loss, chronic diarrhea, oral thrush, and Pneumocystis pneumonia (dyspnea, hypoxia) → indicates AIDS (CD4 likely <200).
HIV-positive patient with purple skin lesions (Kaposi sarcoma) or progressive vision loss (CMV retinitis) → an AIDS-defining condition signaling advanced disease.
Case 1
A 25‑year‑old man presents with 2 weeks of fever, painful throat, and a generalized rash. He mentions a new sexual partner and inconsistent condom use. Exam shows cervical lymphadenopathy and oral ulcers. A Monospot test for heterophile antibodies is negative.
Graph showing HIV viral load (red) and CD4+ T-cell count (blue) over an untreated HIV infection. Initial acute phase features a spike in viral load and drop in CD4 count, followed by a latent period and then progression to AIDS.
