Acute HIV encephalitis (during primary HIV infection)

Page most recently updated 7 September 2026

This page focuses on the reported psychiatric associations, which may be the initial presenting manifestation, and on other clinical features that may assist the psychiatrist or primary care physician in identifying the underlying diagnosis, considered through the lenses of the diagnostic lenses framework.

Acute HIV encephalitis (during primary HIV infection) is a rare but potentially severe neurological manifestation of acute HIV infection, in which early CNS involvement can produce meningoencephalitis, encephalopathy, and neuropsychiatric manifestations. A distinctive presentation may include acute neuropsychiatric features, headache or meningitic symptoms, and a concurrent acute retroviral syndrome (a mononucleosis-like illness) with features such as fever, pharyngitis, rash, and lymphadenopathy, particularly when accompanied by cytopenias.

Importantly, a negative HIV antibody test does not completely exclude recent HIV infection, particularly during the first 3 months after acquisition. If acute HIV encephalitis is suspected, HIV antigen testing should be performed in serum and HIV RNA (PCR) testing considered; CSF should also be tested for HIV, particularly with CSF HIV RNA (PCR), as CNS infection may occur during the seronegative phase.

Exposure clues may include recent sexual exposure to HIV, particularly condomless sexual contact or contact with a partner with known or possible HIV infection, as well as sharing needles, syringes, or other injection equipment. Acute HIV infection typically occurs within the first several weeks after acquisition, and neurological manifestations may occur during this period, sometimes before HIV infection has been recognized.

It can present with psychiatric features such as apathy, behavioural change, irritability, impaired concentration, executive dysfunction, cognitive impairment, and agitation, as well as psychotic symptoms which may occur in the absence of delirium.

Other characteristic features include severe headache, fever, meningism, nausea and vomiting, seizures, focal neurological deficits, cranial neuropathies, peripheral neuropathy, myelopathic features, and, in severe cases, coma or fulminant encephalopathy. Acute HIV meningoencephalitis may produce a lymphocytic CSF pleocytosis with elevated protein and may occur with normal structural neuroimaging. Most reported cases recover well following initiation of antiretroviral therapy.

From a multisystemic lens perspective, clinical features in other body systems include (but are not limited to):

  • Hematologic: Leukopenia, thrombocytopenia, lymphopenia, or other transient hematologic abnormalities may occur during acute HIV infection.

  • Respiratory: Pharyngitis, cough, and, less commonly, dyspnoea may occur as part of the acute retroviral syndrome.

  • Hepatobiliary: Mild elevations of transaminases are common during acute HIV infection and may accompany the acute retroviral syndrome.

  • Dermatologic: A diffuse maculopapular or other nonspecific rash may occur during acute HIV infection.

  • Gastrointestinal: Diarrhoea, nausea, vomiting, abdominal discomfort, and oral ulcers may occur as part of the acute retroviral syndrome.

  • Musculoskeletal: Myalgia and arthralgia are common systemic manifestations of acute HIV infection.

Early diagnosis is important because acute HIV encephalitis or meningoencephalitis can occasionally be severe or life-threatening, while prompt recognition of acute HIV infection allows early antiretroviral therapy and appropriate management of neurological complications.

Selected references and further reading — Multisystemic lens

Cardinal RN, Bullmore ET. The diagnosis of psychosis. Cambridge: Cambridge University Press; 2011.

Sachdev PS, Keshavan MS, editors. Secondary schizophrenia. Cambridge: Cambridge University Press; 2010.

Levenson JL, editor. The American Psychiatric Association Publishing textbook of psychosomatic medicine and consultation-liaison psychiatry. 3rd ed. Washington (DC): American Psychiatric Association Publishing; 2019.

Stern TA, Beach SR, Smith FA, Freudenreich O, Vranceau AM, Fava M, editors. Massachusetts General Hospital handbook of general hospital psychiatry. 8th ed. Philadelphia: Elsevier; 2025.

Arciniegas DB, Yudofsky SC, Hales RE, editors. The American Psychiatric Association Publishing textbook of neuropsychiatry and clinical neurosciences. 6th ed. Washington (DC): American Psychiatric Association Publishing; 2018.

Agrawal N, Faruqui R, Bodani M, editors. Oxford textbook of neuropsychiatry. Oxford: Oxford University Press; 2020.

Boland R, Verduin M, editors. Kaplan and Sadock's comprehensive textbook of psychiatry. 11th ed. Philadelphia: Wolters Kluwer; 2024.

Loscalzo J, Fauci AS, Kasper DL, Hauser SL, Longo DL, Jameson JL, editors. Harrison's principles of internal medicine. 22nd ed. New York: McGraw Hill; 2025.