Write a short note on acute HIV (primary) infection.

Definition

Acute HIV infection — also called primary HIV infection or the acute retroviral syndrome — is the illness occurring 2–6 weeks after HIV acquisition, during the phase of explosive viral replication before an effective immune response develops. It is symptomatic in an estimated 50–90% of those infected, but is very frequently missed because it resembles a common viral illness.

Pathophysiology

1. The virus crosses the mucosal barrier, replicates in local dendritic cells and CD4 lymphocytes, and reaches regional lymph nodes.

2. Massive viral dissemination occurs, with plasma viral loads often exceeding a million copies/mL — far higher than at any later stage.

3. Profound but transient fall in the CD4 count, with massive depletion of gut-associated lymphoid tissue (GALT) CD4 cells — damage that is never fully repaired and underlies chronic immune activation.

4. The latent reservoir is established within days — which is why even very early treatment does not cure the infection.

5. The emerging CD8 cytotoxic and antibody response then partially controls viraemia, which settles to the individual's "viral set point" — a strong predictor of the subsequent rate of progression.

Clinical Features

The illness resembles infectious mononucleosis and typically lasts 1–3 weeks, resolving spontaneously.

Common features:

• Fever (the commonest, in over 75%) and profound fatigue
• Generalised lymphadenopathy — particularly cervical, axillary and occipital
• Pharyngitis, often with painful mucocutaneous ulceration of the mouth, oesophagus or genitals — a highly suggestive feature
• Maculopapular rash — non-pruritic, on the trunk, face, palms and soles, appearing 2–3 days after fever onset
• Myalgia, arthralgia, headache with retro-orbital pain
• Night sweats, weight loss, anorexia
• Nausea, vomiting, diarrhoea

Less common but important:

• Aseptic meningitis, encephalitis, Guillain–Barré syndrome, Bell's palsy, brachial neuritis — neurological involvement occurs early
• Oral or oesophageal candidiasis and, rarely, PCP — reflecting the transient severe CD4 depletion
• Hepatosplenomegaly, jaundice

Laboratory findings: lymphopenia followed by lymphocytosis with atypical lymphocytes, thrombocytopenia, transaminitis — a picture easily attributed to any viral fever.

Diagnosis — the Key Point

Standard antibody tests are typically NEGATIVE during acute infection, because seroconversion has not yet occurred — this is the "window period". Diagnosing acute HIV therefore requires tests that detect the virus itself:

Approach: if acute HIV is suspected with a negative or indeterminate antibody test, request a fourth-generation assay and an HIV RNA test, and repeat antibody testing at 4–6 weeks and 3 months to document seroconversion. A very high viral load with a negative or evolving antibody result confirms the diagnosis.

Exclude the differentials in parallel: EBV and CMV serology, VDRL/RPR and specific treponemal test, dengue NS1 and serology, hepatitis serology, malaria smear, and a drug history.

Management

• Start antiretroviral therapy immediately — treatment during acute infection is strongly recommended. It limits the size of the viral reservoir, preserves gut-associated lymphoid tissue and immune function, lowers the viral set point, reduces the severity and duration of the illness, and prevents onward transmission at a time when infectiousness is at its highest.
• Supportive care for the acute illness — antipyretics, fluids, analgesia.
• Counselling — this is a difficult moment for the patient, who has usually just learned their diagnosis during an acute illness; provide psychological support, confidentiality, and clear explanation that HIV is now a chronic treatable condition with normal life expectancy on treatment.
• Partner notification and testing, with support; offer PrEP or PEP to partners as appropriate.
• Advise strict prevention of transmission during this period — infectiousness is extremely high because of the enormous viral load, and a substantial proportion of onward transmissions occur from people in the acute phase who do not yet know they are infected.
• Baseline workup and screening for co-infections as for established HIV.