Hepatitis A Virus (HAV)

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🔸Causes: Hepatitis A
🔸Transmission: Through ingestion of food or water contaminated with feces from an infected person (fecal-oral route)

Disease Characteristics
🔸Acute phase: Most cases resolve spontaneously
🔸Does not become chronic
🔸Prevention: Vaccination provides effective immunity and is widely used

Laboratory Testing
1.Serological Tests
🔸Anti-HAV IgM: Detects acute infection. Appears 1–2 weeks before symptom onset and persists for about 3–6 months. 
👉A Positive result indicates an ongoing acute HAV infection.

🔸Anti-HAV IgG: Indicates immunity to HAV. Appears after infection or vaccination and persists lifelong. 
👉A Positive result indicates previous infection or successful vaccination and provides long-term immunity.

Summary:
🔸Anti HAV IgM → Recent infection
🔸Anti HAV IgG → Long-term immunity

2. Molecular Tests
🔸HAV RNA detection (RT-PCR): Detects viral genetic material in blood or stool.
🔸Used to confirm acute infection, especially when IgM is not yet detectable.
🔸Commonly used in reference or research laboratories.

3. Biochemical Tests
🔸Assess liver function in conjunction with HAV diagnosis.
🔸Commonly altered parameters:
🔸ALT (Alanine aminotransferase): Markedly elevated
🔸AST (Aspartate aminotransferase): Elevated
🔸Total Bilirubin / Direct Bilirubin: Elevated → causes jaundice (yellow skin/eyes)

Note: 
🔸ALT is usually higher than AST in acute hepatitis.

Diagnostic Approach for HAV
🔸Suspected acute HAV infection → test Anti-HAV IgM
🔸Assess Immunity → test Anti-HAV IgG
🔸Confirm Acute Infection (if IgM is unclear) → RT-PCR
🔸Evaluate liver injury → test ALT, AST, Bilirubin

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