Overview
Hepatitis A virus (HAV) is a non-enveloped, positive-sense RNA virus belonging to the Picornaviridae family. It is resistant to heat and cold and primarily infects the liver.
HAV causes hepatitis A, an acute liver disease transmitted mainly through the faeco-oral route. The virus infects hepatocytes, leading to inflammation of the liver and elevation of liver enzymes. Virus particles are excreted through bile into the feces. HAV (Hepatitis A Virus)
Transmission and Endemic Nature
Hepatitis A virus is transmitted mainly through contaminated food and water. Consumption of undercooked shellfish and person-to-person contact are common routes of spread.
Poor sanitation and hygiene significantly increase transmission. The infection is endemic in many developing countries, with outbreaks commonly reported in communities. Travelers to endemic areas are at higher risk.
Pathogenesis and Clinical Features
Hepatitis A virus infection is an acute, self-limiting disease with an incubation period ranging from 15 to 50 days. Chronic infection is not seen with HAV.
Common symptoms include fatigue, fever, malaise, jaundice, nausea, vomiting, abdominal pain, dark urine, and pale stools. A rare but serious complication is fulminant hepatitis.
Importance of HAV Testing
Hepatitis A virus testing helps confirm acute hepatitis A infection and allows for timely diagnosis. Early detection helps prevent severe liver complications.
Testing also differentiates HAV from other viral hepatitis infections and helps determine immunity status following past infection or vaccination. It plays an important role in outbreak investigations and epidemiological studies.
HAV Antibody Response
IgM anti-HAV antibodies appear during the acute phase of infection, peak shortly after liver enzyme elevation, and usually disappear within 3 to 6 months.
IgG anti-HAV antibodies appear shortly after IgM and persist for decades, indicating past infection or immunity. HAV RNA detection by RT-PCR identifies the viral genome and is mainly used in outbreaks or research settings.
Methods of Detection
HAV infection can be detected using immunochromatographic rapid tests, ELISA, chemiluminescent immunoassays, and RT-PCR.
Rapid tests and immunoassays are commonly used for antibody detection, while RT-PCR is more sensitive during early infection, especially before antibody development.
Interpretation of Rapid Test
A positive result shows both control and test bands, indicating the presence of anti-HAV antibodies. A negative result shows only the control band.
If the control band does not appear, the test is considered invalid and must be repeated using a new device.
HAV RT-PCR and Infection Phases
RT-PCR is particularly useful in the early phase of HAV infection when antibodies may not yet be detectable. It can be performed on serum or stool samples.
HAV infection progresses through early, overt, recovery, and relapse phases. PCR is recommended during the early phase, while antibody testing is useful in later stages.
Limitations and Clinical Considerations
Serological tests are qualitative and do not reflect antibody concentration. A negative result does not completely rule out infection, especially if testing is done early.
False-negative or false-positive results may occur due to assay interference, cross-reactivity, or persistence of IgM antibodies. Specialized equipment and careful interpretation are required, particularly for molecular tests.
