Viral load

Viral Load

A viral load is a numerical expression of the quantity of virus in a given volume. It is often expressed as viral particles, or infectious particles per mL depending on the context. This measurement is significant in both diagnostic and therapeutic contexts, particularly in relation to HIV and Hepatitis C.

Measurement

Viral load is typically measured with a polymerase chain reaction (PCR) test, which amplifies the viral RNA or DNA in a sample to detectable levels. The result is then quantified and expressed as copies per milliliter (copies/mL). The sensitivity of these tests can vary, but most can detect levels as low as 50 copies/mL.

Clinical Significance

In the context of diseases such as HIV and Hepatitis C, viral load is a crucial indicator of disease progression and the effectiveness of antiviral therapy. A high viral load often indicates active viral replication and progression of the disease. Conversely, a low or undetectable viral load suggests that the disease is well-controlled, either naturally or through treatment.

HIV

In HIV infection, viral load testing is a key part of monitoring disease progression. It is used alongside CD4 cell count to determine the stage of the disease and the timing of antiretroviral therapy (ART). A high HIV viral load is associated with a faster progression to AIDS and a higher risk of transmission.

Hepatitis C

In Hepatitis C infection, viral load does not correlate with disease severity but is used to monitor the effectiveness of treatment. A sustained virologic response (SVR), defined as an undetectable viral load 12 weeks after completion of treatment, is considered a cure.

See Also

• Virus quantification
• HIV/AIDS
• Hepatitis C
• Polymerase chain reaction

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