Q: What is viral load in the context of AIDS. How is it measured and what is the significance of CD4 & CD8 counts?

A:Viral load is a measure of viral replication in the body. It indicates viral activity and, in effective antiviral therapy such as HAART, it comes down to unmeasurable levels. This does not mean that all the virus has been killed. With the drug regimes currently available, the virus reactivates when therapy is stopped, and there is also a chance of resistance developing. That is why it is important to continue therapy once started. It is measured in the blood. CD4 and CD8 are counts done of two of the types of the white cells in the blood that are responsible for immune function. Reduction in these cell counts occur when they are damaged by HIV virus. Reduction in CD4 cell activity suggests that the ability of the body to resist infection is impaired. Generally, a CD4 cell count below 200 is an indication for starting ARV treatment. Both viral load and CD cell count are used to monitor the effectiveness of ARV treatment.