Viral load is an indication of the amount of virus in the bloodstream in HIV infection. It also known as HIV viral load or plasma viral load and is an important means to monitor the progress of the disease and the success of treatment. Regularly monitoring the viral load, at least every 3 to 6 months, while on HAART (highly active antiretrovial therapy) is essential in the management of HIV/AIDS. The viral load is the amount of nucleic acid (HIV RNA) in the bloodstream and not the actual number of viruses.
In HIV infection, the virus injects its proteins (enzymes and RNA) into the CD4+ T-lymphocyte cells. The RNA is the blueprint of the virus that is used by the host’s protein-making apparatus. The proteins make up the RNA and enzymes for many more new viruses. In the viral replication process, the T-lymphocyte cell is destroyed and the number of viruses increases exponentially. CD4 count is a measure of the body’s CD4 T-lymphocyte levels and as it declines, the viral load increases. Read more on HIV and AIDS.
Meaning of Viral Load
What does the viral load mean?
HIV viral load is measured in nucleic acid copies per milliliter of blood (copies/mL). Since each virus in HIV infection contains two RNA copies, the number of virus particles is equivalent to half of the viral load value. The HIV RNA is sometimes used for early HIV screening (p24 antigen test) during the “window period” when HIV antibodies cannot be detected.
The viral load in conjunction with CD4 count is able to monitor the progression of the disease and how soon AIDS may set in. It is also an indication of the efficacy of treatment – if treatment is effective then the viral load will decline, if not then the viral load will continue to rise. The viral load can also serve as a means to identify when HAART should be started. HAART is commenced when the CD4 cell count is less than 350 cells/mm3, sometimes as low as 200 cells/mm3 or as high as 500 cells/mm3. Considering starting HAART based on the viral load, however, is not as simple and many doctors may advise patients on HAART with a viral anywhere between 10,000 to 30,000 copies/mL.
Normal Viral Load
What is a normal viral load in HIV?
There is no normal value for viral load. A person who is not HIV-positive does not have a viral load since the virus does not exist in the bloodstream. Therefore the reference range cannot be determined in a manner that is considered to be “normal”. Viral load can be said to be high, low or undetectable. The aim of treatment is to attain an undetectable level for the viral load.
High Viral Load
What is considered to be a high viral load?
A viral load exceeding 10,000 copies is considered to be high. Levels may be recorded in the tens of thousands, hundreds of thousands and even reach one million or more copies/mL. A viral load above 40,000 copies/mL is considered to be very high. These very high levels are seen in uncontrolled and untreated cases. However, categorizing the viral load is insignificant as the aim of therapy is to bring the viral load to the undetectable level or at least within the low range.
Low Viral Load
What is considered to be a low viral load?
A viral load below 500 copies/mL is considered as low. The aim of treatment is to maintain the viral load at this level if the the undetectable level cannot be attained. Very high viral loads that decline below 5,000 copies/mL can be considered as being low so sometimes the term ‘low’ is relative in this case. However, a level below 500 copies/mL is a good indication that viral replication has drastically slow or ceased, albeit temporarily, and the disease is not progressing further for now.
Undetectable Viral Load
What does an undetectable viral load mean?
An undetectable viral load is reported when the level drops to below 50 copies/ milliliter. This does not mean that the virus has been eradicated from the bloodstream or that the patient is “cured”. The viral RNA may just be below the threshold and cannot be detected. Eventually the viral load will rise again and regular monitoring even with an undetectable viral load is therefore essential. The aim of treatment is to maintain the viral load at undetectable levels as long as possible.