Viral load in HIV
Human immunodeficiency virus (HIV) is the virus that causes acquired immunodeficiency syndrome (AIDS). When a person is initially infected with HIV, the virus replicates — it produces more and more copies of itself. The main target of HIV is the CD4 cells, which are a type of white blood cell that fights infections. The virus enters the cells and uses them to replicate and spread throughout the body. It moves into the lymph nodes, spleen, and other parts of the body.
In the early stages of infection, there may not be any noticeable signs or symptoms of disease or only flu-like symptoms, although the virus is usually present in high amounts. Without treatment and even when there are no symptoms, the virus continues to replicate and the viral load will increase. HIV kills CD4 cells, so the number of CD4 cells will decrease as HIV infection progresses.
When a person is diagnosed, antiretroviral treatments for HIV (also called highly active antiretroviral therapy or HAART) are initiated to suppress the amount of HIV virus present in the blood, limiting its ability to replicate and reducing the risk of progressing to AIDS. If a person with HIV discontinues treatment or if it loses its efficacy, then the person’s HIV viral load can begin to increase again.
The HIV RNA test detects HIV virus genetic material and measures how many copies of HIV (viral load) are present in the blood at a particular time. It can track increases and decreases in HIV viral load and, in conjunction with a CD4 count, be used to evaluate treatment effectiveness. Blood is drawn from a vein in the arm for this test. No preparation is needed before testing.
Viral load vs CD 4 count
HIV viral load predicts how fast the disease will progress, while other tests, like the CD4 count, indicate how much damage the virus has already caused.
What is a viral load?
HIV viral load tests are reported as the number of HIV copies in a milliliter (copies/mL) of blood. If the viral load measurement is high, it generally indicates that HIV is present and replicating.
Your doctor can order a viral load test to assess the level of HIV in your body. It measures the number of HIV virus particles in a milliliter of your blood. Those particles are also known as “copies.”
A low viral load is a sign of the virus copying itself in low amounts in the body. According to AIDS.gov, HIV viral load is typically undetectable below levels of 40–75 copies/mL. The goal of HIV therapy is to lower your viral load below the detectable level.
Why is it important to consider multiple test results?
A single test result can only tell you so much about your CD4 levels, viral load, and overall health. The numbers often vary from one test to another. Preferably the same test should be used in follow up tests, because different tests may produce different results.
Also, after contracting HIV, there is a period when the virus makes several copies, leading to a viral load spike. Once your immune system responds to it, it will decrease to a base level. The time of day, any illnesses you have, and recent vaccinations can also affect your CD4 count and viral load.
Changes in viral load can often be more important during HIV monitoring than a single test result. An increasing viral load indicates either that the infection is getting worse or that the virus has developed resistance to the drugs that is being used for therapy and is no longer effective. A decreasing viral load indicates improvement, treatment effectiveness, and suppression of the HIV infection.
As a result, it’s important to consider trends in your test results, rather than just individual test results.
Viral load and sexual transmission of HIV
If you have a high viral load in your blood, then you might also have a high viral load in other body fluids, including your semen or vaginal fluid. In the first few weeks after contracting HIV, viral load is usually extremely high. People with high viral loads are more infectious and can pass HIV on more easily. On the other hand, if HIV in your blood is undetectable, it is likely to be undetectable in your semen, vagina fluid or rectum as well. Having an undetectable viral load means that the risk of HIV being passed on is extremely low.