In this article, we discuss what viral load means for people living with HIV and their partners, the links between viral load and CD4 levels, and how doctors test and monitor these levels.
What is HIV viral load?
The viral load is the amount of HIV in a person's blood.
Doctors define the viral load as the number of HIV copies in a milliliter of blood (copies/ml).
Doctors initially use the viral load to check the status of HIV after diagnosis, then to monitor the success of HIV treatments.
When a person contracts HIV the virus replicates in their blood. The more copies of the virus there are, the higher a person's viral load.
If there is a high number of copies in the blood, this suggests that there is also a high number in other bodily fluids, such as vaginal fluid and semen.
The main aim of HIV treatments is to reduce the viral load to the point where there are so few copies of the virus left that it is undetectable in the blood.
Before treatment: Detectable viral load
When doctors say a person has detectable levels of HIV in a viral load test, it means there is a significant amount of HIV in their blood. This level will vary based on the stage of the condition and the stage of treatment.
On first diagnosis of HIV, a person's viral load is typically high. Shortly after contracting HIV, the viral load will drop as the immune system starts to fight the virus.
Without treatment, the viral load will rise again as the virus starts to destroy specific immune system cells known as CD4 cells.
After treatment: Undetectable viral load
Antiretroviral therapy aims to reduce a person's viral load to undetectable levels. This is known as viral suppression.
After starting antiretroviral therapy, a person's HIV viral load tests will come back with low numbers. When this occurs, the treatment is working, and HIV is no longer progressing. With a lower viral load, the chances of transmitting the virus to others become lower.
According to the United States Centers for Disease Control and Prevention (CDC), an undetectable viral load means less than 200 copies/ml.
An undetectable viral load means that a person has effectively zero risk of sexually transmitting the virus to an HIV-negative partner.
Large-scale research has shown that when HIV is undetectable, it is virtually untransmittable, even through condomless sex.
This concept is known as U=U, which stands for undetectable = untransmittable.
Almost everyone who starts antiretroviral treatment finds a drug regimen that works within 6 months. It will take longer to find the right treatment in around 1 in 6 people because of their tolerance or adherence to the regimen.
HIV is a chronic condition. When the virus becomes undetectable, some copies still remain in the blood. People must continue to take their HIV medication as prescribed to keep their viral load undetectable.
When controlled, people living with HIV can experience the same quality of life as a person without HIV.
Viral load and CD4 levels
When someone contracts HIV, the virus begins to take over specific cells in the immune system, called CD4 cells.
When the CD4 cells replicate, the HIV cells inside them also replicate. HIV hijacks the cellular machinery of CD4 cells to reproduce and shed more HIV, which means the viral load increases.
As the HIV viral load increases, the number of healthy CD4 cells decreases as they are destroyed creating HIV copies.
Treatment aims to produce a low viral load and a high CD4 count. When a person has achieved this, their HIV is well controlled.
A low or undetectable viral load means the virus is not progressing. It also means that HIV is not attacking the immune system as actively. This gives the immune system the chance to rebuild its healthy cell count. As a result, the number of CD4 cells in the person's body will increase as their viral falls.
When should people get a viral load test?
A doctor can check the viral load by conducting a blood test.
A doctor will usually test a person's viral levels when they first diagnose HIV. Doctors will recommend an HIV test if someone presents symptoms of HIV or if they may have come into contact with the virus.
People living with HIV will have repeat viral load tests throughout their lives to monitor the condition. They should get tested once every 3 to 4 months during treatment.
Additionally, a person should get tested due to any alteration in their medication or if their symptoms change.
Low or undetectable viral counts are strong indicators that the person's treatment is working. If a test reveals that the viral load is increasing, a doctor may need to adjust their treatment.
Viral load test procedure
A doctor can test the viral load using a simple blood test. No preparation is needed.
The doctor or technician will draw a small amount of blood and send the sample to the labs to test the viral load and CD4 count.
It often takes a few days for the results to come back. Once they are back, the doctor will likely call to discuss the results with the individual.
HIV viral load refers to the amount of HIV present in a person's blood. Higher numbers typically indicate that they have not yet received HIV treatment, or that their treatment is not effective.
People living with HIV will also receive tests to check their CD4 count. These checks measure the number of cells the immune system produces. Higher numbers of CD4 cells indicate that the person's immune system is stronger and better able to fight off infections.
When the viral load reaches less than 200 copies/ml of blood, doctors consider that HIV is undetectable. Though copies of the virus remain in the blood, undetectable levels mean that a person cannot transmit the virus to others. When people achieve this, they can live the same quality of life as those without HIV.