What is "viral load"?
When healthcare providers discuss your "viral load," they are talking about the level of HIV in your blood. Knowing your viral load helps your provider to monitor your HIV disease, decide when to start treatment, and determine whether or not your HIV medications are working once you begin taking them.
There is usually a relationship between your viral load and the number of CD4 cells you have. Typically, if your viral load is high, your CD4 count will be low—making you more vulnerable to opportunistic infections. The antiretroviral medications you may take for your HIV disease work to keep HIV from reproducing in your body. This lowers your viral load and protects your immune system.
"Normal" viral load?
There really is no such thing as a "normal" viral load. People who aren’t infected with HIV have no viral load at all, so there’s no "normal" range for reference, as there is with many other lab tests (including CD4 counts).
Viral load testing looks for the number of virus particles in a milliliter of your blood. These particles are called "copies."
The goal of HIV treatment is to help move your viral load down to undetectable levels. In general, your viral load will be declared "undetectable" if it is under 40-75 copies in a sample of your blood (the exact number depends on the lab performing the test).
Changes in viral load
Your viral load changes over time. Typically, after you are first infected with HIV, your viral load will be extremely high—sometimes numbering in the millions in one blood sample. But your immune system responds and eventually brings your viral load back to a set point.
In general, your viral load continues to remain at low levels early in the course of your HIV disease, once the initial infection period has passed. It does begin to increase over time, however—eventually destroying more and more CD4 cells, until your CD4 count begins to show major damage to your immune system. At this point, treatment becomes necessary.
Viral Load Testing—When and How Often?
Your HIV healthcare provider will probably order a viral load test at your first visit after you are diagnosed, in order to establish a baseline level. After that, you will probably have a viral load test every 3–6 months, before you begin a new HIV medication, and 2–8 weeks after starting or changing therapies.
The trend of your viral load (whether it’s rising or falling) over time is what’s really important—not an individual test result.
Viral Load and Beginning HIV Treatment
For most healthcare providers, your CD4 count will be the major factor in deciding whether to recommend that you begin treatment for your HIV disease. Federal HIV treatment guidelines recommend that you begin treatment when your CD4 count falls below 350 cells/mm3.
But because of the strong association between increased viral load and increased destruction of CD4 cells, some providers may decide to start treatment based on your viral load alone.
Viral Load and Transmission of HIV
Studies have found that having a low viral load greatly decreases the risk that you will pass HIV to someone else through sexual contact.
But having a low viral load does not guarantee that you won’t transmit HIV to someone else. Even when the viral load in your blood is undetectable, HIV can still exist in semen, vaginal and rectal fluids, breast milk, and other parts of your body.
You should continue to take steps to prevent HIV transmission, even when your viral load is undetectable. You can protect your partner(s) by using condoms consistently and correctly for all sexual contact.
Fact Sheets & Print Materials
- AIDSinfo - Fact Sheet: Is My Treatment Regimen Working?
Related Topics on AIDS.gov
Frequently Asked Questions
How can I tell if my medications are working and decreasing my viral load?
Your provider should closely monitor your viral load during the first few weeks after you start your medication regimen. Typically, if your medications are appropriate, your viral load should start to reach undetectable levels by 16-24 weeks after you begin treatment.
I just tested positive after being sick with primary HIV Infection. At my last clinic visit, my provider started me on medications to keep my “viral set point” low. Are “viral load” and “viral set point” the same thing?
No. Viral load is the amount of HIV in a sample of your blood. Viral set point is the viral load that your body establishes within a few weeks or months after you are infected with HIV.
Some research suggests that if your viral set point is lowered with medications, the progression of your HIV disease may be slower and less severe, your immune function may be preserved longer, and the risk of viral mutation (which is how new strains of HIV are created) may be lowered.
Last revised: 08/06/2009